Changes

[[Image:MHC.jpg|thumb|right|250px|Major Histocompatibility Complexes - B. Catchpole, RVC 2008]]

[[Image:MHC.jpg|thumb|right|250px|Major Histocompatibility Complexes - B. Catchpole, RVC 2008]]

=Introduction=

==Introduction==

T-cells rely on Major Histocompatability Complexes (MHC), which are molecules manufactured within cells for the purpose of presenting antigen fragments so that they can be detected by the immune system. MHC has evolved to form two classes for antigen presentation: '''MHC I''' presents digested fragments from antigen in '''cellular cytoplasm''', and '''MHC II''' presents digested fragments from antigen in the '''tissue fluid'''. MHC I tends to bind slightly smaller peptides (~9 amino acids) than MHC II (~15 amino acids).

T-cells rely on Major Histocompatability Complexes (MHC), which are molecules manufactured within cells for the purpose of presenting antigen fragments so that they can be detected by the immune system. MHC has evolved to form two classes for antigen presentation: '''MHC I''' presents digested fragments from antigen in '''cellular cytoplasm''', and '''MHC II''' presents digested fragments from antigen in the '''tissue fluid'''. MHC I tends to bind slightly smaller peptides (~9 amino acids) than MHC II (~15 amino acids).