Can microglial density and morphology tell us about neuropathology in Chronic Multisystem Illness?

Abstract

A unique multisymptom illness occurred in a sizable percentage of soldiers returning from the Persian Gulf War, estimated at about 25% of soldiers. This percentage of CMI-afflicted veterans is equivalent to approximately 175,000 of the 700,000 soldiers who were involved in the Persian Gulf War. While many studies of this Gulf War illness have been undertaken and have identified prefrontal processing as a putative target, none have been undertaken to assess the neuroimmune response in the prefrontal cortex (PFC). In this study, a small sample of adult male Sprague-Dawley rats were exposed to either a vehicle control (phosphate buffered saline) or to a surrogate nerve gas agent, diisopropyl fluorophosphate (DFP) for five days. Samples of PFC from each rat were embedded in paraffin, sliced at 10 μm, and immunohistochemically stained for microglia with anti-ionized calcium binding adaptor molecule 1 (iba-1). Sections were photographed at 10X magnification and images were processed with FIJI color deconvolution and quantification software for the density of staining. Significantly reduced microglial density occurred in the experimentally exposed samples relative to the control samples. However, the number of microglia were approximately equal in the control samples relative to the experimental samples. Their morphology suggests that microglia in experimental samples, while approximately equal in number, had an amoeboid morphology, which is indicative of activation. These data suggest a role for microglia in the neuropathology of this chronic multisystem illness.