MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-II BINDING-SITE FOR STREPTOCOCCAL PYROGENIC (ERYTHROGENIC) TOXIN-A

Streptococcal pyrogenic exotoxin A (SPEA) is an important pathogenicit y factor of group A streptococci. It is a member of the family of ''su perantigens'' produced by Staphylococcus aureus and Streptococcus pyog enes and its T lymphocyte stimulating activity is involved into the pa thogenesis of certain diseases: caused by pyogenic streptococci. In th is study we have produced and characterized recombinant SPEA molecules in Escherichia coli. These molecules are indistinguishable from natur al SPEA in both T cell stimulatory and HLA class II binding activities . Human class II molecules are more efficient than mouse class II mole cules in presenting SPEA to T cells. In binding tests to major histoco mpatibility complex class II-positive cells SPEA competes with staphyl ococcal enterotoxin B and A but not with toxic shock syndrome toxin-1.