L94: Adaptive Immunity I Flashcards
What are the two components of adaptive immunity?
- Cell-mediated response;
2. Humoral (antibody) response.
Which cells carry out the responses of adaptive immunity?
T and B cells
What is the role of T cells in adaptive immunity?
T-cells drive cell-mediated immunity, this includes activation of macrophages, natural killer cells (NK) and antigen-specific cytotoxic T-lymphoctyes.
What is the role of B cells in adaptive immunity?
B-cells drive the humoral response through the production of antibodies.
What is the main difference between innate and adaptive immunity?
In adaptive immunity, there is an immunological memory.
What is immunological memory?
Where each pathogen is ‘remembered’ by a specific T-cell receptor and/or B-cell receptor.
Describe the kinetics of adaptive immunity:
- ‘Establishment of infection’ occurs as a microorganism has entered and reaches the antigen threshold level to initiate an adaptive immune response (innate immune response happens here too);
- Once threshold has been reached, ‘induction of adaptive response’. At this point the level of microorganism continues to increase;
- Once the ‘adaptive immune response’ has been initiated, the level of microorganism begins to clear;
(area under the graph from 1-3: duration of infection)
- After clearance, ‘immunological memory’ is achieved. (up to 20 years).
With regards to genetics, what is the difference between innate and adaptive immunity?
Innate immunity is regulated by one gene, adaptive is regulated by multiple genes leading to many signature patterns for immunity.
What are the three main molecules involved in recognition of foreign antigens? (adaptive)
- T-cell Receptor (TCR);
- B-cell Receptor (immunoglobulins [Ig]);
- Major histocompatibility complex (MHC proteins).
What are the two classes of T-cells?
- CD4+ (helper);
- CD8+ (cytotoxic).
What does CD stand for?
Cluster of differentiation (cell surface markers involved in signalling)
What does MHC stand for?
Major histocompatability complex (cell surface markers involved in signalling)
Which MHCs do CD4+ cells interact with?
MHC Class II
Which MHCs do CD8+ cells interact with?
MHC Class I
What is CD3?
A co-receptor involved in the binding and activation of both CD4 and CD8 (also co-receptors) to MHCs
Describe the structures of T-cell receptors (TCR):
- Two classes of TCRs: ab chains and gd chains (antigen binding sites);
- Majority are ab;
- Each chain, a and b (or g and d) have a variable and a constant region;
- For an a-chain, two gene segments encode the variable region of the chain;
- V (variable) and J (joining);
- For b-chains, three gene segments encode for the variable region of the chain;
- V (variable), D (diversity) and J (joining);
- This leads to millions of T-cells, each specific to one antigen.
What process (genetic) leads to variation within TCRs?
Somatic recombination (mutation)
Which part of the TCR is specific to different antigens?
The antigen binding site
In the body, where are B and T cells produced?
The bone marrow
In the bone marrow, lymphocytes are…
Undifferentiated
Where are B-cells processed (differentiated)?
The bone marrow
After differentiation of lymphocytes to B-cells, where are B-cells transported to?
The blood stream and lymphatic organs
Give two examples of lymphatic organs
- Lymph nodes;
- Lymphatic ducts;
- Spleen
Where are T-cells processed (differentiated)?
The thymus gland
