Agnieszka Szczepek aszczepe at GPU.SRV.UALBERTA.CA
Wed Feb 22 12:55:51 EST 1995

On Wed, 22 Feb 1995, Per Tidehag wrote:
> I wounder if someone could try to explain to me, what probably is trivial, 
> what a "super-antigen" is, and how it differes from ordinary antigens.

Superantigens are molecules that bind to the V beta domain and to MHC
classII molecule simultaneously. Since the superantigens bind OUTSIDE of
the TCR/antigen site therefore any T cell with specific V beta will be
activated by a specific superantigen. 

Eg.: Staphylococcal toxin SEC1 will bind and activate all T cells 
expressing V beta12.

"Ordinary" antigen will be processed inside the antigen presenting cell
via MHCI or MHCII specific pathway (depending on the kind of the antigen
and abilities of the cells for AG processing) and then expressed on the
cell surface as a MHC/peptide complex. That complex has to be recognized
by the T cell receptor and T cell will make its decision as for its
activation. In case of the superantigen it is not recognized by TCR, it is
not processed by APC. I see it as a "crazy glue" between MHC and TCR

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