infection of human microglia activates caspase-1. A. Caspase-1 activity was not detected in mock-infected microglial cultures that were labeled with Hoescht nuclear stain. B. In contrast, microglia infected by HIV-1 showed caspase-1 activity at 24 hr post-infection (Original magnification 400X). C. Quantitation of caspase-1 activity in microglia at 4 and 24 hr post-infection showed an increased in caspase-1 activity induced by HIV-1 infection and also over time. (Mean values reported. Bars indicate standard error. Student t-test, *p < 0.05).