9 TCR and B cells Flashcards
Why at least 2 different mechanisms are needed
cellular - inside cell
humoral - outside cell
cellular
inside the cell will recognise and kill
humoral
if outside the cell produce antibodies to fight it off
what is involved in the cellular response
Cytotoxic T cell binds to the complex through MHC class 1
Cytotoxic T cell proliferates
Form specific cytotoxic T cells with receptors for the particular peptide circulating in the body
what is involved in the humoral response
Antigen outside the cell Internalise antigen Breaks it down Peptide presented via MHC 2 Specific T cell to peptide presented = B cell activation = antibodies
what makes up TCR complex
T cell receptor together with CD3
Which are the main receptors involved in Ag recognition
TCR binds Peptide +MHC I
Ab (M&D) binds antigens
TCR binds Peptide + MHC II
= all lead to immunoglobulin superfamily of proteins
what does the TCR depend on
Cell surface expression of the TCR depends on coexpression of the CD3 molecule
Classical TCR consist of
alpha + Beta chains
- Alpha = chromosome 14
- Beta = chromosome 7
why are TCR difficult to isolate
they are cell bound not secreted
What follows the binding of peptide and MHC by TCR
CD28 activates a signal transduction pathway to provide its co-stimulatory signal for T cell activation.
Another means to control T cell activation is by expressing factors that down-regulate T cell activation
- cascade of events involving PTK protein tyrosine kinases
what does T cell activation need
T cell activation also requires a co-stimulatory signal involving interaction of CD28 on the T cell with CD80 or CD86 (B7 family genes) on the antigen-presenting cell
Key events on B cell activation
IL-4R or BCR signal
what happens if no further signal from IL-4R or BCR
cell death
what does the IL-4R and BCR signals cause
up regulation of
CD80
MHC II
FAS
rescue from cell death
