XX T cells and XY B cells in two patients with severe combined immune deficiency.

Immunologic evaluation of two unrelated male infants with clinical and laboratory evidence of severe combined immunodeficiency (SCID) revealed T cells with a mature phenotype in the peripheral circulation of both patients although both had biopsy evidence of thymic alymphoplasia. Both had a normal number of T cells with a cytotoxic/suppressor surface marker (OKT8) but very few T helper cells (OKT4). Lymphocyte stimulation with the mitogens PHA, Con A, and pokeweed or with allogeneic cells resulted in no proliferation. However, addition of T cell growth factor, plus the phorbol ester TPA, to lymphocytes cultured with the T cell mitogen PHA did result in some proliferation of T cells. In both cases these T cells demonstrated an XX female karyotype and were probably of maternal origin. In contrast, proliferating B cells stimulated with Epstein-Barr virus demonstrated a normal XY male karyotype. The possibility that severe combined immune deficiency in these patients was the result of graft-versus-host disease induced by maternal lymphocytes is discussed.