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|pagetype =Blood

|pagetype =Blood

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[[Image:MHC.jpg|thumb|right|150px|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) to present antigen fragments for their recognition.  MHC has evolved to form two classes for antigen presentation: '''MHC I''' presents digestion fragments from antigen in '''cellular cytoplasm''', and '''MHC II''' presents digestion fragments from antigen in the '''tissue fluid'''.  As such, 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) to present antigen fragments for their recognition.  MHC has evolved to form two classes for antigen presentation: '''MHC I''' presents digestion fragments from antigen in '''cellular cytoplasm''', and '''MHC II''' presents digestion fragments from antigen in the '''tissue fluid'''.  As such, MHC I tends to bind slightly smaller peptides (~9 amino acids) than MHC II (~15 amino acids).