Microglial pathology is evident in rats exposed to nerve agent. Double immunofluorescent staining for microglia (OX-42) and cytokines (MCP-1 in A; IL-1α in B) in soman exposed rats. Panel A shows severe dystrophy of microglia, evident as extensive fragmentation of the cells’ cytoplasm, in the piriform cortex (arrows). MCP-1 immunoreactivity is localized in neurons. In Panel B, OX-42-positive microglia with fragmented processes also reveal IL-1α immunoreactivity in their cytoplasm (arrow). These cells showing features of both activation (IL-1) and degeneration (cytorrhexis) are thought to represent transitional forms; they were found in the dentate gyrus. Survival time is 12 hours; DAPI counterstain. Scale bar: 50 μm. Images provided by Erik A. Johnson, US Army Medical Research Institute of Chemical Defense (USAMRICD), Aberdeen Proving Ground, MD.