The results regarding the studies investigating the involvement of humoral immunity in ALS are rather inconsistent: in one study, no differences were found between the levels of IgG, IgM, IgA, in addition to the complement component C3 in ALS patients and controls (Bartfeld et al., 1982), whereas in another study, elevated mean serum IgG values were observed in a small group of ALS patients (Tavolato et al., 1975). This evidence concerns the gene C3 and amyotrophic lateral sclerosis.