Superantigens

[dr. jack komisar]

               Several superantigens stimulate both CD4 and CD8 T
          cells, such as streptococcal pyrogenic exotoxins A and B,
          and Mycoplasma arthritidis mitogen.  The CD8 T cell response
          to staphylococcal enterotoxins was reviewed by Herrmann and
          MacDonald in Seminars in Immunology, 5:33 (1993).  They
          raised the possibility that the proliferation of CD8 T cells
          was due to the high lymphokine titers achieved by the
          stimulation of the co-cultivated CD8 T cells, so they
          apparently did not stimulate purified CD8 T cells.  Probably
          the stimulation cannot be done without CD4 cells, because of
          the requirement for IL-2.  I don't know what is going on
          mechanistically, but Herrmann and coworkers found that the
          activation of CD8 T cells by staphylococcal enterotoxins is
          independent of the CD8 molecule, and Labrecque suggested
          that class I-restricted TCR's have a low intrinsic affinity
          for MHC class II molecules.
               The requirement for MHC class II probably depends on
          the assay and the superantigen.  SEC1 binds poorly to murine
          class II antigens.  Avery et al. (J. Immunol. 153:4853
          (1994) found that lymph node cells from class II-deficient
          mice responded strongly to SEC-1, SEC-2, SEC-3, and SEE, but
          not to SEA, SEB, or SED.

                                             Jack Komisar