[Ontogenic development of human natural killer (NK) cells and lymphokine activated killer (LAK) cells]

Ontogenic development of human NK cells and LAK cells was evaluated in fetuses in spontaneous abortion, premature infants and full term infants. Additionally, we examined the effect of the production of interleukin-2(IL-2) of cord blood lymphocytes on PHA stimulation. The results were as follows. The NK activity of full term infants was significantly lower than that of adults. But augmented NK activity by recombinant IL-2 (20 U/ml) of term infants was the same as adult levels. However, before 32 weeks gestation, both NK activity and augmented NK activity by recombinant IL-2 were lower than that in full term infants. Using two color flow cytometry, after 16 weeks gestation, the percentage of Leu7- Leu11+ cells was almost equal to the adult level, but only a small number of Leu7+ Leu11+ and Leu7+ Leu11- lymphocytes was noted in premature infants and full term infants. LAK activity was evaluated in fetuses. Fetus that had advanced to 19 weeks of gestation had sufficient LAK activity. After 16 weeks gestation, fetal lymphocytes had good IL-2 production. Therefore in infants, LAK cell can play an important role in immunological surveillance against neoplastic tumor.