To evaluate the role of tumor necrosis factor-a (TNF-a) in neuronal injury in experimental group B streptococcal meningitis, infected neonatal rats were treated with a monoclonal antibody against TNF-a (20 mg/kg intraperitoneally) or saline given at the time of infection. Histopathology after 24 h showed necrosis in the cortex and apoptosis in the hippocampal dentate gyrus. Treated animals had significantly less hippocampal injury than did controls (P õ .001) but had similar cortical injury and

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... cerebrospinal fluid (CSF) inflammation. The antibody was then administered directly intracisternally (170 mg) to test whether higher CSF concentrations reduced inflammation or cortical injury. Again, hippocampal apoptosis was significantly reduced (P õ .01), while cortical injury and inflammation were not. Thus, TNF-a played a critical role in neuronal apoptosis in the hippocampus, while it was not essential for the development of inflammation and cortical injury in this model.