| Abstract: | ABSTRACT: T lymphocytes from human fetuses and newborns strongly and spontaneously suppress various adult cell functions (i.e. T-cell proliferation, B-cell differentiation, and Ig synthesis). The precise phenotype of the suppressor cell is controversial. In this investigation we use cord T-cell subsets negatively selected by the panning technique or by complement-mediated lysis using the monoclonal antibodies OKT4 and OKT8. Cord T cells deprived of the OKT4+ subpopulation exerted only a marginal suppressor activity (12 ± 7 as compared to 73 ± 4% of unfractionated T cells) on the proliferation of maternal cells in our PHA-stimulated co-culture assay using sex chromosomes as markers for dividing cord (male) and maternal cells. The suppressive effect was direct, i.e. not mediated by induction of maternal OKT8+ suppressor effector cells. Cord and maternal T-cell subsets were also tested for their sensitivity to exogenous prostaglandin E2 (PGE2) at doses varying between 1.4 × 10?5 and 1.4 × 10?9 M. Both maternal OKT4? and OKT8? T-cell subsets were highly sensitive to suppression by PGE2. In contrast, cord OKT8? T cells were essentially nonsensitive at all doses of PGE2 used, whereas cord OKT4? T cells were significantly suppressed at four out of five concentrations tested (1.4 × 10?6 through 1.4 × 10?9). Our results suggest a direct correlation between the phenotypes of the cord-suppressor and maternal-target T cells and their sensitivity to PGE2. |
