IAH5 - Adaptive immunity 1 Flashcards
What 3 signals activate T cells?
Recognition of antigen
Co-stimulation
Cytokines
Name the highly variable antigen receptors recognising structures that are specific to individual pathogens on T and B cells
T cell receptor (TCR)
B cell receptor (BCR)
How are antigens presented by APC?
MHC
What is the purpose of specific antigen receptors?
Adaptive immunity with greater sensitivity and specificity
What make MHC difficult for pathogens to evade immune response?
Polygenic (contains many MHC genes - so every individual has different peptide binding specificities
Polymorphic - multiple variants of each gene within population
MHC class I
a) presents to…
b) expressed on …
a) CD8 (cytotoxic T cells)
b) Most nucleated cells
MHC class II
a) presents to…
b) expressed on …
a) CD4
b) APC and cells in the thymus
DC, macro, B, fibroblasts, epithelium
Which MHC is associated with beta 2 microblobulin?
Class I
Describe endogenous pathway?
Assembly of MHC class I antigen complex
Antigen broken down by proteasome in cytoplasm Peptide to ER where they bond MHC class I, packaged and modified in Golgi, displayed on cell membrane and binds CD8
Describe exogenous pathway?
Assembly of MHC class I antigen complexes
pathogen taken up by phagocytosis, proteolysis breaks down e.g. lysozyme, MHC class II fuses with antigen containing vesicle, displayed on surface and binds Cd4
How and where are TCRs made?
Thymus
Random somatic DNA recombination (RAG enzyme)
What is positive selection?
T cell selected when it can recognise MHC (it is MHC restricted)