Molecular Analysis of Platelet-Immunocyte Interaction

我们研究了炎性细胞因子对血小板活化的影响。il - β和ifn - γ可增强凝血素处理过的血小板对单核细胞白血病细胞的粘附（U937），通过血小板介导的细胞凝集检测这种粘附。单克隆抗p -选择素抗体或EDTA均能抑制凝集，提示p -选择素介导了血小板对白血病细胞粘附增强。此外，在低浓度凝血酶存在的情况下，这些细胞因子也增加了血小板5-HT的释放。这些数据表明，血小板功能受细胞因子调节，活化的血小板参与炎症过程。接下来，我们研究了白细胞粘附于活化血小板的功能改变的可能性。我们使用人外周血单核细胞和中性粒细胞，并测量了这些细胞与血小板培养后产生的超氧阴离子。当使用凝血酶激活的血小板时，发现超氧阴离子产生水平明显升高。与静息血小板一起培养时，没有观察到这种增强。其增加与培养时间和血小板浓度有关。活化血小板制备的膜也能诱导超氧阴离子的产生，而活化血小板培养上清则没有。抗p -选择素抗体、抗sialyl- le ^X抗体或可溶性重组p -选择素-谷胱甘肽-s -转移酶（GST）融合蛋白可抑制增强的超氧阴离子产生。这些结果表明，活化的血小板通过p -选择素与白细胞的粘附是激活白细胞功能的关键步骤，并支持活化的血小板积极参与炎症过程的观点。

We have examined the effect of inflammatory cytokines on the platelet activation. IL-beta and IFN-gamma were found to enhance the adhesion of thrombin-treated platelets to moncytic leukemia cells(U937),when the adhesion was assayed by platelet-mediated cell agglutination. The agglutination was inhibited by a monoclonal anti-P-selectin antibody or EDTA,suggesting that the enhanced platelet adhesion to the leukemic cells was mediated by P-selectin. In addition,these cytokines also increased the release of 5-HT from platelets in the presence of a low concentration of thrombin. These data suggest that platelet functions are regulated by the cytokines and that activated platelets participate in inflammatory process. We next examined the possibility that leukocytes are functionally modified by their adhesion to activated platelets. We used human peripheral blood monocytes and neutrophils and measured superoxide anion generation by these cells cultured with platelets. The levels of superoxide anion production was found to be markedly elevated when thrombin-activated platelets were used.This enhancement was not observed when cultured with resting platelets. The increase depended on incubation time and platelet concentration. The membranes prepared from activated platelets also induced superoxide anion production,but the culture supernatant of activated platelets did not. The enhanced superoxide anion production was inhibited by anti-P-selectin antibody,anti-sialyl-Le^X antibody or a soluble recombinant P-selectin-glutathione-S-transferase(GST) fusion protein. These results indicate that the adhesion of activate dplatelets to the leukocytes through P-selectin was a crucial step for the activation of leukocyte function, and support the idea that activated platelets are actively involved in inflammation processes.