Deficiency of immune interferon production by leukocytes of normal newborns

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.