Adaptive Immune Recognition Flashcards
What are the key adaptive immune cells?
B and T lymphocytes.
List 2 functional differences between B and T lymphocytes.
1 - B lymphocytes are responsible for the humoral response via antibodies, whereas T lymphocytes are responsible for the cellular response.
2 - B cell receptors are able to be secreted by the cell, whereas T cell receptors are not able to escape the cell surface.
What is a B cell receptor?
How does it differ from a T cell receptor?
- A B cell receptor is a surface immunoglobulin (antibody) that has not been secreted.
- A T cell receptor is similar in structure, however consists only of one alpha chain (analogous to a light chain) and one beta chain (analogous to a heavy chain).
Which gene segments are contained within light chains only?
Only variable (V) and joining (J) - not diversity (D), which is only present in heavy chains.
Which chains of a T cell receptor rearrange first?
Which gene segments rearrange during the formation of T cell receptors?
Beta chains rearrange first (like heavy chains in B cell receptors).
- Variable (V), diversity (D) and joining (J) chains all rearrange.
Describe the roles of 2 enzymes involved in gene rearrangement.
- Rearrangement is coordinated by RAG (an enzyme which is able to excise and repair DNA).
- Further diversity is created by TdT (an enzyme which produces point mutations).
How is the way in which B cell receptors recognise antigens different to the way in which T cell receptors recognise antigens?
- B cell receptors can recognise whole antigens through surface patterns.
- T cell receptors can only recognise short amino acid sequences, and antigens must be processed by antigen presenting cells using the major histocompatibility complex (MHC).
What is the human leukocyte antigen (HLA)?
A gene complex encoding the major histocompatibility complex.
What is the functional difference between MHC Class I and II proteins?
- MHC class I proteins mainly present peptides derived from proteins within the cell. This is a way of dealing with pathogens that have already invaded the cell.
- MHC class II proteins mainly present peptides derived from extracellular pathogens.
Which T cells bind to MHC class I proteins (via T cell receptors)?
CD8 (cytotoxic) T cells.
Which T cells bind to MHC class II proteins (via T cell receptors)?
CD4 (helper) T cells.
To which domain of the MHC class I proteins do T cells bind?
The alpha 3 domain.
To which domain of the MHC class II proteins do T cells bind?
The beta 2 domain.
List 2 responses of T cells binding to MHC class I proteins via T cell receptors.
1 - Proliferation.
2 - Lysis of the target cell (the cell expressing the MHC).
List 2 responses of T cells binding to MHC class II proteins via T cell receptors
1 - Proliferation.
2 - Secretion of cytokines by the CD4 cell.
