V-region-specific alterations of serum IgM production in multiple myeloma of IgG class

Multiple myeloma is accompanied by decreased polyclonal serum immunoglobulin concentrations. This suppression might be due to non-specific effects on the polyclonal lymphocyte populations as previously suggested, or it could include specific variable region-dependent mechanisms. Thus, differentiation, survival and activation to Ig secretion of B-lineage cells are dependent on the expression and signalling through the variable Ig receptor. The present study addresses the question whether such variable region-specific alterations were present in the peripheral repertoire of IgM antibodies in patients with IgG-secreting MM.

IgM reactivity repertoires towards a large panel of antigens in extracts of homologous tissues (liver, brain, stomach and heart muscle) and bacteria (Bacillus macquarensis) were analysed in sera from 22 patients diagnosed with IgG1 MM. Healthy, matched volunteers served as control donors. A modified Western assay was used, and values obtained from area integration by image analyses were submitted to multiparametric statistics.

The results confirm previous observations on the depression of serum IgM concentrations in multiple myeloma, and demonstrate concentration-independent, patient- and V-region-specific alterations in the polyclonal reactivity repertoires. Since the scoring of IgM reactivities by this technique is independent of IgG and because the deviations of IgM reactivity are not coincident with reactivities of (myeloma) IgG in the individual sera, the results indicate that the immunological syndrome of MM includes significant V-region-specific alterations in the polyclonal repertoires of IgM antibodies.