Immunology Flashcards
1
Q
What cytokine family does IL-31 belong to and which receptors?
A
IL-31 belongs to the IL-6 cytokine family and is secreted primarily by activated CD4+ helper T cells.
IL-31 acts via a heterodimeric IL-31 receptor and the oncostatin receptor (OSMR).
In dogs, IL-31 can be secreted by T cells after allergen exposure or exposure to bacterial antigens. IL-31 activates the JAK STAT pathway as well as the mitogen activated protein kinase pathway in canine cells.
2
Q
L-13 is elevated in (disease) but not in (disease)?
A
IL-13 is elevated in TEN not EM
3
Q
Define cytokoines?
A
Cytokines are a broad and loose category of small proteins important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrine, paracrine and endocrine signaling as immunomodulating agents.
4
Q
_____ is known to be a major regulatory factor in the production of IgE
A
IL-4
5
Q
___ cytokines may play an important role in the acute phase, whereas ___cytokines may be more relevant in the chronic phase.
A
TH2
TH1
6
Q
Canine keratinocytes have been shown to produce pro-inflammatory agents such as (list 3) in response to Der f1 and LPS?
A
granulocyte macrophage colony-stimulating factor
IL-8
Tumor Necrosis factor
7
Q
What is thymic stromal lymphopoietin?
A
Is is an IL-7-like cytokine that stimulates dendritic cells to induce naïve T cells to differentiate into TH2 like cells.
(IL4, 5 and 13 in humans/IL-4, 13, 31 in dogs
8
Q
Damaged keratinocytes produce more ____ and ____ which skews toward a Th2 response, with IgE production and allergic inflammation.
A
TSLP
Il-33
9
Q
What is the role of IL-23?
A
Upregulates IL-22 by Th1, Th17, Th22
Upregulates IL-17
10
Q
What is the main role of Tarc in allergic inflammation?
A
Chemokine that dendritic cells produce TARC which recruits CD4 helper T cells to skin.
11
Q
What is the role of Th2 cytokines in dysregulation of skin barrier function?
A
Decrease expression of tight junction proteins
Decrease expression of filaggrin
- Increase skin pH (increased proteolytic activity
which degrades ceramides and allows for deeper
penetration of allergens)
- Decreased extrusion of lamellar bodies which leads
to decreased AMP, increase staph colonization and
more inflammation
12
Q
What chemokines and cytokines are produced by keratinocytes?
A
IL-1, iL-6, IL-7, IL-8, IL-10, IL-12, IL-15, IL-18, IL-20, TNF, IFN (alpha, beta and gamma)
13
Q
NK cell can only recognize and detroy a target cell if it fails to express ____ molecules of MHC
A
class I
14
Q
What are the two key types of dendritic cells within the skin immune system?
A
Langerhan Cells (Epidermis) Dermal dendritic cells (Dermis)
15
Q
What is the main role of Th1 cells?
A
Helps cell-mediated/cytotoxic responses against viruses or intracellular pathogens
Produce IFN and mediate cell-mediated immunity involving the activation of cytotoxic T cells, NK cells and phagocytic cells.
16
Q
What in the main role of Th2 cells?
A
Helps antibody responses against extracellular pathogens
17
Q
What is the main role of Th17 cells?
A
Helps responses against fungi
18
Q
What is the main role of T-reg cells?
A
Switches off responses that are no longer required
19
Q
What cytokine(s) do CD4+ Th1 lymphocytes produce?
A
- IFN-gamma
- IL-2
- TNF-alpha
20
Q
What cells do Th2 lymphocytes stimulate? Through what cytokine(s)?
A
B cells
IL-4, IL-5, IL-6, IL-9, IL-13
21
Q
What are the surface membrane toll-like receptors of the dendritic cell?
A
TLR-2
TLR-4
TLR-5
22
Q
What cytokine(s) do CD4+ regulatory T cells produce?
A
TGF-beta
IL-10
IL-35
23
Q
What are the cytoplasmic toll-like receptors of the dendritic cell?
A
TLR-3 viral
TLR 7/8 viral
TLR-9 bacterial
24
Q
What are the three signals required for activation of a naive Th0 lymphocyte?
A
1) recognition of antigenic peptide-MHC II complex by the T-cell receptor/recognition of MHC II by the T cell CD4 molecule
2) other surface interactions
3) cytokines produced by the APC binding to receptors on the T cell membrane
25
Langerhans’ Cell
Primary APC monitoring the body’s external surfaces
Langerin+CCR6+CCR7+/-, radioresistance, slowly self-replicating, highly responsive to CCR6 agonist macrophage inflammatory protein-3α (CCL20)
Mononuclear, dendritic, antigen-presenting cells located basally or suprabasally
26
Langerhans’ Cell Location
Reside in the suprabasal layers of the epidermis, wedged in between and in close contact with keratinocytes
Account for 3 to 5 % of all nucleated cells in the epidermis of mice and humans
Arranged in a network that occupies the interstices between neighboring keratinocytes
Found in the epidermis, dermis, lymph nodes (usually in the thymus-dependent areas), thymus, mucosal surfaces (oral cavity and bovine rumen)
Distribution varies among species and strains within species
Mouse tail skin & hamster cheek pouch virtually no LCs
Humans: high densities on the head, face, neck, trunk, and limb skin
Density decreases with age, chronic actinic damage
Anchored to surrounding keratinocytes by E-cadherin-mediated homotypic adhesion
Newly discovered population of Langerin+ DCs in the dermis and skin-draining lymph nodes
Distinct phenotypic and mitotic capacities
Dermal Langerin+ LCs do not appear to simply be epidermal LCs en route to the draining lymph node
27
Langerhans’ Cell Detection
```
Appear as “clear cells” on routine hematoxyline and eosin stained sections
Gold chloride (aureophilic) impregnation allows better visualization and differentiation from other dendritic cells (melanocytes)
```
28
Langerhan Cells Morphology
Stellate appearance (why they were initially thought to be of neural origin)
Long cytoplasmic processes that occupy as much as 25% of the surface area of the epidermis
Form a continuous cellular network that surveys the epidermis for foreign antigens via extended dendrites
Convoluted nuclei; clear cytoplasm with no tonofiliments or desmosomes; dose have vimentin
Initially identified by an electron dense organelle: Birbeck granule
29
Birbeck granules
Also known as Langerhans’ granules
Classic ultrastructural feature of LCs detected in some humans and some animal species by electron microscopy
Consist of superimposed membranes separated by repetitive zipper-like striations
Form by invagination of the plasma membrane and bound antigen
Rod-shaped body with central striations and a saccular terminus (vesicle at one end of the membrane)
Creating a unique tennis-racket appearance
Identified in feline, bovine, ovine, caprine and equine epidermal LCs
****Not found in dog or pig LC (but still have dendritic ATPase + cells)
Function: unclear, but likely includes receptor-mediated endocytosis and transport of cellular materials into the extracellular space
Function in antigen presentation
30
Birbeck granules: Species specifics
Birbeck granules have been IDed in feline, bovine, ovine, caprine and equine epidermal dendritic cells
In horses: felt to have more than one type – In recent study, lesions for “Kasen” revelaed LCs in the spinous layers had several granules and LCs form the DEJ had a few
In cattle, stain best with alkaline phosphatase
In sheep, stain best with acetyle cholinesterase
In Guinea pigs, mice and humans, stain best with adenosine triphosphatase
In mice & dogs, stain well with non-specific esterase
31
Surface molecules expressed by LCs
```
DOGS: CD1a,b,c, CD11a,c, CD18, CD45, ICAM-1, MHC class II, vimentin positive
CD4 and CD90 (Thy1) negative
```
CATS: CD1a, CD4, CD18, and MHC class II positive
32
CD1a
First monoclonal antibody that clearly identified LCs bound to CD1a
A major histocompatibility complex I-like molecule
Member of the group 1 CD1 proteins (CD1a, CD1b, CD1c)
Presents microbial lipids to T cells
Can be found in high concentration in the Birbeck granule
33
Langerin (CD207 a well-known surface receptor on Langerhans cells (LC), belongs to the ______ family and constitutes a major pathogen binding receptor able to regulate both innate and adaptive immune responses
C-type lectin receptor (CLR)
Used more recently to specifically recognize LCs – single best feature discriminating LCs from other cells
Expressed in virtually all LCs in stratified epithelia.
