AUGMENTATION OF NATURAL ANTIGANGLIOSIDE IGM ANTIBODIES IN LOWER MOTOR-NEURON DISEASE (LMND) AND ROLE OF CD5-CELLS( B)

IgM antibodies directed against neuronal gangliosides GM(1), GM(2), GD (1a), GD(1b) and GT(1b) occur in normal individuals and their level si gnificantly decreases with age. Patients with lower motor neuron disea se (LMND) produce high levels of these auto-antibodies. AntiGM(1) IgM is selectively augmented. In these patients, the CD5+ (B1) and CD5- (B 2) subsets of B cells are not distinct entities but range from those w ithout detectable CD5 marker to those with high CD5+ expression. B1 B cells were sorted to homogeneity, but B2 B cell cannot be isolated to homogeneity because of the presence of B1 cells with low CD5 expressio n. In short term cultures both the subsets produced IgM antibodies, bu t the antibodies reacted better with desialylated GM(1) than with GM(1 ). Cycloheximide (Cx) (0.35 mM) largely blocked IgM synthesis of the B 1 B cells but inhibition of the B2 B cells was incomplete, possibly du e to shedding of cytophilic antibodies as well as to the presence of B 1 phenotype with loss of CD5 expression. CD5+ B cells may be involved in the production elf antiglycolipid IgM.