Innate Immunity: Cellular Mechanisms Flashcards
What are the granulocytes and where are they
Neutrophils, eosinophils and basophils
In blood and can migrate into tissue
__ cells are resident in tissues, particularly at epithelial surfaces and is characterized by the presence of abundant intracellular granules
Mast
NK cell
Circulating
Viral infections and tumor cells
Neutrophils
Killing and removal of bacteria and fungi
Eosinophils
Control infection with multicellular parasites
Basophils and mast cells
Allergy (common debilitating immune disorder)
Sequence of events for granulocyte
Resting. Signalling. Activation. Migration from blood and effector function
Appearance of neutrophils
Polymorphic(multilobed) nucleus and neutral staining granules
Abundant in circulation
6 hour half life in blood and 1-2 days in tissue
Replaced from bone marrow
In good health, _ neutrophils will be seen in tissue
Few
What are the two main types of granules in neutrophils
Primary or azurophilic granules
Secondary of specific granules
Primary/azurophilic granules
First appear during their development in bone marrow
Secondary or specific granules
Appears later
3 times more common in the cytoplasm
What stimuli mobilize the granules in neutrophils
Products of bacterial cell walls, complement proteins, the leukotreine group of lipid mediators and small bioactive peptides called cytokines
N-formulated peptides (FMLP)
Bacterial derived and bind to receptors not he neutrophil surface
The complement product, ___ binds to specific surface receptors on neutrophils
Ic3b
Leukotreines
Products of the lipooxygenase pathway or arachidonate metabolism and some, such as LTB4 have potent stimulators effects on neutrophils
Chemokine CXCL8 (IL-8) and TNF-a (a granulocyte-monocyte csf..gym-csf)
Potent effects on neutrophils
What is in primary/azurophilic granules of neutrophils
Microbicidal things
Myeloperoxidasecathepsin G Proteinase-3 Elastase Lysozyme Defensins Bactericidal.permeability increasing protein (BPI)
What is in secondary/specific granules
Microbicidal things
Cytochrome b558 and other respiratory burst components
Lysozyme
Lactoferin
And migration things
Collagenase
CD1 I b/CD18(CR3)
N formyl methionyl leucylphenylalanine receptor (FMLP-R)
Following activation of what are lipids in the cell membrane concerted de novo into inflammatory mediators that have potent effects on vasculature and on inflammatory cells such as neutrophils
Mast cells, macrophages, granulocytes, and lymphocytes
What are the 3 major classes of lipid mediators, converted from membrane phospholipids by phospholipase A2
Prostagladin D2
Leukotrines
Platelet activating factor
Prostagladin D2 (PGD2)
From cyclooxygenase pathway of arachidonic acid metabolism
Binds receptors on smooth muscle in vascular endothelium leading to vasodilation
-increase blood supple and slows leukocytes passing through tissue allowing them to migrate fromt he blood
PGE2 and PGF2 made my macrophages also inflammatory
Leukotreines
Formed when arachdonic acid is converted through the lipooxygenase pathway
Mast cell synthesis-LTB4, C4, D4, E4
Neutrophil synthesizes LTB4
Cause vasodilation and extravasation of fluid into the tissues
PAF
Produced by mast cells and also has effect of relaxing vascular smooth muscle
NSAIDS
Asprin blocks cyclooxygenase so can control arthritis
Side effect nsaid
Increasing stomach inflammation —fatal hemorrhage
Cox-2 selective for pain and inflammation and spares stomach problems
The lipid mediators are released as a result of ___ reactions and have profound effects on smooth muscle in lung, causing bronchial constriction …manifests as ___
Inflammation
Asthma (tightness in chest, wheezing,
Leukotreines and prostaglandins are made from ___ ____. PAF is made from _____
Arachidonic acid
Lysoglyceryl platelet activating factor
Prostagladin are made through what pathway. Leukotreines are made through what pathway. PAF is made through what pathway
P-cyclooxygenase
L-lipooxygenase
PAF_acetyl transferase
What is a cytokine
Polypeptide released by a cell in order to change the function of the same or another cell. Important chemical messengers
Pleitropy
Cytokine with many different effects
Autocrine
Act on cell that releases it
Paracrine
Act on cells immediately around
Endocrine
Cytokines act like hormones
Chemokine
Natural chemical mediators
Act as chemotactic molecules
Trafficking of cells
CXCr5 and CCR4
Coreceptors used by HIV to get into target cell
CXC
Two cysteine residues separated by any aa
CC
Two cysteine next to each other
CX3C
Two cysteines separated by any 3 aa residue
C
One cysteine
Chemokine receptors
G protein receptors with 7 transmembrane spanning domains
More chemokine than receptors-they are shared
CXCL12
Development of secondary lymphoid organs
MPO
Major microbicidal system
Cathepsin G and related serprocidins, proteinase-3 and elastase
Deadly to a range of gram positive and negative organisms and some candida
Cathespins B D E
Bactericidal
Defensins
Cysteine rich antibacterial and antifungal polypeptides
Three defensins make up 5% of all protein in a neutrophil and act by insertion into pathogen membranes to disrupt ion fluxes. Name them.
