🌞 Adaptive Immunity: Overview and Clonal Selection Flashcards
(11 cards)
What does clonal selection theory propose?
- Multi LC clones (diff specificities)
- Clonal deletion: self-reactive Ls eliminated
- Clonal selection: AG selects specific L clone
-
Clonal expansion + differentiation
- Effector plasma cells (secrete antibodies)
- Memory cells formed
How is lymphocyte receptor diversity generated?
Random gene rearrangement
What is somatic recombination and where does it occur?
Rearrangement of gene segments (V, D, J) → unique BCRs/TCRs
Occurs in BM (B cells) & thymus (T cells) during L devt
What is clonal deletion and why is it necessary?
• Clonal deletion = Apoptosis of self-reactive B/T cells during development
• Prevents autoimmunity → ensures central tolerance to self-antigens
What is positive selection of T cells?
• Positive selection = survival of T cells that weakly bind self-MHC on thymic epithelial cells
• Ensures T cells are MHC-restricted → can recognize antigens presented by self-MHC
What is negative selection of T cells?
• Negative selection = deletion of T cells that bind self-antigen + self-MHC with high affinity
• Prevents autoimmunity → promotes central tolerance in the thymus
What happens when a naive lymphocyte encounters its specific antigen?
Clonal selection = Ag selects spec L clone → cleanly expansion + diff
What is clonal expansion?
Proliferation of selected Ag-specific LC clone
What is the role of memory cells?
Memory b cells reside in LNs → ready to launch faster + stronger IR upon reexposure
What are the effector cells produced by activated B cells and T cells?
Activated b cells →
- plasma cells → secrete Ab
- memory cells
Activated T cells
- cd4+ → TH1, th2, th17
- cd8+
- Treg
What is meant by “one cell, one receptor” in adaptive immunity?
Each b/T cell expreses unique Ag receptor
- gen by random gene rearrangement
- ensures spec for 1 epitope per cell