A membranous C-type lectin with mannose-binding specificity
Bind mannose and related sugar via Ca+ dependent manner through its carbohydrate-recognition domain. Plays important role in the internalization of cell surface antigens
Recognizes mannosylated ligands found on the surface of a wide range of pathogens, including viruses, bacteria, fungi, and protozoa
Following receptor mediated endocytosis, traffics with CD1a to the Birbeck granule
***Mutation in langerin -- deficiency of Birbeck granules
Down-regulated upon LC maturation but detectable levels remain in LCs once they reach cutaneous lymph nodes
34
FcεRi
A high-affinity receptor for IgE
Presence on LCs at antigen presention in the LN
Associated with Th2-type immune responses characterized by IL-4, IL-5, and IL-13 producing T cells
Aggregation of this receptor on LCs induce the release of various chemotactic factors - IL-16 and monocytes chemotactic protein
35
Type II transmembrane cell surface receptor
membranous C-type lectin with mannose-binding specificity
| Bind mannose and related sugar via Ca+ dependent manner through its carbohydrate-recognition domain
36
C-type lectin receptor
a receptor that binds glycosylated ligands and has many roles, such as in cell adhesion, endocytosis, natural-killer-cell target recognition and dendritic-cell activation
37
Movement of LC
Epidermal LCs are continuously replaced from a resident precursor pool throughout life under steady-state conditions
Half-life (non-inflamed murine epidermis): 2 – 3 months
Two non-mutually exclusive pathways fro repopulation:
1. LC division within the epidermis
2. Differentiation of LCs from skin-resident or blood-borne precursors
38
Describe migratory LCs
LCs migrate to draining LNs in the steady state
After leaving the epidermis - migrate through dermal lymphatic vessels and localize in T-cell area of skin draining lymph nodes
Upregulate and redistribute MHC class II molecules, upregulate the expression of CD40 and CCR7 (CC-chemokine receptor 7 - essential for LC migration to skin draining LNs)
39
LC Maturation
Best characterized in context of inflammation but also can occur in the steady state
When stimulated, LCs retract the dendritic processes, detach from surrounding epithelial cells and migrate out of the epidermis
The capacity to process protein antigens via MHC class II pathway is down-regulated, however the ability for T-cell co-stimulation is improved
Review:
↓ expression of Fc Receptors, Birbeck granules, and E-cadherin decreases the ability for antigen capture & processing
LPS, TNF-α lead to an upregulation of CCR7 that induce migration from the skin to the lymph node by ligating chemokines MIP-3β and SLC
β2 integrins are upregulated to help binding to other cells and ECM
40
Functional properties of LC
LCs carry antigens, including self-antigens, from epidermis to the draining LN
Functions as antigen-processing cells in the epidermis, having the capability to process native antigens and activate memory and effector-T cells monitoring the skin surface
After LC has migrated from the epidermis, LC alters phenotypically, showing a decrease expression of endosomal antigens and acquiring molecules which enable it to interact with unprimed T cells
One of these molecules is ICAM-1
41
LCs: T cell stimulation
1. APCs present the processed protein/glycolipid using MHC class I and II and CD1; which in turn interact with TCR on CD4+ and CD8+ T cells
2. Accessory molecules of the B7 family creates co-stimulatory signal
B7 (CD80) binds CD28 on the lymphocyte
CD40 binds CD40L on the lymphocyte
Other co-stimulatory molecules include:
ICAM-1 (CD54) that binds to LFA-1 (CD11a/CdD18)
LFA-3 (CD58) binds to CD2 (LFA-2)
42
LC: Immune Tolerance
LCs have a role in the transport and presentation of skin antigens to the skin-draining LNs under steady-state conditions
Treg cells are induced by immature DCs key role in maintaining tolerance to self-antigens in the periphery; exact mechanism is unknown
43
Dermal DCs
Reside in the dermis
Do not have Langerin expression and Birbeck granules
Express more MHC class II molecules and lack phagolysosomes when compared to macrophages
During inflammatory conditions, DC types not normally cutaneous residents (plasmacytoid DCs) will appear
No single or specific marker for these cells; phenotypically less well characterized
CD11c – probably best tool we currently have to identify them
CD1b and CD1c
CD90 also stains for dermal dendritic cells, not LCs
44
CD11c-
indicates that these may be derived from circulating DC precursors migrating into the skin due to inflammatory and chemotactic signals
45
BDCA-2
The only marker that is exclusive for pDCs
46
Follicular Dendritic Cells: (FDCs)
Cells with membranous projections present in the germinal centers of lymphoid follicles in the lymph nodes, spleen and mucosal lymphoid tissues
Not derived from precursors in the bone marrow and are unrelated to dendritic cells that present antigens to T lymphocytes
Trap antigens complexed to antibodies or complement products and display these antigens on their surfaces for recognition by B lymphocytes
This process is important for the selection of activated B lymphocyte who antigen receptors bind the displayed antigens with high affinity
47
Dendritic cells and disease states
| 'Pathogenesis in contact hypersensitivity'
Sensitization phase: a low molecular weight electrophilic/hypdrophilic haptens penetrate the skin and form hapten-protein complexes with epidermal carrier proteins = the complete antigen
These binding proteins are likely cell surface molecules on LC (MHC class I and II molecules) - LC maturation occurs
LCs migrate to the LN, where the antigen is presented to T cells that then develop into Th2 cells secreting IL-4, IL-5 and IL-13 .
These cytokines lead to activation of eosinophils and isotype switching and IgE production B cells.
Mast cells degranulate upon cross-linking of surface-bound IgE antibodies by the allergen.
Endothelial cells are activated and express adhesion molecules that allow binding and exocytosis of inflammatory cells
T cells secrete cytokines and eosinophils release their granules leading to inflammation and clinical signs
• Important role in afferent phase (Induction/presentation and processing of antigen) of contact hpersenistivity (a type IV hypersensitivity reaction)
• Immunological reaction to hapten
o Poison Ivy Wandering jew plant Jasmine Cedar Chips
o Medications Neomycin Thiabendazole Tretinoin Miconazole
• Hapten-protein complex binds to epidermal Langerhan’s cells, dendritic cells and is then pinocytosed.
• Antigen is digested into small polypeptides that bind to MHC II and are transported to cell surface.
• Langerhans cells dendritic network become rounded and decrease in number after contact with chemical sensitiser and produce IL-1β
• Migration to lymph node occurs within 2-4hr and there are changes in cellular adhesion molecule expression to facilitate this.
• Presentation of MHCII peptide-Ag to naïve T cells leads to clonal proliferation of specific T cells in lymph nodes
• Effector and memory T cells are then released in to circulation
48
The main role of ____ is to activate allergen-specific T lymphocytes via MHC II / T cell receptor interactions.
LCs
49
Epidermal LC are _____ in number in skin biopsies from lesions of human AD and canine AD.
Increased
50
LC possess ______ which facilitates the uptake of IgE associated allergens.
