Immunosuppressant effect of gold on IgG subclasses and IgE; evidence for sparing of Th2 responses.

We set out to examine the effect of gold treatment on the Th2-dependent antibodies IgG4 and IgE in relation to other IgG subclasses in patients with rheumatoid arthritis (RA). Eighty-five gold-treated RA patients and 82 RA controls were studied. Serum IgG subclass concentrations were measured by ELISA, IgE was measured by automated enzyme immunoassay. Samples were studied serially in 13 gold-treated patients and in 11 patients with gold-induced adverse events. There was a significant reduction in the concentration of IgG1, IgG2 and IgG3 in gold-treated RA patients compared with RA controls (P 0.004-0.019), whereas IgG4 was less significantly reduced in gold-treated patients (P = 0.044) and there was no difference in IgE. In serial samples there was a significant fall in the concentration of IgG1 (P = 0.001), IgG2 (P = 0.001) and IgG3 (P = 0.026) with time but no change in IgG4 and IgE. The development of gold-induced adverse events was not associated with any change in the concentration of each IgG subclass or IgE. Deficiencies of IgG subclasses were found in 30% of gold-treated RA patients and 8.5% of RA controls, and were associated in gold-treated patients with a longer disease duration (P = 0.003) and with erosive disease (P = 0. 03). IgG2 was affected most frequently and in the majority of these cases subnormal specific IgG2 binding to widespread polysaccharide antigens (Pneumovax II) was found. Gold induces an overall immunosuppressant effect on IgG subclasses, with a deficiency in 21. 5%, adjusted for controls. The effect on the Th2-dependent antibodies IgG4 and IgE is less marked, suggesting a sparing of Th2 responses.