HNP1-3
BPI
Toxic ot gram negative bacteria
What’s in secondary granules
Preformed receptors and an assortment of proteins
Cytochrome b558 and its associated proteins
Major bactericidal mechanism
Presynthesized receptors for some molecules capable of activating them (FMLP, complement)
Ok
Collagenase and elastase
Break down fibrous structures int he extracellular matrix , facilitating progress of the neutrophil through the tissues
What activates neutrophils and when are they released
C5a, LTB4, FMLP, CXCL8 (IL8)
At site of inflammation
How does a neutrophil get to tissue
Signal, bind, adhere, cross into tissue
What are the 3 basic steps of neutrophil crossing into tissue
Rolling, adhesion and transmigration (specialized adhesion molecules)
The interface between tissue and blood is formed by ___ cells
Endothelial
Tissue signals are given out by endothelial cells lining the post capillary venues. Why
Flow is at its slowest here
Tissue damage, results in release of mediators from _____
Mast cells, such as histamine
What does histamine do
Dilation of vessels to increase leafiness and reduce rate of blood flow facilitate neutrophil access to site
Rolling /marination
Neutrophils adhere very lightly to endothelium and let go…slowing down.
What molecules are responsible for rolling
Selectins, on endothelium
What effect does CXL8, FMLP, TNFa have on endothelium
Express stronger adhesion molecules…
ICAMS on endothelium
What effect does CXCL1-3,5,6,8 and C5a and FMLP have on neutrophils
Express LFA1
What are the three main families of surface proteins for adhesion
Selectin, integrity, ICAM (intracellular adhesion molecules)
Selectins
P-selectin platelet
E-selectin-endothelium
L-selectin leukocyte
Where is P selectin also found
On activated endothelium
What do P and E selectin bind to
Sialylated carbohydrate residue which is constituitively expressed on circulating immune cells -
for rolling
What do L selectins bind to
Glycoproteins cell adhesion molecule (GlyCAM-1) found on the high endothelial venues of lymph nodes
For homing to lymph nodes
Or a glycoproteins cell adhesion molecule on mucosal endothelium, called MAdCAM-1
GlyCAM-1 and MAdCAM-1 guide leukocytes to particular tissues and have been termed ___
Addressins
P selectin
CD62
On endothelium and platelet
Bind sialyl lewis(CD15) on neutrophils
E selectin
CD62E
On endothelium
Bind sialyl Lewis (CD15s) on neutrophils
L selectin
CD62L
On neutrophils
Binds GlyCAM-1 on peripheral lymph node endothelium and MAdCAM-1 on mucosal endothelium
Integrins
Heterodimer ( a and b chain) on leukocytes
Interact with ICAM
B2 integrins
Adhesion in all leukocytes including lymphocytes
B1 integrins
T and B cell function
Leukocyte function associated antigen-1 (LFA-1)
CD11a/CD18
On neutrophils, lymphocytes and monocytes
Binds ICAM-1 and ICAM-2 on endothelium
Macrophage-1 (Mac-1) and complement receptor-3 (CR3)
CD11b/CD18
On neutrophils, monocytes, and some lymphocytes
Bind ICAM1 on endothelium and iC3b following complement activation
P 150/95, and complement receptor 4 (CR-4)
CD11c/CD18 Tissue macrophages (to a lesser extend neutrophils and monocytes)
Bind to iC3b and C4b
ICAM1 is also the receptor for ___
Rhinovirus
ICAMS are expressed one esting endothelium but are up regulated by inflammatory mediators such as __
TNFa
Note. What else are cd11/CD18 used for
Adhesion that are used during other forms of cell to cell contract such as when antigen presenting cells interact with T cells
Chemotaxis
Direct movement of a cell along a gradient of increasing concentration of the attracting molecule (termed chemoattractant) used by neutrophils
What are the most potent chemotactic agents for neutrophils
C5a, FMLP, CXCL8 and LTB4
Brownian movement
Neutrophils have a constant process of random movement akin to gaseous molecules
What happens a chemotactic factos binds at one pole of the cell, two processes take place. What are they
Granule release, to upregulate receptors for the chemotactic factors at that pole
Neutrophil extends its membrane and cytoplasm into thin, footlike processes known as pseudopodia
Pseudopodia
Rich in microtubles, actin, myosin and actin binding protein
After extending it anchors itself and the remainder of the cytoplasm is drawn up. A new pseudopodia achors itself and the process is repeated
Like a caterpillar
Can neutrophils only phagocytosis one thing at a time
No can ingest more than one bacterium or fungus at a time
What do you get when large numbers of phagocytes are involved in an infective process
Abscess filled with pus (dying neutrophils)
Phagocytosis is ineffective in the absence of __
Opsonins
Common opsonins used by neutrophils
C3b and CRP and antibody (specific immune system giving direction to innnate)
Reverse phagocytosis
Granule contents discharged into external milieu…granule proteins and chromatin combine ot form extracellular fibers that bind gram neg and pos bacteria NET
Neutrophils Extracellular traps (NET
