Research Abstract |
1.Direct precursors of NK-T cells were identified in ZAP-70-/-mice and RAG-/-mice. These were NK1.1^+,TCR^-and exhibited a unique phenotype similar to NK cells. Upon stimulation with PMA +ionomycin, these precursors differentiated into NK-T cells in a neonatal thymic organ culture. 2.A normal population of NK-T cells were found in 2C transgenic mice with TCR specific for MHC class I. In the negative MHC background(H-2^d) the major population of NK-T cells were CD4,8 double negative, whereas in the positive background(H-2^b) the major NK-T cells were CD8 single positive. These NK-T cells produced a large amount of IFN-γ but not IL-4 upon stimulation with anti-CD3 mAb in vivo. No NK-T cells were generated in the neutral background(H-2^k). CD1 molecules appeared not to be involved in the selection of NK-T cells. These findings demonstrate that a certain population of NK-T cells has been developed under the influence of MHC but not CD1 molecules. 3.Proliferation of NK-T cells was detected in syngeneic mixed lymphocyte response(SMLR) where purified dendritic cells were stimulators. The antigen system that NK-T cells recongnize in the SMLR is now under investigation. 4.Age-related decrease in the proportion of NK-T cells was found in New Zealand strains of mice, autoimmune prone a strains, but not in another autoimmune prone strain, 1pr mice. It appeared that these decreases were associated with the high complement sensitivity of NK-T cells. 5.Using aly/aly mice it shown that thymic medullary epithelial cells were indispensable to generation of NK-T cells.
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