The Effect of Gm (23) on the Concentration of IgG2 and IgG4 in Normal Human Serum

The IgG2 and IgG4 levels in 55 serum samples from family members with known Gm (23) genotype were studied. No correlation between IgG2 or IgG4 concentration and age or between these subclasses and sex was observed. Gm (23) shows no marked effect on the concentration of IgG2, but the concentration of IgG4 in serum is in the sequence Gm (23) homozygotes τ; Gm (23) heterozygotes τ; Gm (-23), and the differences are significant. Since the IgG4 allotype 4b appears, on the basis of limited data, to be transmitted with Gm (23), the observed relation between the Gm (23) genotype and IgG4 concentration may be due to an effect of 4b and not to Gm (23). More data are needed.