Major Histocompatibility Complex Flashcards
What does MHC stand for?
Major Histocompatibility Complex
Lymphocytes (B and T cells) are
‘adaptive’ immune cells
b and t cells are life […]
life long
what percentage pf leukocutes are Lymphocytes?
20 -40 % of total leukocytes
Prior to interactions with antigen, lymphocytes are…
… naive
Immature B and T cells are
… small, motile non
phagocytic cells and morphologically
identical (although each has a unique receptor)
Prior to interactions with antigen (naïve), lymphocytes are in…
… G0 (quiescent) but can be induced into cell cycle via Ag stimulation
As they progress through cell-cycle they
proliferate and differentiate
3
Lipids / nucleic acids need to be
linked to proteins or polysaccharides to be immunogenic
Proteins are the most
potent immunogen
WHAT MAKES A GOOD IMMUNOGEN?
1) Foreigness
2) Molecular size
3) Chemical composition
4) ABility to be recognised.
Describe foreigness of immunogens?
must be recognised as non-self (B and T cell are educated to recognise ‘self’
whats the best molecular size?
> 100 kDa best; 5 – 10 kDa poor
B and T cells differ in …
… antigen recognition
describe chemical composition of immunogens?
homopolymers
copolymers (2 different amino acids)
B cells interact with soluble (and processed) antigen via…
… the B cell receptor
5
epitopes must be …
… accessible as Ag may be free in solution
T cells interact with
internally processed Ag (peptide associated with MHC molecules on the surface of antigen presenting cells - APC or ‘altered-self’ cells.
Thus T cells must be…
… shown processed antigen to become activate
Two classes of T cells (broadly)…
T cytotoxic cells (CD8 +)
T helper cells (CD4+)
T cytotoxic cells (CD8+) function?
they are killer cells involved in Ag-specific cell killing of altered self cells.
T helper cells (CD4+) function?
secrete cytokine - coordinate immune response