U3 L1 Immunology Recap Flashcards
1
Q
What is the innate humoral response?
A
Complement
2
Q
What cells are involved in the innate cellular response?
A
NK cells, macrophages, monocytes, neutrophils, mast cells
3
Q
What is the adaptive humoral response?
A
Antibody involvement
4
Q
What is the adaptive cellular response?
A
Involvement of B cells and T cells
5
Q
What are the 1st, 2nd and 3rd lines of defence?
A
1st - physical and chemical barriers
2nd - innate
3rd - adaptive
6
Q
What are the characteristics of innate response?
A
- Rapid
- Same response with repeated exposure
- Exists at birth
- Non-specific and indiscriminate
- No immune memory
7
Q
What are the characteristics of adaptive response?
A
- Specific to epitope or antigen
- Immune memory
- Distinguishes between self and non-self
- Relies on mechanisms that develop as result of infection (slow)
8
Q
What are the functions of a macrophage?
A
- Secretion of enzymes, cytokines to modulate immune response
- Phagocytosis
- Antigen processing and presentation to T helper cells via MHC Class II
9
Q
What are the types of macrophage?
A
- Alveolar - in lungs, phagocytosis
- Kuppfer - in liver, initiate immune response
- Microglia - in brain, immune surveillance and phagocytosis
- Splenic - in spleen, elimination of old/damaged RBC
10
Q
What is the process of phagocytosis?
A
- Chemotaxis
- Adherence of microbe to macrophage
- Ingestion of microbe
- Phagosome formation
- Formation of phagolysosome
- Digestion by enzymes
- Formation of residual body
- Discharge of waste materials
11
Q
What is chemotaxis?
A
Movement of phagocyte towards site of infection e.g. due to release of factors by bacteria
12
Q
How do microorganisms adhere to a phagocytic cell surface?
A
Adherence to receptors eg.
- lectin receptors
- complement (C3b) receptors
- Fc receptors
13
Q
How is the microorganism injested by the phagocytosing cell?
A
- adherence to receptors causes cytokine-skeletal activation of phagocyte
- activation of actin-myosin contractile network to extend pseudopodia around microorganism
14
Q
What is the pH of a phagosome?
A
PH 7
15
Q
What sort of pH is present in a phagolysosome?
A
Acidic
16
Q
Why is pH in a phagolysosome low?
A
Stimulate activity of agents e.g. reactive oxygen species, proteases, lysozymes to break down the microorganism
17
Q
What is the function of reactive oxygen species, hydrogen peroxide, hydroxyl radicals in a phagolysosome?
A
Oxidise microbial membranes causing destruction
18
Q
What is the function of lysozyme?
A
Destruction of bacterial membranes
19
Q
What cells are considered granulocytes?
A
- Neutrophils
- Eosinophils
- Basophils
- Mast cells
20
Q
What are neutrophils involved in?
A
- Acute inflammation
- Phagocytosis
- Killing of bacteria by oxidative mechanisms
21
Q
What kinds of factors do neutrophils release?
A
Kinins, chemotactic factors (e.g. IL-8), pyrogens, bacteriostatic proteins
22
Q
What is the most abundant leukocyte?
A
Neutrophil
23
Q
What are eosinophils involved in?
A
- Allergic reactions
- Parasite immunity (not phagocytosed)
- Some inflammatory conditions
24
Q
What is respiratory burst?
What cells undergo respiratory burst?
A
Generation of reactive oxygen species
Macrophages, neutrophils, eosinophils
25
What chemotactic factors attract eosinophils towards the site of infection?
What receptors do eosinophils have?
IL-5, C3a
Fc and C3b receptors
26
How are basophils and mast cells linked?
Basophils travel from blood into tissue where they become mast cells
27
What kinds of antibodies do mast cells bind on their surface?
IgE via Fc receptors
28
What causes degranulation of mast cells?
Binding of antigen (Ag) to IgE; causes IgE cross links in membrane
29
What preformed molecules do mast cell granules contain?
- histamine
- proteases
- chemotactic factors for neutrophils, eosinophils
- pro-inflammatory cytokines
30
What is a lymphocyte?
White blood cell
31
What is the function of a natural killer cell?
To destroy tumour cells or host cells infected with a virus
32
How do NK cells recognise tumour or virally infected cells?
Tumour or virally infected cells have modified glycoproteins o surface which NK cell recognises
33
What follows the activation of NK cells after interaction with modified glycoproteins?
Extracellular granule release containing:
- perforin (membrane permeabilising protein)
- TNF
- proteases
34
What are the three functions of the complement system?
1. Opsonisation of microorganisms for phagocytosis
2. Activation of leukocytes in immune defence
3. Lysis of target cells via MAC
35
How is the adaptive response specific?
- antibodies and B cells
- T cell receptors and T cells
36
How are B cells activated?
1. Naive B cell internalises antigen bound to BCR
2. antigen fragments presented on MHC class II on B cell surface
3. Th cells recognise antigens
4. T cell-B cell interaction; CD40 binds to CD40 (ligands), Th secrete cytokines
37
What are antigens?
Proteins, polypeptides released from damaged cells (e.g. virally infected) or
Resident proteins on foreign cell surface
38
What is a B cell epitope or antigenic determinant?
Specific linear peptide sequence or pattern of amino acid residues recognised by given antibody
39
What is a conformational epitope?
Folding of polypeptide brings amino acids together and forms epitope
40
What is a linear epitope?
Series of adjacent amino acids in chain recognisable by antigen
41
Why is a protein considered increasingly immunogenic with size?
More epitopes on surface
42
What are haptens?
Low molecular molecules that bind covalently to proteins which will elicit an immune response
(Antibodies can respond to haptens)
43
What is IgG?
