Mixed lymphocyte culture of human fetal liver cells

Objective: In order to study the immunological function of the human fetus in the first and second trimesters, mixed lymphocyte culture (MLC) of fetal liver and thymic cells was performed. MLC is a functional test to determin e human lymphocyte antigen-D incompatibilities. Methods: Human fetal liver and thymic tissue was obtained from abortions in gestational weeks 7-17.5. Forty-seven fetuses were studied with one-way MLC. The cells were stimulate d by adding irradiated fetal liver cells, adult bone marrow and peripheral blood lymphocytes. The activity was measured as DNA incorporation of radiol abeled thymidine. Results: The results indicate that the human fetus is com petent to react as early as 11-12 weeks of gestation and in some cases even earlier. In very immature fetal livers (< 8 weeks), the MLC seems to be in hibited. Conclusions: Our data suggest that the human fetus can react again st foreign transplantation antigens earlier than previous papers have claim ed. The onset of reactivity seems to differ considerably among fetuses. The present findings may explain some of the limited success of in utero trans plantations of hematopoietic stem cells in human fetuses of normal immunolo gical status. Copyright (C) 2000 S. Karger AG, Basel.