Imbalances of IgG subclasses and gene defects in patients with primary hypogammaglobulinemia.

The chance mating of persons with structural or regulator gene abnormalities might be expected to result in individuals who lack the capacity to synthesize specific types of heavy chains and manifest as hypogammaglobulinemia. Disproportionate levels of IgG subclasses would then be expected since the heavy chains are synthesized at separate although closely linked loci. Several instances of such alterations in subclass concentrations have been found. One family has been encountered with probable structural gene abnormalities in the autosomal Gm loci. In addition to their genetic implications, IgG-subclass imbalances are of importance because of the variable distribution of biologic properties of immunoglobulins among the IgG subclasses, and because of the observation that certain antibody populations may be markedly restricted or limited to a single IgG subclass.