Abstract
The maturity of the newborn's immune system was assessed by measuring proliferative responses and interferon production of isolated mononuclear cells from cord blood ( N = 19), newborns 1 to 7 days of age ( N = 19), and adult controls ( N = 18). Ficoll-Hypaque-separated mononuclear cells were stimulated with phytohemagglutinin (PHA), allogeneic leukocytes in a mixed leukocyte culture (MLC), or Newcastle disease virus (NDV), pulsed with thymidine after 3 to 7 days in culture, and thymidine incorporation into DNA measured and used to calculate a proliferative index. The supernatants were h-arvested at optimal times for assay of classical and immune interferon (IF) production. IF was assessed by a microtiter assay using human diploid cells after encephalomyocarditis virus challenge. The proliferative responses of cord and newborn cells were equivalent or greater than those of adult controls. PHA-induced immune IF was produced in only 1 of 19 cord bloods and 3 of 19 newborns, whereas immune IF was produced in all adults (225 ± 2 units). No IF was produced in MLC in newborns, cords, or adults. NDV-induced classical IF was produced in normal amounts by newborn (373 ± 2IU), cord (457 ± 2IU), and adult cells (170 ± 3IU). These results indicate an abnormality of cellular immunity in newborns not detected by T-cell numbers or proliferative responses and parallels similar defects in T-cell-mediated cytotoxicity, another specialized T-cell function. These results suggest a possible mechanism for viral infection in newborns with concomitant bacterial infections and in patients undergoing graft-versus-host reactions.
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