principles immunology Flashcards
(124 cards)
1
Q
what are 3 barriers to infection
A
skin
mucous
commensal bacteria
2
Q
how does the skin protect against infection
A
physical barrier tightly packed, highly keratinised undergo constant renewal and replacement low pH and low oxygen sebaceous glands - secrete hydrophobic oils, lysozyme, defensins, ammonia
3
Q
how does mucous protect against infection
A
traps invading organisms
contains secretory IgA, enzymes such as lysozyme, defensins, antimicrobial peptides which directly kill pathogens, lactoferrin which starves bacteria of iron
cilia remove mucous
4
Q
how does commensal bacteria protect against infection
A
compete with pathogens for scarce resources
5
Q
what can the use of broad spectrum antibiotics cause
oral
IV
A
oral - oral/vaginal candidiasis
IV - c diff
6
Q
what does the adaptive immune response involve and what is it
A
B cells
antibodies
T cells
dendritic cells
slow response, responsible for immunological memory
7
Q
Neutrophils, monocytes, macrophages and dendritic cells are all…
A
phagocytes
8
Q
phagocytes are an important source of …
A
cytokines
9
Q
B cells, T cells and NK cells are all …
A
lymphocytes
10
Q
eosinophils, mast cells and basophils are all …
A
granular cells - release chemicals for acute inflammation
11
Q
give 2 factors associated with humoral immunity
A
antibodies
complement proteins
12
Q
where do mast cells reside and what do they do
A
reside in tissues and protect mucosal surfaces
13
Q
where are basophils and eosinophils located
A
circulate in blood and are recruited to sites of infection
14
Q
what do basophils, eosinophils and mast cells do upon activation
A
release histamine, heparin, tryptase and pro-inflammatory cytokines
15
Q
what are basophils, eosinophils and mast cells involved in primarily
A
defence against large anti-body coated pathogens that can’t be phagocytosed e.g. parasitic worms
16
Q
if a cell is multinucleate it is a …
A
neutrophil
17
Q
where are neutrophils found
A
circulate freely in blood and are rapidly recruited to inflamed and infected tissue
18
Q
what are 3 mechanisms by which neutrophils attack pathogens
A
phagocytosis
degranulation - release of antimicrobial peptides and degradative proteases
generate extracellular traps
19
Q
what do active neutrophils release
A
TNF (pro-inflammatory cytokine)
20
Q
neutrophils are numerous and short lived
true/false
A
true
21
Q
neutrophils make use of PAMP recognition and activation
true
A
true
22
Q
what makes up pus
A
dead and dying neutrophils + tissue cells + microbial debris
23
Q
what cells are precursors of macrophages
A
monocytes
24
Q
where are macrophages found
A
reside in tissues
25
what do macrophages do when active
ingest and kill extracellular pathogens
26
what do macrophages do when neutral
clear debris from tissue cells
27
give 3 other functions of macrophages
inflammation
tissue repair and wound healing
antigen presentation
28
how are macrophages attracted to apoptotic cells
apoptotic cells release an 'eat-me' signal
29
what are the 4 stages of phagocytosis
| apoptotic cell
1) formation of a phagocytic cup around cell
2) pinches off forming a phagosome
3) fusion with lysozyme forms a phagolysosyme - degradation of contents
4) debris released into ECF
30
what is released along with cellular debris from a phagocyte
anti-inflammatory mediators e.g. IL10
31
what are the 5 stages of phagocytosis of a pathogen
1) phagocytic cup around pathogen
2) pro inflammatory stimuli released e.g. LPS, INF-Y
3) this enhances macrophage activation and the production of toxic NOS and RNS
4) pinches off forming phagosome
5) antigen presentation --> activated macrophage
32
give 3 infections which evade phagosomal killing
salmonella
staph aureus
mycobacteria
33
where are dendritic cells found
immature cells in peripheral tissues / tissues with contact to external environment
34
what do dendritic cells do when they come into contact with a pathogen
mature and migrate to secondary lymphoid tissues
| stimulate adaptive immune response through antigen presentation
35
how do dendritic cells become activated
phagocytose, process and present antigen on surface to T cells
36