FcεRI (high affinity IgE receptor)
51
A recent study demonstrated that canine LC express ____ chains but not the ____ chain of FcεRI which is identical to humans
α and γ
β chain
(Murine LC do not express functional FcεRI (only express γ chain; therefore canine is a better model) (Bonkobara et al 2005 Vet Research Communications 29;499-505)
52
Insect bite hypersensitivity in the horse have an increased number of what cell type?
increased number of LC
53
LCS and interaction with UV
Following UV light exposure, epidermal LCs are decreased in density and altered morphologically, resulting in an immunosuppressive environment and antigen-specific tolerance
UVB causes LC apoptosis leading to a dose-dependent decrease of LCs in the skin
UVAI – induces emigration of DDCs from the skin
UVAII – decreases the number of LCs
54
LCs and drug interaction with GC, CSA, Tacrolimus and imiquimod
GCs (topically or systemic) depress LCs numbers and function
Tacrolimus/pimecrolimus causes apoptosis-induced depletion of T cells and decrease of inflammatory DCs
CsA impairs DC migration by regulating chemokine receptor expression and inhibiting COX-2 expression
CsA and tacrolimus inhibit MHC-restricted antigen presentation pathways of DCs
Imiquimod induces migration of LCs from skin to draining LN
55
What is the most reliable way to identify LC?
Electron microscopy; antibody stain Lag-antigen
56
What are LC Histochemical Staining in different species?
Cow LC’s stain best for ALP
Sheep LC’s stain best for acetyl cholinesterase
Human, guinea pig and mouse LC’s stain with ATP’ase
Mice and Dogs also stain with non-specific esterase
57
Antigen is encountered and processed by LC and then presented (altered) by the MHC complex. Cellular adhesion that allows this is via ____ and ____.
ICAM-1 & LFA (lymphocyte function-associated antigen)
58
What are LFAs?
are in the immunoglobulin superfamily of adhesion molecules
***Also the T-cell LFA-2 (also called CD-2) binds to LFA-3 on APC
59
What is ICAM-1?
is an integrin from the surface of most hematopoietic cells and antigen presenting cells
60
Histiocytoma
a. Early lesions: Phenotype similar to immature LCs
i. –High levels: CD1, E-cadherin
ii. –Low levels: MHC I and II
b. Regressing lesions: Phenotype similar to mature LCs
i. –Down-regulation CD1, E-cadherin
ii. Up-regulation MHC I and II ICAM-1
61
LC in delayed hypersensitivity
Antigen or hapten associates with MHC II of LC’s
These travel to regional LN and settle in paracorticol T-cell area
T-cell activation occurs
Activated T-cells are supported by continuous release of IL-1 by the LC
Activated T-cells release IL-2 which results in continued proliferation of activated T-cells
These are released into circulation and when an individual is challenged keratinocytes release cytokines (IL-1, IL-8 and TNF-α), which results in increased endothelial adhesion molecule expression (L-selectin/ELAM 1), which promotes activated memory T-cell migration into the skin.
Migrating T-cells release, among others, γ-interferon, which promotes continued keratinocyte cytokine release. Both CD4+ and CD8+ T cells are present in contact hypersensitivity.
62
What are 'touch spots'?
areas within glabrous skin where MCs are clustered near unmyelinated sensory nerve endings at the bottom of rete ridges
Innervated by a single, slowly adapting type 1 nerve fiber
Other terms: hair disc, touch dome, touch corpuscle, Iggo disc
In hairy skin and whisker pads – concentrated to rete ridge and outer root sheath of hair follicle at sites of attachment of the arrector pili muscle
63
Function of merkle cells?
Characterized as slow-adapting mechanoreceptors, which are confined to the tylotrich pads of mammalian skin
Slowly adapting type 1 neurons – a subset of Aβ (mechanoreceptive fibers) touch receptors with a low threshold value
Other functions suggested:
1. Neuroendocrine functions such as influencing cutaneous blood flow and sweat production via the release of vasoactive intestinal peptide
Can produce: serotonin, enkephalin, VIP, somatostatin, calcitonin gene-related peptide
64
Merkel Cells are innervated what what type of fibers?
Innervated by myelinated type I nerve fibers, which forms a structure called a Merkel cell-neurite complex
65
Tylotrich pads
Tylotrich hairs
Special type of tactile hair found in mammalian skin
Larger then regular hair follicles
Contain a single stout hair and an annular complex of neurovascular tissue that surrounds the follicle at the level of the sebaceous glands
Each tylotrich hair follicle is associated with a Tylotrich pad
Tylotrich pads are composed of a thickened and distinctive epidermis covering a convex area of fine highly vascular and innervated connective tissue
66
Immunohistochemical markers of the Merkel cell
K8, K18, K19, and K20 keratin peptides
| K20 is restricted to Merkel cell in skin and therefore is most reliable marker
67
Merkel Cell Tumors
This is a primary cutaneous neuroendocrine tumor
Can be either malignant and metastatic or benign with rare recurrence after surgery
Commonly found on lips, ears, digits, oral cavity
Usually rapid growing +/- ulceration
Extremely rare in cats- case reports of benign nasal tumor and malignant tumor in dorsolateral cervical region
68
Function of merkle cells?
Slow adapting mechanoreceptors
Type I mechanoreceptors aka myelinated type I nerve fibers
Located in sites of high-tactile sensitivity
Unmyelinated nerve endings which are slow adapting touch receptors are associated with Merkel’s cells
Influence cutaneous blood flow
Influence sweat production
Via release of vasoactive intestinal peptide
Coordinates keratinocyte proliferation
Maintains and stimulates stem cell population of the hair follicle
Controls hair cycle
69
What does gamma delta refer to?
γδ refers to a type of T cell receptor
Disulfide-linked heterodimer; expressed on T cells that don’t have the more traditional αβ T cell receptors
γδ TCR is associated with CD3 and ζ proteins just like lymphocytes with αβ receptors
70
How are gamma delta T cells made?
• Develop in the thymus
- Lineage separate from the αβ T cells but they have a common precursor
• There is very little diversity in the γδ TCR, which suggests that the ligands (the stuff this receptor recognizes) are invariant and conserved
But still adapative since rearrange TCR genes and develop memory
71
Who has gamma delta T cells?
Epithelial tissues of certain species
50% of the lymphocytes in the small bowel mucosa of mice and chickens are γδ T cells.
Majority of T cells in mouse skin are γδ T cells
72
What is the function of gamma delta T cells?
Do not recognize MHC-associated peptides
Some γδ T cells can recognize small phosphorylated molecules, alkyl amines or lipids such as those found in mycobacteria and other microbes when they’re presented on “class I MHC-like” molecules
Some studies have shown that M. tuberculosis can stimulate γδ T cells.
Other γδ T cells recognize protein or nonprotein antigens that do not require processing or an APC.
Antimicrobrial immunosuvalience
Produce IFN gamma
Cytotoxic functions
Antigen Presentation to CD8+ and CD4+ cells
Anti-Tumor Immunosurveilance
Produce IFN gamma
Down regulate protumor alpha beta T cells
Have NKG2D molecule surface molecule that targets cellular destructions
T regulatory Functions
Expression of Fas ligand
Wound healing
73
Clinical importance of gamma delta T cells?
Canine epitheliotrophic cutaneous T cell lymphoma is most often caused by T cells that express the γδ receptor rather than the αβ receptor.
Lymphocytes that infiltrate the epidermis and dermis of atopic dogs can express both γδ and αβ receptors. In the dermis of atopic dogs, there are 10x more αβ than γδ receptors. In the epidermis of atopic dogs, some cases have a mostly γδ lymphocyte population. People with AD do not have an increase in γδ lymphocytes in their skin.
Subsets of γδ T-cells are able to produce IL-4 or IFN-γ
γδ T-cells can recognize antigens directly without prior processing
Ruminant γδ T-cells recirculate continuously between epithelial surfaces, such as skin or intestinal epithelium, and the bloodstream
74
Birbeck granules
variously described as being zipper, rod, flask or tennis racket like in appearance. They form by invagination of the plasma membrane and bound antigen, thus providing the morphologic description of the mechanism by which Langerhan cells internalize surface-bound antigen for processing and representation at the surface.
75
Langerhan cells are aureophilic meaning....
