Human triclonal anti-IgG gammopathy. III. Determination of the clonal persistence of the IgM autoantibody for a four and one-half year period.

The persistence in the structure of IgM anti-IgGs obtained from the serum of a patient (Gil) with Felty's syndrome was studied. Co-isoelectric focusing experiments showed that intact IgM from early (1970) and late (1973) sera, and their heavy and light chains had identical isoelectric points (pI). Light chains from 1970, 1973, and 1974 IgM-Gil had identical amino terminal amino acid sequences and belonged to the v Kappa II light chain subgroup. Specificity studies of IgM-Gil isolated from serum obtained in 1970, 1972 and 1974 showed identical patterns of reactivity with IgG and IgG subunits of all gamma chain subclasses. Finally, by haemagglutination-inhibition, antisera specific for idiotypic determinants of IgM-Gil-1970 were shown to be shared by IgM from 1970, 1972 and 1974 sera. The data support the notion that autoantibody-producing cell clones persist unaltered during the course of an untreated autoimmune disease, in this instance for 4 1/2 years.