what do NK cells release
pro-inflammatory mediators e.g. IFN-Y
37
what kind of cells are NK cells
large granular lymphocytes
38
what do NK cells kill
tumour and virally infected cells - don't express MHC class 1 which is present in normal cells to inhibit NK action
can also kill antibody-bound dresses
39
what do B cells do
```
produce antibodies (humeral immune response)
which coat pathogens to help phagocytosis
```
40
what are the 2 types of T cells
helper T cells
| cytotoxic T cells
41
what do helper T cells release
CD4+
most people need HELP for T4
42
what do cytotoxic T cells release
CD8+
43
what do helper T cells do
activate other immune cells - receptor:ligand interactions
| produce cytokines that help phagocytes kill ingested bacteria
44
what do cytotoxic T cells do
kill virally infected body cells
45
what is primary lymphoid tissue
site of leukocyte development
red Bone marrow and Thymus
(B for B cells) (T for T cells)
46
what is the function of lymph nodes
positioned regularly along lymph vessels - trap pathogens and antigens in lymph
47
how does lymph move
valves and muscle movement
48
what is secondary lymphoid tissue
sites where adaptive immune response is initiated (lymph nodes - tissue infections, tonsils, spleen-blood borne infections)
49
what are cytokines
produced in response to infection, inflammation and tissue damage
they co-ordinate the immune system by modulating cell behaviour
indirect communication
50
what are 4 examples of cytokines
interferons
TNF
chemokines
interleukins
51
what kind of cells produce and release interferons and what is their function
virally infected cells
signals neighbouring cells to destroy RNA and reduce protein synthesis and to undergo apoptosis
activates immune cells e.g. NK cells
52
what is the function of IL2 and what is the source
T cell proliferation
| Th1 cells
53
what is the function of IL10 and what is the source
anti-inflammatory - inhibits Th1 cytokine production
| Th2 cells
54
what are some s/s of acute inflammation
```
redness
heat
swelling
pain
loss of function
fever
```
55
what does the innate immune response involve and what is it
```
mast cells
NK cells
phagocytes
complement
neutrophils
macrophages
```
rapid, general response responsible for acute inflammation and killing of pathogen
56
what are the 3 phases of the innate immune response
recognition phase (PRRs:PAMPs)
activation phase
effector phase
57
PAMPs are specific to certain pathogens
| true/false
false
| there is a limited number of PAMPs which are common to many different pathogens
58
what are the 2 forms of communication in the immune system and give an example of each
1) direct - receptor:ligand
MHC:TCR
PAMP:PRR
2)indirect - production and secretion of cytokines
ILs, interferons, TNF
59
what drives the acute phase response
cytokines
60
what organ produces acute phase proteins in response to pro-inflammatory cytokines (IL1, IL6, TNF)
liver
61
what are 3 examples of acute phase proteins
CRP
complement proteins (C3, C4, mannose-binding lectin)
Serum amyloid A
62
what is the complement system
family of proteins produced in the liver that circulate in blood and enter inflamed and infected tissues where they become activated
63
what are the 3 pathways of complement system activation
classical
mannose binding lectin
alternative
64
when triggered specific complement proteins can enzymatically activate other complement proteins in cascade
true/false
true
65
what is the complement equation
C3 ---> C3b + C3a
66
what do C3b + C3a do
activation of downstream complement proteins
67
what does the activation of downstream complement proteins cause
pathogen killing (MAC)
pathogen opsonisation
leukocyte recruitment and inflammation (chemotaxis)
removal of immune complexes
68
how is the mannose-binding lectin pathway stimulated
mannose expression unique to certain microorganisms (not expressed on human cells)
69
how is the alternative pathway stimulated
spontaneous breakdown of C3
| C3b is stabilised on bacterium but degraded on human cells
70
how are C5a and C5a formed
C3b causes C5 ---> C5a and C5b
71
what complement proteins are involved in leukocyte recruitment and inflammation
what do they do?
