Immunology 5-6 Flashcards
What is an epitope?
A region of an antigen where the receptor on cell binds.
What is the BCR?
A transmembrane protein composed of Ig-alpha and Ig-beta and disulphide heterodimers.
What process increases BCR diversity?
Immunoglobin gene rearrangement
Which chains undergo more rearrangement?
Heavy chains
What is required to activate T or B cells?
An antigen as well as an accessory signal either from other T cells or microbial constituents.
What is the advantage of a T cell accessory signal?
Has memory and involves all Ig classes.
What is the process of B cell activation?
1) BCR recognises foreign antigen
2) Foreign antigen is internalised and degraded
3) Degraded peptides are then associated with “self” and displayed on the surface of the cell
4) Displayed peptides are recognised by CD4+ cells, activating the B cell.
5) T cell derived cytokines bind to receptors on B cells
6) B cells proliferate and differentiate into plasma cells and memory cells.
What MHC class are CD4+ cells associated with?
MHC II (extracellular)
What MHC class are CD8 cells associated with?
MHC I (intracellular)
How are abnormal TCRs prevented?
A checkpoint is put in place to check functionality of ht beta chain. If it is not functional, the TCR is deleted by apoptosis.
Why is it bad if a TCR binds too strongly to the MHC molecule?
It can lead to cell signalling even in the case of “self” antigens, leading to autoimmune diseases.
What percentage of thymocytes survive selection?
5%
What are MHC molecules?
A small sample of the internal contents of a cell displayed on the surface for possible immune cell recognition. Markers of “self” and indicate health of a cell.
What gene are the MHC molecules encoded on?
HLA gene (human leukocyte antigens) - codominant expression.
What forms make up Class I?
HLA-A
HLA-B
HLA-C
