IgG2 deficiency in sickle cell anaemia.

8 patients with known sickle cell anaemia were studied immunologically. The concentrations of the main immunoglobulin classes, IgG and IgA, were significantly higher than the levels in 11 normal age- and sex-matched black subjects (P less than 0.01). IgM levels were not significantly different in the two groups. There was a heterogeneity in the interaction of the IgG subclasses with Protein A, with low levels of IgG2. The IgG2:IgG1 ratios varied from 1:3.8 to 1:6 (normals 1:3). In 4 patients the absolute levels of IgG2 as measured by radial immunodiffusion were lower than normal, thus confirming the chromatographic ratios. Since specific antibody is often restricted to a single subclass, the levels of IgG subclasses may be related to recurrent bacterial infections in these patients.