Interleukin 2 production, proliferative response, and receptor expression by cord blood mononuclear cells

To analyze the elements of the interleukin 2 (IL-2) system in newborns, the proliferative responsiveness to, production of, and expression of cell surface receptors for IL-2 were quantitated in cord blood mononuclear cells (CBMC) from 25 normal, full-term newborns and were compared to results in peripheral blood mononuclear cells (PBMC) from 15 juveniles and 28 adults in order to examine the IL-2 system as a function of age. Proliferative responsiveness of purified cord blood T lymphocytes to a saturating amount of human, recombinant IL-2 was significantly greater (p less than 0.05) than that of T lymphocytes from juveniles or adults at all three cell concentrations used. Similarly, phytohemagglutinin (PHA)--induced IL-2 production by CBMC was significantly greater (p less than 0.05) than that produced by PBMC from juveniles or adults with a mean value of 20.3U/ml compared to 11.1U/ml and 11.2U/ml for juveniles and adults, respectively. However, the proportion of CBMC and PBMC from juveniles expressing cell-surface IL-2 receptors (IL-2R) following PHA stimulation was equivalent. These results indicate a significantly enhanced proliferative responsiveness to, and production of, IL-2, but equivalent IL-2R expression, by cord blood T lymphocytes as compared to normal children and adults demonstrating that full-term newborns possess a fully competent IL-2 system at birth.