Immune competence of newborn lymphocytes

The immune competency of peripheral blood (cord) lymphocytes of newborn infants has been investigated by a battery of assays in vitro. Number of T cells was enumerated by E-rosette formation and a cytotoxicity assay by using an anti-human-thymocyte antiserum. Lymphokine production as an indicator of T cell function was evaluated by leukocyte migration inhibition factor production following stimulation with various mitogens, and "viral" and "immune" interferon production in response to stimulation with polyriboinosinic -cytidilic acid and phytohemagglutinin, respectively. Ability to respond to mitogens was also tested by means of 3H-thymidine uptake into DNA, and by measuring the early synthesis of protein by lymphocytes by means of 3H-leucine uptake. Lymphocyte cyclic adenosine monophosphate levels in resting cells and after trypsin treatment was also used as a test of cellular competency. Total B cells was evaluated by EAC-rosette formation, and class specific surface membrane immunoglobulin-bearing cells were assayed by the peroxidase immunoenzymatic method. Normal children and adults served as controls. The results indicated that no significant differences in immune competency could be shown between newborns and older people except for lymphocyte cyclic adenosine monophosphate levels which were lower in the newborns, both in resting and in stimulated cells. The relationship between this latter finding and the immune status is as yet not clear. It is concluded that neonatal lymphocytes are essentially immunocompetent, with the expression of their immune capabilities in vivo becoming apparent only after encounter with environmental antigenic stimuli.