Defective interferon-gamma production in ataxia-telangiectasia.

The in vitro production of interferon-alpha and -gamma (IFN) by peripheral blood mononuclear cells from four patients with ataxia-telangiectasia was compared to that of healthy controls. Normal values of IFN-alpha were obtained in all cases. However, patients with ataxia-telangiectasia showed a great reduction or absence of IFN-gamma production after induction with either staphylococcal enterotoxin B or galactose oxidase. This defect was accompanied by the absence of secretion of another lymphokine, namely, interleukin 2 (IL-2), in one case. Lymphoproliferative response to phytohemagglutinin (PHA) was severely depressed in all patients. Near normal values of T lymphocytes were found, but the ratio of OKT4+/OKT8+ subsets was reduced in most patients, due to a decrease of OKT4+ lymphocytes. Deficiency of IFN-gamma may contribute to the abnormalities of immune functions and immunoregulation observed in ataxia-telangiectasia, and it may represent an additional cause of the high incidence of viral infections and neoplasia in this disease.