Nature and properties of cytotoxic plasma activity in amyotrophic lateral sclerosis

Cytotoxic activity of plasma towards normal red blood cells in patients with amyotrophic lateral sclerosis (ALS) has been studied as a function of progressive plasma dilution and compared with plasma from patients with Charcot–Marie–Tooth's disease (CMT). At progressive dilution the hemolysis by ALS‐plasma showed a specific pattern that differed qualitatively and quantitatively from that of normal plasma as well as CMT and persisted up to a dilution of 1:6561. Differences in dilution pattern were found when comparing different clinical types of ALS. There was evidence for a partial complement dependancy of the reaction that brings about the hemolysis provoked by ALS plasma. Experiments with plasma fractionated by gel filtration and with isolated immunoglobulins produced evidence for cytotoxic properties of IgA and IgG from ALS plasma. The observations speak in favor of a consistency between the observations of plasma cytotoxicity in ALS and earlier observations on immunological abnormalities in the disease.