Immune regulation of immunoglobulin production in IgA-nephropathy

Serum immunoglobulin concentrations, percentage surface IgA-positive peripheral blood lymphocytes, and PWM- and Con A-stimulated immunoglobulin production in vitro were evaluated in patients with IgA nephropathy and normal controls. Elevated levels of serum IgA and IgM were present in 46 and 62% of patients, respectively, but the absolute concentrations of IgA₁ and IgA₂ were not different from normal values. In comparison with controls, patients with IgA nephropathy demonstrated similar numbers of surface IgG- and IgA-positive peripheral blood lymphocytes and after stimulation with PWM and Con A their lymphocytes produced similar amounts of IgG, IgA, and IgM. Separate analysis of a subgroup of patients with severe disease demonstrated significantly higher IgG and IgM production after PWM stimulation. However, serum immunoglobulin levels were not different. The number of Ig-bearing lymphocytes and the in vitro production of IgA is normal in IgA nephropathy. Excessive production of IgG and IgM in vitro is limited to patients with severe disease.