Serum IgG subclass levels in paediatric clinic patients with variable degrees of IgA deficiency.

We measured IgG subclass levels by radial immunodiffusion with polyclonal antisera in 60 patients with IgA deficiency. The low IgA levels were measured by a sensitive and specific enzymoimmunometric method. None of the patients had complete deficiency of IgG2, but 4 patients had serum levels of IgG2 and 4 of IgG3 below the range for controls. Elevated levels of IgG1 were found in patients with juvenile rheumatoid arthritis and coeliac disease. None of the patients with coeliac disease or juvenile rheumatoid arthritis had low IgG2 or IgG3 levels. The levels of IgG4 were highly variable but patients with coeliac disease had particularly high values. The severity of IgA deficiency did not correlate with the level of serum IgG2.