C3 and hereditary spastic paraplegia: C3 is an important complement, and some studies reported that IgG combined with immunoglobulin deposition may induce complement activation (Evans et al., 1973; Park et al., 2013).We therefore performed Spearman correlation analysis to determine the potential correlation between gut microbiota and HSP-related indexes and found that IgG was positively associated with Bacteroides, and Lachnoclostridium was negatively correlated with C3.