C3AR1 and amyotrophic lateral sclerosis: This is further associated increased abundance of C3 and the receptor for its C3a cleavage product (C3AR1) near ALS motor neurons (Woodruff et al., 2008; Heurich et al., 2011; Bahia El Idrissi et al., 2016), which can indirectly enhance neutrophil recruitment via their effect on other immune cells (Daffern et al., 1995; Warwick et al., 2021).