They stain with gold chloride. Unlike Langerhan cells in humans, those in dogs and cats are S-100 protein and ATPase negative.
76
In dogs, Langerhan cells are positive for what markers?
```
CD11a,c
Vimentin
CD1a,b,c
CD18
CD45
ICAM1
MHC2
```
77
How can you distinguish Langerhan cells from dermal dendritic cells?
They are CD4 and Thy1 (CD90) negative
78
In cats, Langerhan cells are positive for what markers?
CD1a, CD18, CD4 and MHC2
79
Following UVL exposure, Langerhan cells are ____ in density and altered morphologically.
decreased
80
What are examples of PAMPs?
peptidoglycan, lipopolysaccharides (LPS), glycolipids, and mannin-rich carbohydrates.
81
On what cells are TLRs found?
macrophages, eosinophils, mast cells, dendritic cells, and epithelial cells.
82
What is an iron binding protein found in the stratum corneum where its main affect is to limit the amount of free iron build up which can predispose to bacterial infections?
transferrin
It can also reduce the binding of gram-positive and ram-negative bacteria to surfaces.
It is currently not known if this mechanisms is relevant to canine and feline skin BUT transferrin has been show to inhibit growth of Malassezia in vitro.
83
What is a common peptide with antibiotic functions produced by the epidermis?
defensins
These are systemic-rich proteins that are also present in neutrophil granules. Synthesis of defenses is unregulated in response to inflammatory cytokines such as IL-1 and TNF. Defensins are similar to broad spectrum antimicrobials - able to kill bacteria and fungi.
84
Expression of what antimicrobial peptide was down regulated in skin of atopic drop and may be therefore a link to the increased incidence of bacterial infections in atopic dermatitis.
Canine b-defensin
85
This process known as ____, it is the first step in any infection. Bacteriahave specific molecules on their surface known as ___ that allow them to do this.
adhesion
86
List common adhesions on staphylococci:
teichoic acid
lipoteichoic acid
fibronectin binding proteins
laminin binding proteins
***these molecules bind to various proteins on the host such as fibronectin, laminin and collagen.
87
If the basic barrier mechanisms of the epidermis are unable to prevent injury to the host, the innate immune system has a number of other defense mechanisms that can be used to provide protection against parasites or infectious agents. The mechanisms include:
Activation of complement
Recruitment and activation of phagocyte cells (neutrophils and macrophages)
Recruitment of eosinophils
activation of intraepithelial lymphocytes and natural killer cells
production of cytokines and chemokine
88
____ system is a series of plasma proteins that exist in the quiescent state until they are activated. The role of this system is to assist the immune system in eliminating pathogenic bacteria.
Complement
89
The complement cascade can be activated by three distinct pathways
1. classical pathway
2. alternative pathway
3. lectin pathway
90
Describe the classical complement pathway
The classical pathway is activated by antibody-antigen complexes, which bind to the first complement component, C1. Is the subsequent complex series of steps, C4 and C2 components of complement bind to C1 forming the active enzyme = C3 convertase
91
What enzyme catalyses conversion mod the third complement component (C3) into C3a and C3b?
C3 convertase
92
What complement protein is a chemoattractant for neutrophils and can activate mast cells, whereas __ can opsonize bacteria and promote phagocytosis.
C3a
| C3b
93
What protein activates that membrane attack complex (MAC) , which is a cylindrical structure composed of complement components 5,6,7,8,9. The membrane attack complex can 'punch holes' in the membrane of certain types of bacteria, resulting in cell death.
The membrane attack complex is initiated when the complement protein C5 convertase cleaves C5 into C5a and C5b.
94
How is the alternative complement pathway activated?
It is activated by direct interaction between the surface of a microbe and C3b, which is generated in the serum by slow, spontaneous hydrolysis of C3. Once bound, the C3b catalyses further conversion of C3 into C3b.
95
Describe the lectin pathway
A plasma lectin bind to a mannose residue on the surface of a microbe and activated c1 in the absence of antibodies. The pathway is subsequently the same as the classical pathway.
96
Deficiency in C3 occurs in both humans and what breed of dogs? This results in increased susceptibility to pyogenic infections.
Brittany spaniels
97
Deficiencies of the components that make up the membrane attack complex only lead to increase rates of infection by what organism, leading to meningitis in humans?
Neisseria
98
To eliminate bacteria, initially, what circulating cells are first recruited to the site of infection?
neutrophils and monocytes
99
The initial inflammatory response is triggered by resident tissue ____ that detect microorganisms and secret the pro inflammatory cytokines IL1 and TNFa.
macrophages
100
What cytokines lead to the up regulating of adhesions molecules on blood vessel walls, including selecting and interns, which can bind to ligand on the inflammatory cells.
IL-1 and TNFa
101
What adhesion molecule binds to carbohydrate lights on the phagocytic cell surface with low affinity, causing the cell to slow down and roll along the endothelium?
E-selectin
102
High-affinity interactions between what interns and their corresponding ligands on inflammatory cells will result in firm binding, allowing the cells to stop.
ICAM1/VCAM1 with their corresponding ligands on LFA1 or CD11a/CD18 and macrophage activation complex 1 (MAC1 of CD11b/CD18).
Once their flow has been arrested, the phagocytes migrate through the intercellular space of the blood vessel wall and travel along a chemokine concentration gradient toward the site of infection.
103
______ are chemotactic cytokines that stimulate movement and migration of leukocytes from the blood into tissue. While migrating through tissues, the inflammatory cells adhere to components of the extracellular matrix such as fibrin and fibronectin.
chemokine
104
___ has been shown to be a potent chemoattractant for canine neutrophils.
IL-8
105
What are classes of receptors that can bind microorganisms and mediate phagocytosis of cell activation?
1. Mannose and other C-type lectin-like receptors.
2. Scavenger receptors
3. Receptors for opsonization
4. TLRs
5. Seven transmembrane receptors
106
Mannose and other C-type lectin-like receptors
Plasma membranes of phagocytes have receptors, this is a macrophage lectin that can bind to terminal mannose and fructose residues on glycoproteins/lipids. These sugar residues are typically found in bacterial cell walls but are not found in mammalian glycoproteins or lipids. Once the receptor binds to the microbe, it mediated internalization by phagocytosis.
**Lectin receptors bind glycans present in the fungal cell walls.
107
Scavenger receptors
These bind oxidized or acetylated low-density lipoproteins as well as various microbes.
108
Receptors for opsonin
These include FCyRII receptor, which binds microbes that have been opsonized with IgG, and CR1 which binds to microbes that are coated with complement proteins.
109
TLRs
There are at least 10 different types of TLRs, and they respond to various types of pathogens. They recognize PAMPs and bind various microbial molecules wish as LPS, lipoproteins, lipoteichoic acid, zymosan, flagellin, heat chock protein 60, CpG motifs, viral nucleic acids, and double stranded RNA.
Once activated, TLRS initiate a series if intracellular signaling pathways that result in the generation of an inflammatory response.
110
Seven transmembrane receptors
Coupling with G proteins, they are called seven-transmembrane receptors because they pass through the cell membrane seven times. Ligands can bind either to extracellular N-terminus and loops
111
Neutrophils kill microorganisms by forming ____, such as superoxide radicals, that form hydrogen peroxide. In addition to reactive oxygen intermediates, macrophages produce ____ that can combine with hydrogen peroxide to produce highly toxic peroxynitrite radicals to kill microbes.
reactive oxygen intermediates
| reactive nitrogen intermediates
112
Eosinophils are attracted to sites of inflammation by specific chemotactic factors such as:
```
histamine
complement component 5a
leukotriene B4
parasite extracts
chemokines (eotaxin 1 and 2, RANTES)
```
113
The most important function of eosinophils is their secretory function. Eosinophil granules contain a number of important proteins that include:
major basic protein
eosinophil cationic protein
eosinophil peroxide
lysosomal enzymes
***These proteins are toxic to helminths, cells and bacteria and can degranulate mast cells, but they can also cause significant damage to host tissue in hypersensitivity disorders.
