Focal encephalitis in the Lewis rat induced by intracerebral enterotoxin superantigen and amplified by activated intravenous splenocytes.

The histological response after intracerebral (IC) injection of superantigen (SAg) was investigated in unprimed Lewis rats. The staphylococcal enterotoxins (SE) A (SEA), and E, but not B or saline, induced a variable perivascular inflammation in the injected hemisphere (6.7 +/- 6.1 cuffs per tissue section with SEA; mean +/- SD). Adoptive transfer of mitogen activated splenocytes (AS) augmented the response to SEA significantly (18.5 +/- 11.4; P<0.05). With or without AS transient bilateral perivascular cuffs were observed around the ventricles and in the corpus callosum up to 3 days after IC injection. The findings demonstrate that local expression of SAg in the brain can cause encephalitis, depending on the number of activated T cells in the circulation.