UC Riverside

Continuous exposure to aerosolized allergens leads to the activation of the innate and adaptive immune system in the lung. Systemic inflammation in peripheral tissues has the potential to trigger activation of the brain’s resident immune cell, the microglia. Here we test whether airborne exposure to a common allergen, Alternaria alternata for 7 days at levels sufficient to trigger lung inflammation is sufficient to trigger activation or changes in homeostasis of microglia within the learning and memory region of the murine brain (the hippocampus). We specifically quantify the morphological structure of microglia in the hippocampus CA1 region by performing Sholl analysis on microglia visualized with antibodies against IbaI using the Neurolucida®360 software. Analysis revealed an increase in microglial process length in both sexes of mice exposed to allergen. However, a shift in morphology associated with reactive activation of microglia was only observed in female mice exposed to allergen. These data suggest that airborne exposure to a natural fungal allergen is sufficient to cause changes in hippocampal brain tissue that are different between sexes, with microglia in exposed females being more responsive than microglia in exposed males.