114
____ are functionally activate during expulsion of the parasites, releasing large quantities of granule proteases.
Mast cells
| ***mast cells are known to contain TNFa***
115
Mast cells are also involved in wound healing. _____, an important cytokine in wound healing, is a potent chemoattractant for mast cells in vitro. ______ is a chemokine that attracts mast cells to wounded area.
TGFb
| chemokine monocyte chemoattractant protein 1
116
Mast cell derived ___ and ___ can promote fibroblast proliferation, and mast cell extracts cn activate fibroblasts, promoting collagen synthesis and activation of gelatinase A, an enzyme involved matrix remodeling.
TGFb and TNFa
117
TNFa is produced by what cells?
macrophages, activated T cells, NK cells and mast cells
118
IL-1 is produced by what cells?
macrophages, endothelial cells and keratinocytes
119
Antigens that trigger an IgE response are called?
allergens
120
To detect antigens, the body uses what two receptors?
antibodies
| T-cell
121
Define antibodies
These are present on the surface of the B lymphocytes and recognize the antigen in its native three dimensions form. They usually detect a particular part of the protein molecule that is highly immunogenic and situated on the outside of the molecule (immunodominant epitopes)
122
Define T cell receptor
These are situated on the surface of T lymphocytes. They cannot recognize the protein in its native form. The whole antigen must first be processed by an antigen presenting cell in which the protein is broken down into peptides by various enzymes including cathepsin.
123
Describe the four mechanisms the immune system has developed to prevent 'self-reactive' lymphocytes from causing harm.
1. If the host antigens are naturally hidden (eye, testes, SNA) the lymphocytes do not come into contact with them and remain 'ignorant'.
2. When lymphocytes develop in either the bone marrow of thymus, those that react with host antigens are killed by a process known as apoptosis. This mechanism is known as 'clonal deletion' = central tolerance.
3. If autoractive lymphocytes enter the peripheral circulation, the bod can be protected by peripheral tolerance. This is when cells are instructed to undergo apoptosis by tolergenic dendritic cells, or they can become anergic.
4. Autoreactive lymphocytes can also be controlled by regulatory T cells that secrete immunosuppressive cytokines such as IL-10 and TGF-b.
124
The major dust mite allergen for dogs appears to be a high-molecular weight ______, rather than the group 1 and 2 proteinases.
chintinase; This chintinase is present in the dust of D. farinae and it classified as Derf15.
125
What are the major allergens of Japanese cedar?
cryj1 and cryj2
126
Unlike the interaction between antigens and antibodies, T cells are unable to recognize whole proteins. To activate the T-cell population, antigens must first be process and then presented to the T-cell receptor by a ______.
professional antigen presenting cell; in the skin, the main antigen-presenting cells are Langerhan cells (in the epidermis) and dermal dendritic cells (dermis).
127
antigens are phagocytosed by APC and broken down into small peptides within the ____.
phagolysosomes.
128
It is not possible for small peptides to be recognized by the T cell receptor independently; The peptides must first be attached to _______ protein molecule produced inside the antigen presenting cell. These proteins transport the peptides back to the cell surface and present them to adjacent T cell receptors.
Major histocompatibility complex protein molecules
129
MHC complexes, what are the three groups?
MHC1 - codes for proteins found o the surface of most nucleated cells.
MHC2 - codes for proteins usually only found on macrophages and lymphocytes
MHC3- code for a variety of inflammatory molecules including complement, TNF and heat shock proteins.
***only MHC1 and MHC2 are involved in antigen processesing and presentation
130
Canine systemic lupus erythematous is more common in dogs that possess the ______ haplotype.
DLA-A7 MHC haplotype
131
T lymphocytes can be divided into what two groups?
1. Helper T cells possess a surface protein known as CD4, which is the receptor for MHCII molecules.
2. Cytotoxic T cells possess surface protein known as CD8, which is the receptor for MHC1 molecules.
132
Immunostains for ___ can be used to identify T cells.
CD3
133
What are the proteins that can stimulate T cells directly by cross-linking MHC molecules and T-cell receptors at a site away from the peptide being cleft This can activate the lymphocyte and lead to cytokine production and an inflammatory response. This is a special kind of antigenic stimulation.
Superantigens; the best examples are exotoxins produced by S. aureus.
Superantigen production has been demonstrated with staphylococcal enterotoxins A and B being more frequently detected.
134
For the T cell to be activated, a second signal is required. What are second signals?
Second signals are are a series of molecular interactions between adhesion molecules on the two cells and epcifi receptor Wigan interactions. In some cases, cytokine signaling may also be involved. If these signals do not occur, the T cell does not respond.
135
List signal transduction mechanisms within the T cell
G-proteins
tyrosine kinases
mitogen-activated protein (MAP) kinases
***these enzymes can modify the function of proteins and lead to ypregulation of certain cellular mechanisms, resulting in proliferation, cytokine synthesis and secretion.
136
In the case of cytotoxic T cells (CD8), this results in release of ____, _____ and _____. These are capable of killing the target cell in a process known as ______.
perforins, cytotoxic enzymes, cytokines such as TNFa
| cell-mediated cytotoxicity - the main purpose of this to to eliminate virus-infected cells.
137
T helper 1 cells produced predominately what cytokines?
IL2 and IFNy
138
T helper 2 cells proceed predominately what cytokines?
IL-4, 5, 6, 10 and 13
139
Secretion of what cytokine by antigen presenting cells is a potent signal for Th2 development.
IL-4
140
Some parasites secrete substances such as ____, that can direct T cells to develop a Th2 phenotype. Hence, many parasitic infections are dominantly by Th2 response.
PGE2
141
Secretion of what cytokine by antigen presenting cells is a potent signal for Th1 development.
IL-12
Stimulates Th1 differentiation and stimulates synthesis of IFNy
142
In general, ____ response tend to promote cell-mediated immunity and IgG production; while, ___ response tend to promote IgE production and allergic responses.
Th1
| Th2
143
If the B cell interacts with a TH2 type cell, ____ will instruct the B cell to produce IgE instead of IgG. This process is known as ________.
IL4, isotope class switching
144
Molecular interactions between T cells and B cells (second signals)
```
ICAM1 - LFA1
LFA3 - CD2
B7-CD28
CD40-CD40 Ligand
Antibody production - cytokine secretion
```
145
Inflammation causes the skin surface pH to switch from acid or neutral to alkaline. Skin surface pH is typically measure by a _____.
glass electrode technique - pH meter
146
keratinocytes synthesize ______ that form a barrier for innate host protection against microbial pathogens. these peptides appear to function in regulating cell proliferation, extracellular matrix production and cellular immune response.
antimicrobial peptides (cathelocidins and defenses)
147
Chemokines
Source: macrophages, endothelial cells, T cells, fibroblast, platelets
Target: Leukocytes
Effect: Chemotaxis, migration into tissues, activation
148
IFNalpha
Source: macrophages
Target:natural killer cells, tissue cells
Effect: increased expression of MHC1, antiviral state, activation of NK cells
149
IFNbeta
Source: fibroblasts
Target: NK cells, tissue cells
Effect: increased expression of MHC1, antiviral state, activation of NK cells
150
IFNgamma
Source: Macrophages, T cells (Th1, CD8), NK cells
Target: Macrophages, T cells, NK cells, dendritic cells, B cells
Effect: activation of macrophages (stimulates production of reactive oxygen metabolites), T cell differentiation (Th1), B cell class switch to immunoglobulin IgG, expression of MHC1 and MHC2
151
IL-1
Source: Macrophages, endothelial cells and some epithelial cells
Target: endothelial cells, hypothalamus, liver
Effect: activation of endothelial cells, fever, synthesis of acute phage proteins and synthesis of IL-6 (which stimulates the production of IL-17)
152
IL-2
Source: macrophages, T cells
Target: B cells, T cells, NK cells
Effect: Inflammation, proliferation and differentiation of T cells, synthesis of IFNy and IL4, proliferation and differentiation of NK cells, antibody synthesis
153
IL-3
Source: T cells
Target: immature hematopoietic stem cells
Effect: stimulates hemoatopoesis; a mast cell and basophil growth factor.
