STIMULATORY AND CYTOTOXIC ACTIVITY ON HUMAN ADULT AND FETAL LYMPHOCYTES BY HETEROLOGOUS ANTIHUMAN FETAL LYMPHOCYTE SERA

Antisera against human fetal peripheral blood lymphocytes, thymus, and spleen cells were raised in 14 rabbits and tested for mitogenicity and cytotoxicity against maternal, cord blood, and fetal lymphocytes. Although both antilymphocyte serum (ALS) and antispleen serum were cytotoxic, only antithymus serum (ATS) proved to be a potent mitogen as well. The cytotoxic titers of various ATS correlated roughly to their mitogenic activities. The magnitude of the response of maternal, cord blood, and fetal lymphocytes to ATS was often equal to that of leukoagglutinin (LA), which was used as a reference mitogen. After repeated absorptions with human buffy coat cells, the mitogenic effect of ATS increased further. Maternal lymphocytes often reacted more weakly than cord or fetal lymphocytes. Absorption of ATS with adult buffy coat cells removed the cytotoxicity against fetal peripheral lymphocytes but not against fetal thymocytes and splenocytes. After a few absorption steps with fetal thymus cells, the mitogenic capacity of ATS against fetal thymocytes clearly rose, whereas the mitogenicity was unchanged when fetal spleen cells were used as absorbant. On the contrary, both maternal and cord blood lymphocytes reacted more avidly when ATS was absorbed with adult spleen cells. However, absorption with adult thymus cells did not increase the mitogenic activity to such an extent. ATS was not organ-specific or fetal-specific. Not even exhaustive absorptions yielded strong specific antisera. Nevertheless, attempts are being made to find an antiserum specifically mitogenic to fetal but not to maternal lymphocytes. © 1979 by The Williams & Wilkins Co.