Common variable immunodeficiency (CVI) is a syndrome characterized by hypogammaglobulinemia, recurrent bacterial infections, and increased occurrence of both autoimmune disease and malignancy. In our study we examine the expression of lymphokine genes in mitogen-activated T cells from four patients with CVI. T cells from patients with CVI did not differ significantly from normals in total T cell number, CD4/CD8 ratio, CD45R expression, or proliferation in response to PHA. However, T cells from this group of patients did exhibit significant abnormalities of mitogen-induced lymphokine gene expression. T cells from patients exhibited significantly decreased expression of IL-2, IL-4, IL-5, and IFN-gamma when compared to normal controls. In contrast to these abnormal findings, mitogen-activated T cells from patients with CVI expressed normal amounts of IL-2R alpha and c-myc suggesting that these patients have a selective abnormality of T cell activation. Furthermore, it is likely that the deficient production of IFN-gamma by patient T cells is partially due to the abnormality of IL-2 production as the levels of IFN-gamma mRNA detected during the initial IL-2-independent phase of T cell activation were normal and the addition of exogenous rIL-2 was able to normalize IFN-gamma production by PHA-stimulated patient cells. Finally, supernatants from PHA-activated cultures of patients PBMC were deficient in their ability to support Ig secretion by Staphylococcus A Cowan's-activated normal B cells suggesting that these T cell abnormalities may contribute to the pathogenesis of this syndrome.