Immunoregulatory T cells in males vulnerable to Epstein-Barr virus with the X-linked lymphoproliferative syndrome.

The X-linked lymphoproliferative syndrome (XLP) is a primary immune deficiency. Affected males are vulnerable to fatal infection by Epstein-Barr virus (EBV). In patients who had survived an infection by EBV, helper and cytotoxic T cells reactive to virus-transformed autologous B lymphoblastoid cells were infrequent. This was similar to that observed in normal individuals seronegative to EBV. In contrast, frequencies of the reactive T cells were high in normal controls seropositive to EBV. Patients with XLP also had a propensity to activate radiosensitive suppressor cells when their T cells were stimulated by EBV transformed B cells. Hence, clonal expansion of helper and cytotoxic T cells to virus-transformed B cells failed to occur during an EBV infection in these patients because of immunosuppression. These defects in the T cell repertoire of patients with XLP may predispose them to be susceptible to EBV-induced lymphoproliferation and contribute to the variability in expression of the phenotypes seen in these patients.