Analysis of T helper and antigen-presenting cell functions in cord blood and peripheral blood leukocytes from healthy children of different ages.

The development of antigen-specific functional T lymphocyte immunity in infants and children is an area of immunology that needs elucidation. Leukocytes from cord blood (CBL) and from PBL of children of different ages who were in the hospital for minor surgical procedures were compared with PBL from healthy adults for their ability to generate T helper cell (Th) responses assessed by in vitro proliferation and IL-2 production after stimulation with: influenza A virus (FLU); tetanus toxoid (TET); adult allogeneic PBL that were either undepleted (ALLO) or depleted of adherent antigen presenting cells (ALLONW); and PHA. CBL generated Th responses to ALLONW, ALLO, and PHA, but not to FLU or TET. PBL from infants between 6 and 13 mo of age responded to ALLO and PHA; none responded to FLU or ALLONW, and two of four responded weakly to TET. PBL from children between 13 and 26 mo of age responded to all stimuli except FLU, to which only one child responded marginally. PBL from children older than 36 mo responded to all stimuli at levels comparable to those of PBL from adults. The use of undepleted and adherent cell-depleted CBL and PBL from children of different ages as allogeneic stimulators of responses generated by PBL from adults indicated that the antigen presenting function of CBL and PBL from children 13 mo or older are sufficiently developed to present alloantigen, whereas PBL from children younger than 13 mo are not. Therefore, our results indicate that age-dependent differences exist in both T helper and antigen-presenting functions of CBL and PBL from children of different ages. Surprisingly, CBL appear to be more efficient in antigen-presenting function than PBL from children younger than 13 mo. These findings are important for establishing developmental parameters of T helper cell immunity relevant for pediatric infection and transplantation in infants and children.