Objective: To characterize the initial events in anti-Ro production by a patient with systemic lupus erythematosus, in whom this autoantibody is developing.
Methods: The immune response to the Ro ribonucleoprotein and other autoantigens were studied by enzyme-linked immunosorbent assay for IgG and IgM, by isoelectric focusing, and by inhibition studies to determine apparent avidity.
Results: The patient's sera showed an oligoclonal response to Ro that increased in complexity and affinity with time. IgM anti-Ro appeared shortly before IgG anti-Ro, and disappeared as IgG anti-Ro increased in titer and affinity. IgG antiribosomal P autoantibodies also appeared during the patient's course, but in contrast to anti-Ro, were not preceded by IgM antiribosomal P.
Conclusion: These data are consistent with the Ro autoantigen being presented and processed in a manner similar to heterologous antigen, and with differences in the mechanisms that lead to the production of IgG anti-Ro autoantibodies as opposed to antiribosomal P autoantibodies.