154
IL-4
Source: Th2 cells, mast cells, basophils
Target: Th2 cells, B cells, epithelial cells, macrophages
Effect: Amplify Th2 development, also B cell class switch and production of IgE, allergic reactions, macrophage activation, GI peristalsis, mucus production = allergic type inflammation
155
IL-5
Source: Th2 cells, mast cells
Target: Eosinophils, B cells
Effect: Activation growth and differentiation of eosinophils, stimulates IgA production
156
IL-6
Source: macrophages, endothelial cells, T cells
Target: Liver, leukocyte progenitors, B cells
Effect: synthesis of acute phase proteins, proliferation of B cells and antibody production, stimulates production of neutrophils, stimulates production of IL-17.
157
IL-7
Source: fibroblast, bone marrow stroll cells
Target: immature lymphoid progenitors
Effect: production of B and T lymphocytes
158
IL-10
Source: macrophages, T cells
Target: macrophages, dendritic cells
Effect: inhibits production of IL-12 and promotes expression of MHC 2 molecules
159
IL-12
Source: dendritic cells, macrophages
Target: Tcells, NK cells
Effect: Th1 differentiation, stimulates synthesis of iFNy
160
IL-13
Source:Th2 cells, basophils, eosinophils, NK cell, T cells, macrophages
Target: B cells, monocytes, dendritic cells. eosinophils, basophils, fibroblasts, endothelial cells, epithelial cells.
Effect: increased mucus production, increased IgE synthesis, fibroblast proliferation
161
IL-15
Source: macrophages, others
Target: NK cells, T cells
Effect: Proliferation (NK cells and T memory CD8 cells)
162
IL-17
Source: T cells
Target: leukocytes, epithelial cells
Effect: Stimulates production of chemokines, antimicrobial peptides, inflammation, neutrophil responses
163
IL-18
Source: macrophages
Target: NK cells, T cells
Effect: IFNy synthesis
164
IL-21
Source: T-cells
Target: B cells, T cells, NK cells
Effect: B cell growth, generation of follicular helper T cells, proliferation of T and NK cells
165
IL-22
Source: T-cells
Target: epithelial cells
Effect: Stimulates synthesis of antimicrobial peptides, promotes barrier function
166
IL-23
Source: macrophages, dendritic cells
Target: T cells
Effect: maintenance of IL-17 producing cells
167
IL-25
Source: Th2 cells
Target: phagocytes, T-cells
Effect: Stimulates production of IL4, IL5, IL13; increased expression of migration inhibition factor (MIF) (immobilization of phagocytes at the site of infection).
168
IL-27
Source: macrophages, dendritic cells
Target: T-cells, NK cells
Effect: Th1 differentiation, IFNy synthesis
169
Granulocyte colony-stimulating factor
Source: macrophages, fibroblasts, endothelial cells
Target: granulocyte progenitors
Effect: stimulates granulocyte production
170
Granulocyte-monocyte colony-stimulating factor
Source: T cells, macrophages, endothelial cells, fibroblasts
Target: Myeloid progenitors , macrophages
Effect: Stimulates granulate and monocyte proaction and macrophage activation
171
Monocyte colony stimulating factor
Source: Macrophages, endothelial cells, bone marrow cells, fibroblasts
Target: monocyte progenitors
Effect: stimulates monocyte production
172
Stem cell factor (c-kit ligand)
Source: bone marrow stromal cells
Target: hematopoietic stem cells
Effect: stimulates hematopoiesis
173
TGF-b
Source: T cells, macrophages, others
Target:T cells, B cells, macrophages, fibroblasts
Effect: Inhibition of T cell growth and effector functions, inhibition of B cell proliferation, inhibition of macrpahge activation, stimulation of angiogenesis, increased collagen synthesis
174
TNF
Source: macrophages, T cells
Target: Endothelial cells, neutrophils, hypothalamus, liver, muscle, fat, other cells
Effect: Stimulates inflammation, recruitment of neutrophils and monocytes, synthesis of chemokines, synthesis of IL-1, apoptosis of some cells,
175
IL-8
Source: produced by macrophages and other cell types such as epithelial cells, airway smooth muscle cells and endothelial cells.
Target: induces chemotaxis in target cells, primarily neutrophils but also other granulocytes, causing them to migrate toward the site of infection. IL-8 also stimulates phagocytosis once they have arrived.
Effect: neutrophil chemotactic factor, stimulates angiogenesis
*Endothelial cells store IL-8 in their storage vesicles, the Weibel-Palade bodies.
176
List all cytokines produced by keratinocytes
Interleukins: IL1a, IL-1b, IL1RA, IL-6, IL-7, IL-10, IL-12, IL-15, IL-18, TNF-alpha
Chemokines: IL-8, Gro-alpha, MCP-1, MIP-2, IP-10, RANTES
Colony Stimulating Factors: GM-CSF, M-CSF
Growth Factors – TGF-alpha, TGF-beta, KGF, PDGF, NGF, SCF
Angiogenic factors; bFGF, VEGF.
177
Describe how NK cells are able to induce apoptosis
No MHC-1 ? ........and you get introduced to the
Natural Killer Cells
Fas-FasLigand apoptosis
Perforins pores granzyme enter cell
Triggers apoptosis by cystosolic capsase pathway
*****MHC-1 inhibits apoptosis by NK cells
178
MHC expression on keratinocytes
MHC-I presentation is higher than on LC
Rapid cytotoxic T-cell response and apoptosis of keratinocytes if anything out of the ordinary
Role in contact hypersensitivity, herpes viral simplex lichenoid T-cell infiltrative diseases
MHC-II presentation
Not constituitive
IFN-gamma can induce expression converting keratinocytes into Antigen Processing Cells
May play role in development of atopic dermatitis
179
PAMPS
Not found on mammalian cells
Often vital for survival of the pathogenic organism
Example: Lipopolysaccharide in Gram neg bacteria
180
PAMP receptors
Secretory – act as opsonins for complement activation
Endocytic – mediate phagocytosis
Toll-like Receptors (TLR)
Transmembrane cell signals
Activate inflammation via the NF-kB cascade
181
Cytokines that are considered regulators of innate immunity
Citizen Whistleblowers
| TNF-alpha, IL-1, IL-12
182
Cytokines that are considered regulators of adaptive immunity
T-lymphocytes
| IL-2, IL-4, IL-5, IFN-gamma
183
Cytokines that are stimulators of hematopoiesis
Growth factors and colony stimulating factors that promote proliferation and differentiation of leukocytes
IL-3, GM-CSF
184
Cytokines that increase B cell proliferation
Multiple cytokines have the same or overlapping biological action (Il-4, IL-5, IL-13 all increase B-cell proliferation)
185
IFNy inhibits which cytokine?
IL-4
186
TNF mediates what two basic responses?