Monomer - classic antibody structure, binds to Fc receptors
Placental transfer
Fixes complement
Involved in opsonisation; enables NK cells to undergo ADCC
44
What determines antibody class?
Fc domain
45
What is ADCC?
Antibody Directed Cell Cytotoxicity
46
What is IgM?
Pentameter - 5 monomers linked
First Ig made by foetus and B cells
B cell antibodies are IgM
Fixes complement
47
What is IgA?
Dimer
Major secretory Ig e.g. mucosal surfaces, tears
Binds to Fc receptors on some cells
48
What is IgE?
Monomer, least common serum Ig
Binds to basophils, mast cells in tissues, eosinophils
Important in allergic rxns
49
What is selective activation of B lymphocytes?
Each B cell has specific IgM, bind to specific antigen
50
What is clonal proliferation of B lymphocytes?
Multiplication of activated B cell clones
51
What occurs after clonal proliferation of B cells?
Some differentiation into plasma cells
Some activated B cells will enter lymphoid tissue, become memory cells
52
What is the function of a plasma cell?
Production and secretion of monoclonal antibodies (mainly IgM) to initiate immune response
Can produce IgG, IgM, IgE, IgA with same epitope if T cells involved
53
What is the function of memory cells?
Respond to same initial antigen upon re-exposure
54
How do B cells meet antigens?
1. Antigen delivered to lymphoid tissue, spleen, nodes
2. B cells circulate from lymphoid tissue in blood and lymph
3. Mutations in memory cells can increase affinity for target antigens
55
What are some effector functions of antibodies?
1. B cell membrane IgM as antigen receptor
2. Plasma cell antibodies neutralise antigens
3. IgG, IgM activate classical complement
4. IgG - opsonisation of foreign surfaces
5. ADCC targeted by IgG
6. IgE triggers mast cell activation
7. IgA mediates mucosal immunity
8. IgG mediates neonatal immunity
56
What are cytokines?
Chemical signals transmitting effector functions in immune response
57
What are CSFs?
What are the main functions of CSFs?
Cytokines - Colony-Stimulating Factors
Activate and cause proliferation of granulocytes, monocytes
58
What cells release CSFs?
T-cells, macrophages, fibroblasts, mast cells, endothelial cells
59
What are TNFs?
Tumour Necrosis Factors - pro-inflammatory
60
What cells release TNF-alpha?
What is TNF-alpha involved in?
T cells, macrophages
Tumour cytotoxicity, phagocytosis activation
61
What cells release TNF-beta?
What is TNF-beta involved in?
T cells
Antiviral activity, activation of phagocytosis
62
What are IFNs?
What cells release IFNalpha?
What cells release IFNbeta?
Interferons
Mostly macrophages
Fibroblasts
63
What are the functions of IFNalpha and IFNbeta?
Antiviral
Increases expression of MHC I
64
What cells secrete INFgamma?
What are the functions of IFNgamma?
T cells
Antiviral, macrophage activation, enhanced MHC I and MHC II
Maturation of Cytotoxic T cells
65
What are interleukins?
Chemicals secreted by one leukocyte to act on another
66
What is the function of IL-1?
What cells secrete IL-1?
Pro-inflammatory
- proliferation of activated B and T cells
- induction of fever
- induction of IL-6
Macrophages, fibroblasts
67
How do T cells mediate specific cellular immune responses?
Each T cell has TCR of single specificity; recognises only specific T cell epitope
68
What follows T cell activation via TCR interaction with specific Ag?
clonal selection and proliferation of T cells
formation of T cell effector and memory cells specific for original Ag
69
T cells will only respond to an antigen that is presented on the surface of host cells in association with
proteins derived from Major Histocompatibility Complex (MHC)
70
MHC also known as
HLA - human leukocyte antigen
71
What is the function of MHCs?
act as 'identity markers' on surface of host cells with which T cells interact
72
What cells present MHC I?
To which cells do these cells present the MHC I with antigenic peptide?
all nucleated cells
cytotoxic T cells (CD8+)
73
MHC I presents a peptide epitope derived from where?
1. intracellular synthesis
2. processing of proteins e.g. foreign viral
74
What is the effector function of cytotoxic T cells, CD8+?
to kill 'altered' host cells
75
What cells express MHC II on their surface?
For which is MHC II expressed?
antigen presenting cells - macrophages, dendritic cells, B cells
T helper cells, CD4+
76
Where is the peptide epitope presented by MHC II derived from?
endocytosis of extracellular proteins which is then processed to generate peptide epitopes
77
What is the effector function of a T helper cell, CD4+?
What do T helper cells upregulate in response to immune stimuli?
to promote humoral and cell mediated response
- promote antibody response to antigens
- promote killing of infected cells by CD8+ and macrophages
MHC II expression
78
Diversity of MHCs is responsible for
- organ rejection after transplantation
- some hypersensitivity reactions
79
What are the subtypes of MHC I?
What are the subtypes of MHC II?
Are all subtypes of the MHCs found on cells carrying MHC I or MHC II?
MHC I A, MHC I B, MHC I C
MHC II DP, MHC II DQ, MHC II DR
Yes
80
There is polymorphic diversity in the subtypes of MHC I A, B, C and MHC II .... what does this mean?
different genentic versions of the same subtype, therefore diversity of binding sites and how they are recognised
81
How many polymorphic forms of MHC II DP will an individual inherit?
one from each parent therefore will have two polymorphic forms (most likely)
82
In total how many subtypes of MHC does each individual express from each parent?
What is the benefit to expressing various subtypes?
6
provides broader repertoire for peptide presentation by individual, therefore recognition of foreign antigens
83
What is the benefit to the polymorphic diversity of each MHC I and II subtype?
limits the damage that a viral mutation could have on population, wider protection
