| Budget Amount *help |
¥6,700,000 (Direct Cost: ¥6,700,000)
Fiscal Year 1986: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1985: ¥4,900,000 (Direct Cost: ¥4,900,000)
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| Research Abstract |
1. Peripheral blood mononuclear cells(MNC) from fetuses of estimated gestational age of 20 wk lacked NK cell activity against K 562 target cells even after 18 hr-treatment with interferon- <gamma> (IFN- <gamma> ). Low, but significant levels of basal and IFN- <gamma> -inducible NK cell activity were observed in premature infants of 27-wk-gestation, with a progressive increase of these activities during the last trimester of pregnancy. Contrary to IFN- <gamma> , interleukin-2(IL-2) could induce a marked NK cell activity even in MNC from fetuses of 20-wk-gestational age and in Leu- <11^-> cell population of cord MNC, each of them lacked both basal and IFN- <gamma> -inducible NK cell activity. These ontogenic development and lymphokine responsiveness of human NK cell activity indicated that putative precursors of NK effector cells might be divided into IFN- <gamma> -responsive, more mature inactive forms of NK cells and into putative NK progenitors responding well to IL-2, but not to IFN- <gamma> , which might appear at an earlier stage of fetal development than IFN- <gamma> -responsive ones.
2. In cord blood, Leu- <11^+> cells were comparable in number with adult controls, but Leu- <7^+> cells were very meager. Preliminary studies indicated that low levels of Leu- <7^+> cells in cord MNC might be responsible for the poor ability of cord blood in their anti-CD3-inducible cytotoxicity.
3. Dissociated production of IL-2 and IFN- <gamma> , ample production of IL-2 and poor secretion of IFN- <gamma> , on PHA stimulation is a characteristic of cord MNC. In this report, some experimental data suggesting that IFN- <gamma> production by PHA-stimulated cord MNC to be down-regulated by preferential activation of suppressor precursors against IFN- <gamma> production, were presented. These PHA-inducible suppressor precursors in cord MNC expressed in large T4 helper phenotype and were radiosensitive in nature.
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