Gene Transcription
NF-kB pathway
Up-regulate mediators of inflammation
Apoptosis
- Capsase-8
187
TNF-alpha and Apoptosis
TNF-alpha activates capsase-8
Intracellular cascade – cell death
Weak compared with NK-cells and Fas
TNF-alpha upregulates Bcl-2
Acute stage: Bcl-2 blocks apoptosis of stimulated neutrophils and macrophages
Late stages: IL-10 (Debbie Downer Cytokine) shifts balance to promote apoptosis of neutrophils/macrophages
188
Th 1 Cytokines
IL-2
IL-7
IL-12
IFN-gamma
189
IL-2
IL-2 receptors on T-cells
Promotes differentiation of NK cells
Promotes antibody synthesis by B-cells
190
IL-2 receptors on T-cells
Induces cell cycle from G1 to S phase
Induces Bcl-2 (antiapoptosis)
Up-regulates IL-2 receptors on T-cells
Stimulates IFN-gamma
191
JaK/STAT 4 subtypes
```
4 subtypes
JaK1
JaK2
JaK3
Tyrosine Kinase 2
```
192
NF-kB Pathway
```
IL-1
TNF-alpha
Toll-like receptors
Any damage to keratinocytes
Oxidative, UV radiation, protein kinase C
```
193
Why is IL-10 a 'brake'?
Inhibits IL-12 and TNF-alpha
Inhibits INF-gamma
Inhibits costimulation of MHC-II
Inhibits T-cells and Macrophages
194
IL-13 is similar to which cytokine?
Similar to IL4
| Except doesn’t polarize Th2 v Th1
195
What TLR has been the most implicated in host defense against S. aureus?
TLR2 is expressed on the surface of numerous cell types in the skin, including ker- atinocytes, Langerhans cells, monocytes/macrophages, dendritic cells, mast cells, endothelial cells, fibroblasts, and adipocytes.. TLR2 heterodimerizes with TLR1 and TLR6 to recognize tri- and di-acyl lipopeptides, respectively. TLR2 also recognizes S. aureus peptidoglycan (PGN), with CD14 and CD36 acting as TLR2 co-receptors
196
TLR2 also recognizes S. aureus peptidoglycan (PGN), with ____ and ____ acting as TLR2 co-receptors
CD14 and CD36
197
NOD2 is an intracellular cytoplasmic receptor that can recognize what S. aureus peptidoglycan breakdown product?
muramyl dipeptide
NOD2 receptors are able to interact with muramyl dipeptide and trigger signal transduction mechanisms
198
Both TLR2 and NOD2 derived signals within keratinocytes lead to activation of what two transcription factors. These transcription factors acti- vate the keratinocyte, leading to the production and secretion of IL-1 and antimicrobial peptides.
nuclear factor (NF-KB) and mitogen-activated protein kinases
199
Once IL-1B (inducible form of the cytokine) is triggered - this sounds the alarm for what events to occur?
Subsequent transduction via the myeloid differentiation primary response protein 88 (MyD88) and interleukin-1 receptor-associated kinase 4 (IRAK4) signaling pathway triggers the activation of NF-kB. The end result is the further production of cytokines (such as TNFa, IL-6, IL-7 and IL- 18), chemokines and mediators that prepare the host for the battle ahead.
200
How do antimicrobial peptides work against Staphylococcal infection?
The two major groups are defensins and cathelicidins.
AMPs (cationic) attach to Staphylococci due to their high affinity for anionic molecules on the microbes’ surface and lead to membrane damage, disruption of the ion gradient and sub- sequent bacterial death
201
What is the only cathelicidin produced in humans?
LL-37 is also produced by human keratinocytes and plays a role in the defense against skin pathogens.
Another antimicrobial molecule produced by human keratinocytes with anti-staphylococcal activity is RNase 7.
Activation of TLR2 on keratinocytes by harmless commensal organisms such as Staphylococcal epidermidis can promote pro- duction of AMPs, which in turn can provide protection against Staphylococcus aureus
202
What role are mast cells likely to play in the defense against staphylococci?
First, the release of histamine will have an immediate effect on the local vasculature, causing vasodilatation and increasing permeability. Tryptase, is an important chemoattractant for neutrophils.
Second, the mast cell will commence synthesis of the lipid derived mediators prostaglandins, leukotrienes and throm- boxanes. The function of these molecules, derived from metabolism of arachidonic acid by cyclooxygenase and lipoxygenase enzymes, overlaps those of histamine and tryptase, resulting in vasodilation.
After a few hours, the mast cell will start to release cytokines. Tumour necrosis factor TNF is a critical chemoattractant for neutrophils. Other cytokines include IL-4, IL-5, IL-6, IL-13.
203
How are circulating informed of bacterial invasion?
Neutrophils in circulation are informed about sites of infection by chemoattractrant molecules.
- Complement anaphylotoxins (C3a, C2b, C4a and C5a),
- Tryptase, TNF, prostaglandin PD2 and leukotriene LTB4 (derived from mast cells)
- Interleukin-1 (derived from keratinocytes and macrophages)
- Chemokines including interleukin-8 (derived from keratinocytes and leucocytes)
204
The immune system achieves it by using a complex system of adhesion molecules and chemoattractants that stop the neutrophils from circulating and allow them to leave the blood vessels - how is this accomplished?
- Rolling is mediated by the presence of P- and E-selectins on endothelial cells of blood vessels.
- Once slowed, the neutrophils are arrested by the interaction between Intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) which upregulated on endothelium following activation by IL-1 and TNF.
- Diapedesis is modulated by interactions between ICAM-1 and a receptor known as macrophage antigen-1 (MAC-1).
- The neutrophil’s through endothelial cells, known as paracellular migration, is controlled by multiple adhesion molecules including ICAMs and platelet/endothelial-cell adhesion molecule 1 (PECAM1)
205
P-selectin glycoprotein ligand 1 (on neutrophils) requires the addition of what key recognition determinant order to become functional?
sialyl Lewis X tetrasaccharide (sLex)
206
Once neutrophils reach the basement membrane and pericyte sheath, the neutrophil uses what two enzymes in order to create a hole to reach the dermis?
Matrix metalloproteinases (MMPs) and neutrophil elastase
207
Once neutrophils are in the dermis, the pro-inflammatory cytokines IL-1a, IL-1b, TNF and IL-6 induce the expression of what neutrophil attracting chemokines? Once there, the army of neutrophils will start to amass, resulting in the accumulation of cells we refer to as pus.
CXCL1
CXCL2 (also known as Macrophage inhibitory protein 2), CXCL5 (also known as epithelial cell-derived neutrophil-activating peptide
CXCL8 (also known as IL- 8)
208
Monocytes leaving the bloodstream are referred to as ________ when they enter sites of inflammation within tissues.
macrophages
209
What are the three distinct activation pathways that can result in different functions for macrophages?
1) The classic pathway of activation involves− interferon-IFN and TNF. These “Type 1” activated macrophages produce IL-12 and are primed for phagocytosis.
2) Macrophages can also be activated via their Fcy receptors, resulting in a Type 2 phenotype which produces IL-10 and has an anti-inflammatory function.
3) Or produces IL-4 which results in an “alternative” macrophage which contributes to wound healing
210
Activation of TLRs has what effect(s) on neutrophil function?
1) including enhancement of phagocytosis
2) production of IL-8
3) shedding of L-selectin
4) reduction of chemotaxis
211
Bacteria that are opsonized by complement proteins or immunoglobulins are primed for phagocytosis. Neutrophils express which complement and immunoglobulin receptors?
Neutrophils express the complement receptors ClqR, CD35, CD11b/CD18 (CR3), and CD11c/CD18 (CR4), and
immunoglobulin receptors FcyR1, FcyR2, FcyR3 (to detect IgG) and FcaR (to detect IgA)
212
A strong oxidative burst is initiated in the phagosome by _____-dependent oxidases upon triggering of specific cell surface receptors, leading to the generation of highly toxic reactive oxygen species (ROS) such as O2−, H2O2, and HClO−. These molecules are similar to household cleaning products such as hydrogen peroxide and bleach and were originally thought to provide the major killing activity in neutrophil phagosomes.
NADPH
213
Neutrophil granules contain which enzymes that contribute to bacterial killing?
