Neonatal (cord blood) T cells can competently raise type 1 and 2 immune responses upon polyclonal activation

In the neonate, cellular immunity has generally been hypothesized as being incompetent. Accumulating evidence from several recent studies, together wi th our present report, contradicts this hypothesis. T-helper cell and T cyt otoxic type 1 and 2 (Th1/Th2 and Tc1/Tc2, respectively) cytokine responses to polyclonal T cell. receptor (TCR) activation were assessed in medium-ter m cultures of human cord blood T cells using intracellular cytokine stainin g, which could measure the frequencies of cytokine-producing cells. In this study, we examined the responses of cord blood CD4(+) and CD8(+) T cells i n regard to the production of interferon (IFN)-gamma and interleukin (HL)-4 and compared the responses with those obtained from T cells of healthy adu lts. We found that the responses in cord blood T cells activated with TCR s timulation were comparable to those of their adult counterparts. Moreover, the Th/Tc cells that developed in cord blood were as competent as adult cel ls for both IFN-gamma and IL-4 secretion. In addition, IL-12 production, wh ich is critical for both Th1 and Tc1 responses, was equally comparable in t he two groups. The production of two major cross-regulatory cytokines, tumo r necrosis factor-alpha and IL-10, was similarly comparable and not signifi cantly different between the two groups. Taken together, these results indi cate that, though naive, the neonatal T cell is competent to respond to TCR -mediated stimulation and to produce both type 1 and type 2 cytokines. (C) 2000 Academic Press.