Naturally occurring non-T suppressor cells in pregnant and neonatal mice: some functional and phenotypic characteristics.

The mammalian fetus thrives in the presence of a maternal immune system which is considered capable of initiating an aggressive reaction against alloantigens expressed on fetal cells. The control of harmful immunological reactions during pregnancy may be due in part to the combined action of soluble immunoregulatory factors and suppressor cells in the maternal/fetal environments. In the present investigation, a comparison has been made between naturally occurring splenic suppressor cells isolated from neonatal and pregnant adult CBA/J mice. Functional analysis of inhibitory activity was carried out using conventional one-way allogeneic mixed lymphocyte reactions (MLR) consisting of adult CBA/J spleen cells responding against mitomycin C-inactivated BALB/cJ spleen cells. Suppressor cells in the spleen of pregnant animals as well as a population of inhibitory cells in newborn spleen could be shown to be highly resistant to cytotoxic pretreatment with anti-T cell serum plus complement. Both newborn and pregnant non-T suppressor cells were shown to be agglutinated by the B cell-specific lectin soybean agglutinin. The densities of these two populations of non-T inhibitory cells, as determined by Percoll gradient centrifugation, were demonstrated to be very similar (ie, within the range of 1.067 to 1.043 g/ml). The striking parallels in the functional and phenotypic characteristics of the non-T suppressor lymphocytes found in the spleen of pregnant and neonatal animals suggest a common mechanism for their induction.