Ly-49D Transfected NK Cells Show Reduced Interleukin-10 Production in Response to H-2d and Increased Lytic Activity: Implication by Interaction Using Class I MHC Alloantigen+ Target Cells in Pregnancy
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PROBLEM: Mating of CBA/J (H-2k) with DBA/2 (H-2d) males leads to a high rate of spontaneous resorption (about 40%), which is not seen in other mating combinations, such as CBA/J X BALB/c. The activation of natural killer cells (NK cells) seems to be a key mechanism for the maternal-fetal intolerance in allogeneic pregnancy, and recurrent spontaneous abortion. The effect of expression of the NK cell activating receptor Ly49D recognizing BALB/c or DBA/2 class I MHC was investigated. METHOD OF STUDY: Intracellular interleukin (IL)-100 production was detected and target cell survival rates were calculated after 22 hr coincubation of rat NK cells transfected, or not. with a murine Ly49D receptor, with either male BALB/c or male DBA/2 splenocytes, by using flow cytometry. RESULTS: Ly49D negative rat NK cells produced 13.7% more IL-10 than Ly49D positive rat NK cells, and more splenocytes were killed by Ly49D transfected rat NK cells (survival rate 2.45%) than by Ly49D negative rat NK cells (survival rate 4.36%). CONCLUSION: After physiological stimulation with BALB/c or DBA/2 splenocytes, rat NK cells are able to synthesize IL-10. Recognition of mouse splenocyte major histocompatibility complex (MHC) by Ly49D mice receptor decreased IL-10 production. The observed increase in killing activity might be a result of this phenomenon. NK cell activation via the Ly49D receptor might play an important role in pregnancy failure, but cannot explain why CBA/J X DBA/2 matings are abortion prone, and CBA/J X BALB/c matings are abortion resistant.
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