Characterization of a cross-reactive idiotype on two human autoantibodies associated with systemic autoimmune disease

A human-human hybridoma was derived from a patient with primary Sjogren’s Syndrome. The monoclonal antibody from this hybridoma, P36, was found to be polyreactive. P36 shared idiotypic cross-reactivity with a lupus-associated monoclonal antibody called 4B4. There was a strong correlation between P36 and 4B4 idiotype levels in systemic lupus erythematosus sera. Western blot studies showed that this shared idiotype was found on the heavy chain of both antibodies. This study shows that the heavy chain is important in the expression of this idiotype and provides another immunologic link between these two rheumatic diseases.