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 ant ibodies IgG4 and IgE in relation to other IgG subclasses in patients with r heumatoid arthritis (RA). Eighty-five gold-treated RA patients and 82 RA co ntrols were studied. Serum IgG subclass concentrations were measured by ELI SA, IgE was measured by automated enzyme immunoassay. Samples were studied serially in 13 gold-treated patients and in 11 patients with gold-induced a dverse events. There was a significant reduction in the concentration of Ig G1, 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 p atients (P = 0.044) and there was no difference in IgE. In serial samples t here 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. T he development of gold-induced adverse events was not associated with any c hange 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 co ntrols, 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. Go ld induces an overall immunosuppressant effect on IgG subclasses, with a de ficiency in 21.5%, adjusted for controls. The effect on the Th2-dependent a ntibodies IgG4 and IgE is less marked, suggesting a sparing of Th2 response s.