Human serum reacting specifically with a subset of beta-tubulin isoforms

The serum of a patient suffering from myeloma was found to decorate microtubules and mitotic spindles of cultured cells. Immunoblots performed after one- and two-dimensional electrophoresis showed a reaction with a certain subset of beta-tubulin isoforms, but not with beta'- and alpha-tubulins. The tubulin subset contained both ubiquitous (beta-3) and neurospecific (beta-4,5,6) isoforms. An IgM lambda and an IgA kappa myeloma protein were found in this serum. Immunoblots performed with specific anti-isotype second antibodies showed that the tubulin subset could be evidenced using anti-mu, alpha, lambda, and kappa-specific antisera. Moreover, the tubulin subset was also evidenced using an anti-gamma second antibody. These results, which do not exclude a participation of the myeloma proteins in the anti-tubulin reactivity, indicate, however, that the antibody response was polyclonal. The same restricted specificity of all classes of anti-tubulin antibodies of this serum favours the hypothesis that the immune response of the patient was directed against an antigen sharing epitopes with tubulin rather than with tubulin itself.