Transplacentally acquired maternal T lymphocytes in severe combined immunodeficiency: a study of 121 patients

A study in 121 infants with severe combined immunodeficiency (SCID) was per formed to determine the prevalence of an engraftment by transplacentally ac quired maternal T cells and to explore clinical and immunological findings related to this abnormality. Each newly diagnosed patient with SCID present ing with circulating T cells was evaluated for chimerism by performing sele ctive HLA typing of T cells and non-T cells. In patients with engraftment, maternal T cells were characterized phenotypically and functionally, and re sults were correlated with clinical findings in the patients. Maternal T ce lls were detected in the circulation in 48 patients; these cells ranged fro m fewer than 100/muL in 14 cases to more than 2000/muL in 4 cases (median, 415/muL). Clinical signs of graft-versus-host disease (GVHD) were absent in 29 patients. In the other cases, manifestations of GVHD were present, invo lving the skin and in 14 cases also the liver. Skin GVHD was mild in 8 pati ents. In these patients, as well as in patients with no signs of GVHD, mate rnal T cells were predominantly CD8(+) and, with one exception, failed to r espond to mitogen stimulation. In 9 patients, manifestations of skin GVHD w ere prominent. T cells in these cases were predominantly CD4(+) and respond ed, with one exception, to mitogen stimulation. In 8 of the cases with prom inent skin GVHD, the underlying SCID variant was characterized by the absen ce of B cells. In this study, further understanding is provided of a phenom enon that is responsible for the significant heterogeneity of clinical and immunological findings in SCID.