C3a and C5a
act directly on BVs to increase permeability and therefore increase leakage from blood
activate mast cells/basophils which release pro inflammatory mediators e.g. histamine and chemokines
72
how is the MAC formed
C5b binds to surface of pathogen
| C6 7 8 and 9 assemble with C5b forming MAC
73
how does the MAC work
inserts into target cell walls - osmotic cell lysis of pathogen
74
what is pathogen opsonisation
coating of pathogen by humoral factors (opsonins) to facilitate phagocytosis
phagocytes express receptors for opsonins on cell surface
75
what are 4 examples of opsonins
C3b
CRP
IgG
IgM
76
complement proteins have a short half life
| true/false
true
77
only cleaved complement proteins are active
| true/false
true
78
what traps opsonised cells in B cell zones
stromal cells
79
how do T cells recognise a pathogen
T cell antigen receptor
- membrane bound protein heterodimer
- has alpha and beta chain
80
how do B cells recognise a pathogen
B cell antigen receptor
- membrane bound antibody (IgM or IgD)
- has a light and heavy chain and disulphide bridges
81
how do lymphocytes find the pathogen
secondary lymphoid tissue
82
lymphocytes require 2 signals to be activated
| true/false
true
83
how are T cells activated
MHC/HLA proteins display peptide antigens to T cells
84
what class of MHC/HLA present peptide antigens to cytotoxic T cells (CD8+)
```
class I
expressed on all nucleated cells
```
85
what class of MHC/HLA present peptide antigens to helper T cells (CD4+)
```
class II
expressed only on dendritic cells, macrophages, B cells
```
86
do B cells need dendritic cells to recognise antigens
no - do not need antigen to be presented by MHC
87
what is the name for the immunoglobulins that are produced by B cells in response to an antigen that bind specifically to a single epitope
antibodies
88
what do antibodies provide defence against
extracellular pathogens - bacteria, viruses, toxins
89
how do the 5 types of antibody differ
different Ig heavy chain constant region
90
how are the 2 heavy and the 2 light polypeptide chains held together
disulphide bonds
91
what is the most abundant Ig
IgG
| G for global
92
how does IgG cross the placenta
active transport
93
what is the 1st Ig produced during an immune response
IgM
| IMmediately
94
what Ig is produced in the allergic response
IgE
95
what Ig is the 2nd most abundant and found in mucosal secretions
IgA
96
what form is IgA in secretions
dimer
97
what form is IgA in the blood
monomer
98
what Ig can form a pentamer
IgM
too big to pass to foetal circulation
M has 5 points on it
99
what region of the Ig is responsible for recognition function
variable region
100
what region of the Ig is responsible for effector function
constant region
101
where does IgE bind
Fc receptor
102
give 5 functions of antibodies
agglutination - immune complex formation - aids phagocytosis (IgM and IgG)
opsonins (IgG)
stimulate NK cells (antibody dependent cell mediated cytotoxicity - ADCC) - IgG
trigger allergic reactions
undergo class switching ( switch heavy chain segment) - induced by specific cytokines
103
what can B cells differentiate into
plasma cells - effector B cells which produce antibodies
| Memory B cells - immunological memory
104
what is the Germinal centre reaction
B cell proliferation
antibody heavy chain switching
generation of high affinity antibodies
differentiation into plasma cells and memory B cells
105
how do naive B and T cells enter lymph nodes from high endothelial venules
transendothelial migration
| - after several days if they don't encounter specific antigen they return to blood via the efferent lymphatics
106
what is a major source of IL2
helper T cells
107
what immune cells mediate acute and chronic organ rejection
helper T cells and cytotoxic T cells
108
what immune cells mediate hyperacute organ rejection
B cells
109
what is the most common WBC
neutrophils
110
what is the main immune cell against protozoan and helminth infections
eosinophil
also IgE
E
111
what shape nucleus do monocytes have
kidney
112
what cell is a source of IL1 and TNF alpha
macrophage
113
Basophils and Mast cells express what receptors on their surface
IgE receptors (Fc)
114
what cells release histamine during an allergic reaction
mast cells
115
what kind of molecule is IgG
monomer
116
what is the most commonly produced Ig
IgA
| but conc. lower than IgG which is most common
117
what Ig mediates hypersensitivity reactions
IgE
118
what is the least abundant Ig
IgE
119
what does HIV use to enter a cell
CD4
120
what is the co-receptor for MHC class II
CD4
121
what is the co-receptor for MHC class I
CD8
122
what is the function of TNF alpha/IL1
induces fever, neutrophil chemotaxis
123
what is the function of INF gamma
activates macrophages
124
what is a source of INF gamma
Th1 cells