Form of innate response that binds microorganisms, prevents them from spreading and ensures a high local concentration of antimicrobila agents to degrade virulence factors and kill bacteria
What are the two routes that neutrophils use to kill
Oxygen dependent and oxygen independent
Oxygen independent mechanism of neutrophil killing
Lysozyme and cathespins
Oxygen dependent mechanisms of neutrophil killing
Respiratory burst
H202-myeloperoxidase-halide system
What is generated in respiratory burst
Superoxide anion 02-
Hydrogen peroxide h202
Singlet oxygen 102
Hydroxyl radical OH
Genetic abnormality in which neutrophil working is impaired
Recurrent bacterial, fungal infections
Failure to thrive
Organ damage and premature death
Some conditions have no secondary granules…
Lung and skin nfecitons with staph a and candida
Sometimes can’t do respiratory burst
Plus forming organisms and fungi cause prolonged infections of bone skin and lungs
Sometimes common B chain of integrins is not synthesized
LAD
Leukocyte adhesion defiency
Failure of leukocyte adhesion
Repeated infection
Superoxide dismutase
HO2+O2-+H—-> O2+ H2O
Myeloperoxidase
H2O2-+2Cl-+H+——> H2O2+Cl2+OH-
Describe the hydrogen peroxide-myeloperoxidase-halide system
H2O2 is generated by the respiratory burst, MPO from the primary granules and a halide such as Cl combine to give chlorine and hydroxyl ions, both of which are toxic to microorganisms
Eosinophils comprise _% of granulocytes in circulation
3-5
NOTE: this statistic hides the amount of eosinophils in tissue. How many there
Several hundred times more in the tissues, they collect at epithelial surfaces and may survive for several weeks
How identify eosinophils
Staining is a result of granule contents, mainly cationic proteins with affinity for acid aniline dyes such as eosin
Main role of eosinophils
Multicellular parasites
Releases toxic, cationic proteins
Eosinophils in allergic disease
Asthma
What are the two types of eosinophils granules
Specific (95%)
Primary (5%)
Specific granules
Cationic proteins
Major Basic protein (MBP_
Eosinophil cationic protein (ECP, also bactercidal)
Eosinophil neurotoxin
Eosinophil peroxidase-similar to MPO generating toxic metabolites
Primary granule
LTC4, LTD4, LTC4 PAF
Produces changes in airway smooth muscle and vasculature…allergic responses
What are there specific receptors for on eosinophils
C3b/C4b (CR-1), iC3b (CR3), C5a and LTB4
IL3, IL5-development and differentiation
GM-CSF-acts on other cells
What are highly selective in eosinophil recruitment
Eotaxin 1(CCL11) and eotaxin-2 (CCL24)
Il-_ is a sufficient growth factor and essential for eosinophils and may also be produced by them
IL-5
What are the most important factors in neutrophil recruitment and activation
I’ll-5 and eotaxins
What are the two main features of mast cells and basophils
Histamine containing granules
Possession of a high affinity receptor for IgE
Half life of histamine
5 minutes
What is the triple response of histamine
Erythema of skin , arterioles dilate, post capillary venues contract
Increased vascular permeability
Histmine acts directly on local axons to induce more widespread vascular changes distant to the injection site
What does histamine do
Vasodilation
Increase vascular permeability
Smooth muscle contraction in airways
What do the protease enzymes do
Mainly tryptic enzymes (cf. pancreatic trypsin)
Digestion of basement membrane causes increased vascular permeability
Digestion of CT to increase cell migration
Cleavage of C3->C3a
What do proteoglycans do
Mainly heparin in mast cells
Mainly chondroitin sulphate in basophils
Responsible for distinctive blue stain
Anticoagulant activity
What do chemotactic factors do
Eosinophil chemotactic factor for anaphylaxis
Neutrophil chemotactic factos
PAF-synthesized de novo
Vasodilator
LTB-D4-synthesized de novo
Eosinophil activators Neutrophil chemoattractants Platelet activators Vascular permeability increased Bronchoconstrictors
Prostagladins (PGD2)-synthesized de novo
Increase vascular perm
Bronchoconstrictors
Vasodilator
What are the two receptors for histamine
H1 and H2
H1 receptors
Mediate the vascular and bronchial smooth muscle effects and is blocked by drugs such as mepyramine and terfenadine, which form the basis of many proprietary antihistamines used for allergic reactions such as hay fever
H2 receptors
Mediate gastric acid secretion and is blocked by the now famous drugs cimetidine and ranitidine, which treat gastric and duodenal ulceration
Consequence of mast cell and basophils degranulation
Histamine-smooth muscle contraction-airway obstruction tear formation, nasal discharge(coryza), conjunctival redness, gritty eyes and itching
Anaphylaxis-syndrome of circulatory shock and collapse with low blood pressure and chest tightness leading to arrrested breathing and death unless treated
How are mast cells and basophils activated
IgE-both
C3a, C4a and C5a -activate basophils and lung mast cells
FMLP-basophils
