Reduced expression of the interferon-gamma messenger RNA in IgG2 deficiency

The specific defect that causes IgG2 deficiency, which is one of the primary immunodeficiencies, is unknown. Recently, it was shown that interferon-gamma (IFN-gamma) induces synthesis of human germline C gamma 2 transcripts. In the authors' previous study and the present one, peripheral blood lymphocytes (PBLs) of all five tested patients with IgG2 deficiency failed to produce enough IFN-gamma when stimulated with phytohaemagglutinin or concanavalin A although they produced a sufficient amount of interleukin-2 (IL-2). The low level of IgG2 production in pokeweed mitogen-stimulated PBLs of four tested patients was improved by the addition of recombinant IFN-gamma. In this study, the amount of IFN-gamma messenger RNA showed various degrees of reduction in all five tested patients. Sequence analysis of the IFN-gamma coding regions and flanking regions revealed neither a point mutation nor a deletion for any of the patients. Thus the results suggest that the reduced expression of IFN-gamma messenger RNA may play an important role in the IgG2 deficiency of these patients.