Evidence for the ontogenic precedence of suppressor T cell functions in the human neonate

The study was undertaken to elucidate some functional characteristics of T cell subsets in human cord blood. A comparison of the cellular interactions involved in the in vitro regulation of pokeweed (PWM) vs. Epstein‐Barr virus (EBV)‐driven B cell differentiation was done in vitro in short‐term cultures of lymphocytes from newborns or adults. T cell subsets were isolated using the monoclonal antibodies OKT4+ and OKT8+. OKT4+ but not OKT8+ T lymphocytes from adults as well as neonates suppressed EBV‐induced immunoglobulin (Ig) secretion of B lymphocytes from adults. This inhibition was mediated through gamma‐type interferon (IFN‐γ). B cells from newborns were not inhibitable by OKT4+ lymphocytes as a result of their insensitivity to IFN‐γ. Helper activity for PWM‐induced Ig secretion was exclusively contained within the OKT4+ population from adult T cell donors. This function was normally not detectable in any of the neonatal T cell subsets. OKT8+ cells from both adults and neonates suppressed PWM‐induced Ig secretion, but required the collaboration with cells within the OKT4+ population. The suppressor activity in the PWM system was not IFN‐γ‐mediated. Thus, suppressor functions for EBV‐vs. PWM‐induced Ig synthesis were mediated through different pathways. There was no evidence of a unique suppressor system in the newborn. In the neonate, suppressor T cell activities are developed before T helper functions, a circumstance for which there is good evolutionary reason.