In vitro autoantibody synthesis by anti-La(SSB) positive SLE patients and healthy controls

In vitro production of anti-La(SSB) and anti-DNA antibodies by mononuclear cells (mnc) from systemic lupus erythematosus (SLE) patients and healthy controls was measured using ELISA techniques. The SLE patients were divided into anti-La(SSB) positive and negative groups depending on Ouchterlony analysis of the serum. Both patient groups spontaneously produced raised levels of total IgG but not IgM compared to controls. Pokeweed mitogen (PWM) stimulated mnc from anti-La(SSB) positive SLE patients and controls gave good total IgM and IgG responses. In contrast the anti-La(SSB) negative group gave no IgG but did make an IgM response. Kinetic studies showed that 14 day cultures were essential to produce detectable amounts of specific autoantibodies which, with a few exceptions, were of IgM isotype. Low levels of anti-La(SSB) and anti-DNA were spontaneously produced by anti-La(SSB) positive SLE patients and controls. PWM stimulation at least doubled autoantibody synthesis in these two groups. The anti-La(SSB) negative SLE group gave similar responses although PWM induced autoantibody levels were reduced. ConA-induced suppressor cell assay showed that anti-La(SSB) positive SLE patients could form suppressor cells but not as effectively as controls. This group of SLE patients were more successful at suppressing IgG than IgM responses.