Deficient lymphokine production of newborn lymphocytes

Lymphokine production by newborn lymphocytes was assessed by measuring migration inhibition factor (MIF) and leukocyte inhibition factor (LIF) of isolated mononuclear cells from cord blood, 1-7-days-old newborns, and adult controls. Ficoll-Hypaque separated mononuclear cells were stimulated with phytohemagglutinin (PHA) or allogeneic lymphocytes in a mixed leukocyte culture (MLC), and the supernatants were harvested at optimal times for lymphokine assays. Thymidine incorporation into DNA was also assayed to calculate a proliferative index. MIF was assessed by the inhibition of adult mononuclear phagocyte cell migration under agarose; LIF was assessed by polymorphonuclear cell migration under agarose. Although the proliferative responses of cord and newborn cells are equivalent or greater than those of adult controls, the PHA-induced MIF production in cord blood and newborn lymphocytes was only 46% and 12.5% respectively of mean adult levels; MLC-induced MIF production was 44% and 7%, respectively of mean adult levels. PHA-induced LIF production in cord blood was 27% of adult levels. These differences are only appreciated if dilutions of the supernatants are assayed. Simultaneous assay of MIF and LIF production in dilution of supernatants from adult lymphocytes showed higher LIF activity, whereas in cord lymphocytes MIF activity was greater than LIF activity. This further emphasizes the non-identity of MIF and LIF. These results indicate another abnormality of T cellular immunity in newborns not detected by T-cell enumeration or proliferative responses and parallels other defects in specialized T cell function such as cytotoxicity and immune interferon production.