NATURALLY-OCCURRING ANTIIDIOTYPIC ANTIBODIES REACTIVE WITH ANTI-DNA ANTIBODIES IN SYSTEMIC LUPUS-ERYTHEMATOSUS

The levels of 'putative' anti-idiotypic antibodies reactive with F(ab' )(2) fragments of affinity purified DNA binding antibodies from five S LE patients were measured in the serum of active and inactive systemic lupus erythematosus (SLE) patients, their relatives, spouses and heal thy non-related individuals. Serum anti-idiotypic antibodies of the Ig G isotype could be detected in the serum of 8/15 inactive SLE patients , 3/19 active SLE patients, 17/27 SLE relatives, 1/4 SLE spouses and 6 /32 healthy non-related individuals. When the serum immunoglobulins fr om the individuals in each group were separated into IgG and IgM antib ody fractions and analysed, a significant increase in levels of IgG an ti-idiotypic reactivity were found in healthy individuals (16/32), whi lst no significant increase in IgG antiidiotypic antibodies were detec ted in SLE patients, SLE relatives and SLE spouses. Comparatively few individuals tested showed detectable levels of IgM anti-idiotypic anti bodies. These results demonstrate that anti-idiotypic antibodies react ive with anti-DNA antibodies are detectable in the serum of SLE patien ts, SLE relatives, SLE spouses and healthy individuals, and are predom inantly of the IgG isotype. The increased frequency of IgG anti-idioty pic antibodies after separation from serum IgM antibodies infers that anti-idiotypic activity of some Ige immunoglobulins in the sera of hea lthy individuals may be masked by the presence of IgM antibodies in th e serum.