Reduced serum level of transforming growth factor-beta in patients with IgA deficiency.

Seventeen patients with IgA deficiency, 13 subjects with selective IgA deficiency and 4 with a combined IgA and IgG2 deficiency, were assessed for serum levels of cytokines relevant for B cell differentiation. Transforming growth factor (TGF)-beta was quantified by bioassay and interleukin (IL)-4, IL-6, and IL-7 by immunoassay. The serum levels of TGF-beta were significantly lower in patients with IgA deficiency than in healthy blood donors. Of the patients with IgA deficiency, 4 had detectable IL-4 levels while 4 of the others had detectable IL-6 levels in serum. IL-4 and IL-6 were not detected in the controls. Serum IL-7 levels were similar in patients and controls. A significant, negative correlation was found between serum TGF-beta and the number of circulating B lymphocytes in the patients with IgA deficiency. No association was found between serum cytokine levels and the occurrence of infections at the time of study. Since TGF-beta has been implicated in IgA isotype switching in man, and our study demonstrates an association between low serum TGF-beta levels and IgA deficiency, dysregulation of TGF-beta might be a contributing factor in the pathogenesis of IgA deficiency.