Binding competition of toxic shock syndrome toxin 1 and other staphylococcal exoproteins for receptors on human peripheral blood mononuclear cells.

Binding of toxic shock toxin 1 (TSST-1) and staphylococcal enterotoxin A (SEA) to human peripheral blood mononuclear cells (PBMC) was investigated by using 125I-labeled ligands. Scatchard analyses revealed similar numbers of receptors (approximately 5,000 to 8,000) and similar dissociation constants (Kd, approximately 20 to 25 nM) per PBMC. SEA but not enterotoxin B, C1, C2, C3, D, or E significantly inhibited binding of 125I-TSST-1 to PBMC. Cross-competition of TSST-1 and SEA in binding assays suggests that they may bind to overlapping or separate epitopes on the same receptor.