MONOCLONAL-ANTIBODIES DEFINING FUNCTIONAL SITES ON THE TOXIN SUPERANTIGEN STAPHYLOCOCCAL-ENTEROTOXIN-B

Four monoclonal antibodies (mAbs) were produced binding to four nonove rlapping epitopes on the superantigen staphylococcal enterotoxin B (SE B). The mAbs were tested for their ability to detect SEB bound to majo r histocompatibility complex (MHC) class II, to inhibit SEB binding to MHC class II, to inhibit SEB stimulation of T cell hybridomas, to bin d to various nonfunctional mutants of SEB, and to capture and present SEB and its mutants to T cells in the absence of MHC class II. We conc luded that two mAbs, B344 and B327, bound to epitopes not required for superantigen function, one mAb, 2B33, blocked an MHC interaction site on SEB, and the fourth mAb, B87, blocked the T cell recognition site on SEB. Moreover, two mAbs (B344 and 2B33) were capable of presenting SEB, although much less efficiently than APC, to CD4(-) but not CD4(+) T cell hybridomas. The results confirm the functional domains on SEB originally defined by mutation and show that MHC class II is not alway s an essential component of the superantigen ligand.