Studies on circulating immune complexes. III: Kinetics of the immunoglobulin class of circulating immune complexes in...

The IgG, IgA and IgM classes of circulating immune complexes (CIC) were examined in 49 patients with systemic lupus erythematosus (SLE). The presence of the IgG class of CIC (IgG-IC), IgA class of CIC (IgA-IC) and IgM class of CIC (IgM-IC) was observed in 39.4%, 24.2% and 35.3%, respectively. During the course of the disease, the levels of IgG-IC and IgM-IC remained generally higher than that of IgA-IC. The patients were divided into three groups, according to the changes in IgG-IC. Group 1: these had IgG-IC persistently, associated with clinically active features (active stage). The presence of IgA-IC was occasionally transient, although IgM-IC did coexist. Group 2: these showed an increased level of IgG-IC, associated with a tendency to relapse (flaring up stage). IgM-IC disappeared occasionally, although IgA-IC appeared to be persistently present. Group 3: these showed levels of IgG-IC which decreased or disappeared and the clinical activity tended to subside (remissible and inactive stages). All classes of CIC tended to disappear. That is to say, IgG-IC, then IgA-IC, and finally IgM-IC decreased in that order. Either IgA-IC or IgM-IC was present alone persistently in a few cases. The correlations between each class of CIC and the immunological parameters were investigated. IgG-IC and IgM-IC were closely related to anti-nuclear antibody, but not to anti-DNA antibody.(ABSTRACT TRUNCATED AT 250 WORDS)