RESUMEN
Antibodies against cross-reactive idiotypes (CRIs) may prove useful as phenotypic tracers of immunoglobulin variable region genes (VH or VL). CRIs of human rheumatoid factors (RFs) seem to be useful in the elucidation of the incidence and structural characteristics of the latter. Anti-Wa CRI antibodies were produced and an enzyme immunoassay was developed to test polyclonal RFs isolated from sera of 20 rheumatoid arthritis (RA) patients, 7 males and 13 females, aged 17 to 74 years. Seventeen patients had clinically active disease and three were in remission. Disease duration ranged from 1 to 25 years and RF titers ranged from 1:160 to 1:640. The immunoassay could detect as little as 8 ng of a monoclonal purified WaRF and positive results were found in 30 per cent of patient sera. Therefore, we may conclude that at least part of the RFs seen in RA patients derives from germ line genes