High affinity as a disease determinant factor in anti-GM₁ antibodies: Comparative characterization of experimentally induced vs. disease-associated antibodies

Elevated titers of serum anti-GM₁ antibodies of IgG isotype are found frequently in patients with Guillain-Barré syndrome. Much evidence indicates that these autoantibodies are involved in disease progression, but their exact function and the mechanism of their appearance are still unclear. In an attempt to reproduce "ganglioside syndrome", the experimental model of neuropathy developed by Nagai et al. (Neurosci. Lett. 2 (1976) 107), rabbits were intensively immunized with GM₁ in complete Freund adjuvant (CFA). High titers of anti-GM₁ antibodies were produced, with class switch and affinity maturation indicating an elaborate immune response. Unexpectedly, the rabbits did not show any clinical symptoms of neuropathy. Relatively affinities of both IgM and IgG antibodies were significantly lower than those of similar antibodies from neuropathy patients. These results suggest the existence of a threshold value above which affinity of anti-GM₁ antibodies becomes an important factor in disease induction. The absence of neuropathy symptoms in rabbits may be explained by absence of these high-affinity anti-GM₁ antibodies.