Clostridium difficile lacks detectable superantigen activity.

Clostridium difficile colitis causes striking leukocytosis. We examined the possibility that toxins A or B, or other nontoxin products of C. difficile, act as superantigens, thereby stimulating leukocytosis. Our results failed to show major histocompatibility complex class II-dependent T lymphocyte proliferation, the hallmark of superantigen activity. Elevated white blood cell counts in C. difficile colitis are probably due to increased generation of cytokines such as interleukin-6 (IL-6) or IL-8.