C5AR1 and Cognitive impairment: A statistically significant difference in behavior (p < .05) was observed between the Arctic mice lacking C5aR1 compared to the C5aR1 sufficient Arctic mice indicating protection from deficit in the Arctic/C5aR1KO mice relative to the Arctic mouse (Fig. 1e), consistent with the hypothesis that blocking C5aR1-mediated events prevents or slows the progression of cognitive defects.