Lysozyme, elastase, cathepsin G, azurocidin, proteinase-3, acid hydrolases and gelatinase
214
Lysozyme is now known to split the ______ between N-acetylmuramic acid and N-acetylglucosamine in the cell walls (peptidoglycan layers) of Gram-positive bacteria
b-linkages
215
Neutrophil granules contain factors that sequester essential nutrients to inhibit bacterial growth and survival, such as _________, which sequesters iron and copper; _______, which binds to and sequesters vitamin B12, ________, which binds to bacterial siderophores and prevents the bacteria from extracting iron.
Lactoferrin
Transcobalamin I
Neutrophil gelatinase associated lipocalin,
216
If S. aureus bacteria enter the cytoplasm of neutrophils they encounter a protein complex called ________, which inhibits S. aureus growth through chelation of Mn2+ and Zn2+
calprotectin (S100A8/S100A9)
217
Neutrophils have been shown to cast out their DNA in response to infectious stimuli. This network of extruded chromatin, to which is attached proteins from the neutrophil’s granules, is known as what?
a neutrophil extracellular trap (NET) and is thought to be a central part of antimicrobial innate immunity.
This cell death process is distinct from apoptosis and necrosis and depends on the generation of reactive oxygen species (ROS) by NADPH oxidase.
***Staphylococci can secrete endonucleases that can liberate them from these traps..aureus can also produce two enzymes, nuclease and adenosine synthase, that can convert NETs to deoxyadenosine. This process also triggers the caspase- 3–mediated death of immune cells, resulting in the exclusion of macrophages from staphylococcal abscesses
218
Staphylococci can inhibit neutrophil recruitment to sites of infection by secreting various molecules such as _____ and _____. These proteins block the interaction between P-selectin glycoprotein ligand 1 on the neutrophil surface and P-selectin on the endothe- lial lining, thereby blocking neutrophil rolling
staphylococcal superantigen-like protein-5 and protein-11
219
What protein produced by Staph can inhibit the binding between ICAM-1 and Mac-1 or LFA-1, thus affecting firm adhesion?
extracellular adherence protein
220
What is a predominantly cell bound protein produced by Staph (also be found in the supernatant) that can bind the Fc and Fab regions of immunoglobulin G and inhibit the antibody’s ability to opsonise the bacteria?
Protein A
221
S. aureus can also secrete what enzyme that can convert plasminogen into plasmin. Plasmin can cleave IgG and C3b that is bound to the bacteria’s surface, again inhibiting opsonisation?
Staphylokinase
222
Staphylococci secrete what molecules that can interfere with the complement cascade?
Staphylococcal complement inhibitor SCIN
Extracellular complement-binding protein Ecb
Staphylococcal superantigen-like protein SSL7
These proteins can interfere with convertase enzymes, preventing development of the complement components and, again, inhibiting opsonisa- tion.
223
Even if S. aureus fails in its bid to avoid opsonisation and it gets phagocytosed, it has strategies to facilitate survival within the neu- trophil. The bacteria can produce which two toxins that lyse the neutrophil from within?
phenol-soluble modulins and leukocidin AB
This process, known as programmed necrosis, involves acti- vation of specific receptors that divert the neutrophil away from an apoptotic pathway and prevents its removal by macrophages
224
Once T cells are activated activated, clones of helper T cells can rapidly deploy to the skin. These cells express the cutaneous lymphocyte antigen (CLA), a member of the sialy Lewis-X glycoprotein family. The ligand for CLA is likely to be ______, the adhesion molecule mentioned earlier that is critical for neutrophil trafficking
E selectin
225
TH1 cells promoting ______ activation, and TH2 cells promoting ______ and IgE antibody responses.
macrophage
| B cell activation
226
TH1 lymphocytes produce which cytokines and their functions?
L-2 (promotes T cell proliferation)
| IFN (activates macrophages and promotes TH1 responses) TNF (activates macrophages)
227
TH2 lymphocytes produce which cytokines and their functions?
IL-3 (stimulates haematopoiesis and mast cell differentiation)
IL-4 (promotes TH2 differentiation and IgE formation)
IL-5 (promotes eosinophil development and survival)
IL-13 (promotes B cell proliferation and IgE production)
IL-14 (promotes B cell differentiation)
228
Which cytokine in the defence against S. aureus as it stimulates neutrophil recruitment to the site of infection and promotes abscess formation?
IL-17
229
Which cytokine receptors are abundantly expressed on keratinocytes, and activation results in production of defensins and cathelicidin to aid with bacterial killing?
IL-17
230
What are the three major effects Antibodies have in the fight against staphylococcal infections?
1) Act as neutralising antibodies, binding to the pathogen to prevent its attachment to host target surfaces, such as epithelial layers or the extracellular matrix. They also block the binding of toxins and other virulence factors and neutralise their harmful effects.
2) Act as opsonizing antibodies, coating the organism to allow its detection by Fc receptors on phagocytic cells.
3) Bind to pathogens and activate the classical complement pathway.
231
What is the difference between convention antigens and superantigens?
Unlike conventional antigens, which are processed by antigen presenting cells and presented to specific T cell receptors via MHC 2 molecules, superantigens can bypass this entire process.
These molecules are able to cross-link the MHC molecule and TCR directly, without involving the highly specific interaction that take place between the MHC groove and TCR binding site. The end result is that large populations of T lymphocytes are activated in a non-specific manner. The activated T lymphocytes cause a cytokine storm = TSS
232
Define Major Basic Protein
Smallest protein, but very abundant, can generate superoxides and trigger degranulation of neutrophils.
233
Define Eosinophilic Cationic Protein
This protein has weak ribonuclease activity, potent neurotoxicity, induces histamine release from mast cells, and is detected in basophils, neutrophils and monocytes.
234
Define Eosinophil-derived Neurotoxin
Matrix protein of the granules with potent ribonuclease activity, neurotoxic, weak/poor effect on helminthes, also detected in neutrophils and basophils.
235
Define Eosinophil Peroxidase
Matrix protein of the granules, most specific for eosinophils, less abundant than other proteins, but highest molecular weight.
236
Langerhans cells are anchored to keratinocytes in the epidermis via?
E-cadherin
237
VCAM is part of which immunoglobulin family?
immunoglobulin super-family
238
What inflammatory mediator plays an important role in stimulating emigration of LC; function in both the loss and replacement of LCs in the epidermis
TNF-α
239
What chemokine is essential for LC migration to skin draining LNs?
CCR7 (CC-chemokine receptor 7)
240
What is the effect of UVB on LC cells?
UVB decreases antigen presenting capability, reduced IL-1 and IL-6 expression by keratinocytes and decreases overall LC numbers – thereby decreasing immune surveillance
241
What protein reduces the binding ability of gram-negative and gram-positive bacteria?
Transferrin
242
What inflammatory cell are defensins found in?
neutrophils
243
What are two important roles of C3b in the complement pathway?
C3b can opsonize bacteria and promote phagocytosis
| C3b can also activate the MAC
244
In the lectin pathway, what complement protein is activated in the absence of antibodies?
C1
245
What receptors bind gluten in cell walls to facilitate phagocytosis?
Dectin
246
Mast cell derived TNFa and TGFb Kazan promote fibroblast proliferation, and mast cell extracts can activate fibroblasts, promoting collagen synthesis and what enzyme involved ion matrix remodeling?
gelatinase A
247
What is it called with auto reactive cells are prevented from reaching peripheral circulation (via apoptosis)?
central tolerance via clonal deletion
248
Autoreactive lymphocytes can be controlled by regulatory T cells ___ and ____ (immunosuppressive cytokines).
IL-10 and TGFb
249
B cells may be activated following direct contact with antigens. ___ and ___ immunoglobulins on the surface of B cells can recognize antigens in this way and stimulate proliferation of the cell and further antibody production.
IgM and IgD
250
What B cells are pre-programmed to produce IgM against common bacterial polysaccharides and lipids. These can product antibody without needing any help from T cells.
B-1 cells
