Adaptive Immunity I Flashcards
1
Q
Describe the purpose of the innate immune system
A
- first line of defence- fast, nonspecific
- humoral and cell mediated
- activated within mins
- buying time for adaptive immune system to kick it
2
Q
What do Primitive T cells do?
A
- recognise antigens similarly to the innate immune system
3
Q
Describe the role of the adaptive immune system
A
- humoral and cell mediated (using B an T cells)
- slower to develop (5-6 days)
4
Q
Which recognition molecules does the innate immune response use?
A
- germ line encoded pattern recognition receptors
- these bind to pathogen - and damage-associated molecular patters- generic molecules found on many different types of pathogen (e.g. LPS) or released in response to stess/ tissue damage
5
Q
Which recognition receptors does the adaptive immune system use?
A
- randomly generated B and T cell receptors
- highly specific to individual antigen molecules, rather than generic molecules found on many pathogens
6
Q
What cell produces antibodies?
A
- B cells
7
Q
How can antibodies provide passive immunity?
A
- transferred between individuals
8
Q
What is the difference between humoral immunity and cell-mediated immunity?
A
- humoral - antibodies
- cell mediated - involved primarily T cells
- these eradicate pathogens, clear infected self-cells, or aif other cells in inducing immunity
9
Q
Fill in the gaps and describe the process
A
- only naive cells should be released into circulation
- continually circulate through body
- go into secondary lymphoid organs looking for their specific antigen
- if it encounters its antigen - clonally proliferates so more effective
- these cells will eliminate pathogen
- effector cells die
- left with memory cells
10
Q
How do the innate and adaptive immune systems work together?
A
- dendritic cell key - initiates adaptive IS
- need the innate immune cells to sense the danger and to become APCs
- helper cells then produce cytokines that can help B cells and NK to form a better antibody response
11
Q
What is happening here?
A
- primary response initiated upon first exposure to antigen
- memory lymphocytes left behind
- a second exposure to same antigen - stimulates memory cells
- reactivation yields a faster/ more effective reponse
- memory NOT present in innate immunity
12
Q
Why are memory cells more effective?
A
- more of them
- more easily activated
- more effective
- reside in/ home back into the tissue where first infection occured
13
Q
What forms may an antigen be in?
A
- protein, lipid, carb, nucleic acid or any combo of these
- foreign or altered self molecules
- soluble or particulate
- simple or complex
14
Q
What is an antigen?
A
- a processed peptide derived from a foreign or alter self protein and presented by MHC I or II molecules
15
Q
What do CD8/ CD4 T cells recognise peptides presented by?
A
- CD8 - MHC I
- CD4 - MHC II
16
Q
What is the antigen receptor on B cells?
A
- membrane-bound form of IG secreted upon stimulation
17
Q
Membrane bound IG =
Secreted IG =
A
- BCR
- antibody
18
Q
Describe the structure of an antibody
A
- 2 heavy chains
- 2 light chains
- held together by intra/interchain disulfide covalent bonds
19
Q
Label this
A
20
Q
What is the function pf CH1 and CL domains?
A
- extend arms of the antibody away from hinge region
21
Q
What is the function of the VH and VL domains?
A
- variable regions are made of Ig folds
- contain 3 hypervariable loops called CDRs
- produce ability of Ab to bind to its specific antigen
- each Ab can bind to 2 antigens
22
Q
What is the function of the carboxyl-terminal domains?
A
- confers the effector activity of the Ab
- membrane-bound Ab has a hydrophobic tansmembrane segment and very short cytoplasmic tail
- secreted Ab is formed by alternative RNA splicing mechanisms that remove/ replace these regions
23
Q
What is the process of signal transduction in B cells?
A
- BcR has v little cytoplasmic domain and cannot signal
- but complexes with 2 Igalpha and 2 Igbeta chains (CD79a + CD79b)
- Igalpha and Igbeta have signaling motifs in their cytoplasmic chains
- phosphorylation of the ITAMs triggers signaling cascades
- CD19 acts as a co-receptor further initiating the signaling pathways
24
Q
What are TCRs?
A
- T cell receptors
- not Ig
- belong to the Ig superfamily
- possess V and C domains
- CDRs (complementary determining regions) are found on the variable regions of each chain- bind to MHC
- heterodimers (alpha and beta chain)
25
How do T cells signal?
* TCR cannot signal
* transduction is initiated through ITAMs expressed by chains of the CD3 complex
* T cell co-receptors CD4 and CD8 also bind to MHC to aid signal transduction
* CD28 involved
26
How can a limited amount of DNA genetic info produce an extensive variety of antibodies?
* B cells use groups of PARTS of genes to create different possible antibodies using recombination
27
Name the different gene segments used.
* Variable
* diversity
* joining
* constant
28
Which segment is used in antibody heavy chains only?
* D
29
What are the 2 types of light chains?
* kappa
* lambda
30
What happens if you change the heavy constant gene segment?
* change tail of antibody
* change the functional properties
* greater diversity of constant gene segment
31
Describe the mechanism of V(D)J recombination
* recombination is directed by signal sequences (RSSs) flanking each antibody gene segment
* gene segments joinedby the recombo activating gene recombinases RAG1/2
* RAG1 forms a complex with RSSs stabilized by binding RAG2
* +other proteins required
* V(D)J proteins results in functional Ig variable region gene
* RAG proteins bind and cleave the DNA
* other proteins process tha hairpin loops that form after RAG has done its job
* products include a recombines coding joint and a leftover signal joint that is later degraded
32
What are the 4 mechanisms that generate antibody diversity in naive B cells?
1. Multiple gene segments
2. nucleotides can be inserted between joints
3. exonuclease trimming
4. combinatorial diversity (which heavy chains pair with light chains)
33
What are the 2 receptors that thymocytes can express?
34
Which thymocyte receptor is more common in fetal development and how does this change?
* TCRygamma are more common
* but decrease after birth in mice
* (retained as a major pop in ruminants, pigs and chickens)
35
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