Adaptive Immune System

Question 1

Definitions

Answer 1

Mature lymphocyte: has undergone antigen-independent development in primary lymphoid organs and has entered circulation (recirculates)

• Naive lymphocyte: mature lymphocyte that has not been exposed to cognate antigen in periphery.
• effector lymphocyte: differentiation state that relates to specific function in the immune response: depends on Ag-specific activation.
• memory lymphocyte: Ag-activated lymphocyte that has not differentiated sufficiently to become and effector lymphocyte.
• epitope/antigenic determinants: the parts of the antigen that the antibody binds to.
• Hapten: small foreign molecules that antibodies bind to but on its own are not immunogenicity enough to stimulate an immune response. The Hapten must be linked to a conjugate (carrier polypeptide).

Question 2

Key features of the adaptive immune system

Answer 2

1. Diversity: many different B/T cells specific only for one antigen each (many different idiotypes).
2. Specificity: the clones produced are specific for the original antigen many clonal B/T cells specific for the same antigen. Increase in affinity due to differentiation.
3. Recognition of non-self: no B/T cells for self-antigens (tolerance).
4. Memory: greater number of cells specific for an antigen remain (better chance of recognising antigen on subsequent encounter).

Question 3

What are the primary lymphoid organs and what occurs in them?

Answer 3

-bone marrow and thymus (and foetal liver and spleen)
- antigen- independent development (production).
It has four steps:
1. Micro environment for lymphocyte development (cytokines and stromal components)
2. Antigen receptor rearrangement
3. Editing (positive and negative selection)
4. Release of naive mature lymphocytes into circulation.

Question 4

What are the secondary lymphoid organs and what occurs in them?

Answer 4

• GALT (tonsils, adenoids, appendix, Peyer’s patches, MALT, lymph nodes and spleen.
• antigen-dependant development (proliferation and differentiation).

Question 5

Lymphoid lineage

Answer 5

T cells
B cells
Natural killer cells
Dendritic cells: neutrophils, eiosinophils, basophils, macrophages

Question 6

Myeloid lineage

Answer 6

RBCs, megakaryocytes, mast cells, tissue macrophages, immature dendritic cells.

Question 7

TCR Diversity

Answer 7

T cell diversity is achieved by the rearrangement and expression of TCR genes.
TCR chain loci (alpha and beta chains) are located on separate chromosomes. Beta chain locus: V, D and J
Alpha: V and J.
You can make 10 to the power of 10 possible combinations.