The Effect Of Platelet On The Cytotoxicity Of Natural Killer Cells

Objective: To study the effect of platelet on the cytotoxicity of Natural Killer cells against K562 cells. Methods: K562 cells were coincubated with freshly isolated platelets from healthy person in vitro, adhesion of platelets to the K562 cells was observed by microscopy and the fraction of platelet adhesion to K562 cells was determined flow cytometry. As was done in the Heparin trials.NK cells were purified and expanded from peripheral blood mononucleal cell (PBMC). The rate of CD56+CD3-NK cells was determined flow cytometry. Platelets:K562 cells was 1000:k 250: k 0:1 respectively.MTT method, was used to access the effect of platelet on the lysis of K562 cells by Natural Killer cells purified and proliferated from PBMC. As was done in the Heparin trials.Results: K562 cells can adhere to platelets in vitro.The fraction of platelet adhesion to K562 cells amounted to (21.2+2.1) %.In the Heparin trials, the fraction was (12.4+1.6) % with significant difference (p<0.01) . The rate of purified CD56+CD3-NK cells amounted to 46.8%;through proliferation, the rate of CD56+CD3-NK cells amounted to 62.2% and proliferated 5.32 fold. Platelets can inhibit the cytotoxicity of NK cells against K562 cells in vitro. In compare to platelets to K562 cells 250:1,the killrate of NK cells against K562 cells in 1000:1 was lower with significant difference (p<0.01) . In compare to platelets deletion, the killrate of NK cells against K562 cells in 250:1 was lower with significant difference (p<0.01) . In the Heparin trials, the kill-rate of NK cells against K562 cells increased comparing to the control with significant difference (p<0.01) .Conclusions: Platelets can interact with K562 cells in vitro and inhibite the cytotoxicity of NK cells against K562 cells. Inhibition of platelets on the cytotoxicity of NK cells against K562 cells depended on the amount of platelets and can be impaired by Heparin.