Comparative analysis of the suppression by cord blood mononuclear cells of adult and neonatal lymphocytes

The spontaneous or in vivo generated suppressor cell activity of adult and cord blood has been quantitated and compared in a system that examines the regulation of the T-cell response to mitogen. We confirmed previous findings that spontaneous suppressor cell activity is stronger in cord blood. This is only true, however, in a system that uses adult lymphocytes as responder cells. Cord blood responder cells are significantly more resistant to suppressor signals than are adult cells. Thus, the influence of cord blood suppressor cells on cord blood effector cells is equivalent to that seen in similar cocultures containing only adult cells. Spontaneous suppressor cell activity decreases rapidly among cultured adult cells but remains unaffected in cultures of cord cells for at least 4 days. Suppressor cell activity induced by concanavalin A (Con A) was significantly greater with adult cells. The sum of the spontaneous and Con A-induced suppressor cell activity among both cord and adult mononuclear cells was identical, indicating that the total potential suppressor cell function of the two populations is similar and that assays of spontaneous or Con A-induced suppressor cell activity are likely to be examining the same cell population. These findings strengthen the hypothesis that while fetal immunoregulatory cells may be potent suppressor of maternal (adult) lymphocytes, internal (fetal) balance is maintained by having responder cells relatively resistant to these fetal suppressor cells.