We examined mononuclear cell subsets in cord blood of normal newborns by surface marker analysis. The percentages of T lymphocytes (E-rosetting and T3⁺ cells) were lower in cord blood than in peripheral blood (PB) from adults, while the percentage and absolute number of T6⁺ cells were higher in cord blood. As the sum of T4⁺ and T8⁺ cells exceeded the values of E-rosetting lymphocytes in cord blood, we suggest that immature lymphocytes with the phenotype of ‘common’ thymocytes (T6⁺, T4⁺, T8⁺) are present in cord blood of full-term newborns. Higher percentage and absolute number of B lymphocytes were detected in cord blood. More than 50% of B cells in cord blood formed rosettes with mouse erythrocytes, a surface marker of functional immaturity. Finally, cells bearing receptors for IgG-Fc fragments or C3 and expressing Ia-like and Ml antigens were uniformly increased in cord blood, suggesting higher percentages of cells of the monocytic lineage.

Previous reports indicate depression of cellular immunity during pregnancy. In order to get a deeper insight into the immunoregulatory subsets of mononuclear cells in pregnant women, we analyzed the percentages of T and B lymphocytes, T cell subsets and cells expressing IgG-Fc and C3 receptors, and M1- and Ia-like antigens in venous blood samples from healthy women and pregnant women at different gestational ages and after delivery. Even if a trend toward a progressive decrease of T lymphocytes and T4+ helper subset was observed throughout pregnancy, along with a slight increase in the percentages of cells bearing C3 receptors, M1, and Ia-like antigens in the second trimester of gestation, analysis of variance of our data did not demonstrate statistical significance in the observed changes. Therefore we conclude that the pregnancy-induced suppression of maternal responsiveness towards alloantigens and/or mitogens is not reflected by significant changes in the distribution of circulating mononuclear cells and immunoregulatory T-lymphocyte subsets as defined by the currently available surface marker techniques.

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