RESULTS: 1) The level of miR-15a/16 was statistical difference between survival group non-survival group in the 1, 7, 10 and 15 days. White blood cells were sorted into monocytes, lymphocytes and neutrophils and miR-223 was significantly high in lymphocyte. 2) The expression of miR-223/15a/16 was positively correlated with lymphocytes and lymphocyte apoptosis. Cell number ratio of G1 phase and S phase reduced significantly in Agomir 223 group compared to Antagomir 223 group, indicating miR-223 causes cell cycle arrest. 3) We cultured whole blood of septic patients and transfected with Antagomir-223 and Antagomir NC. The early apoptosis proportion of lymphocyte was significantly lower in Antagomir-223 group than control. 4) FAS stimulating antibody was used to induce apoptosis. Result of MTT tests showed that the OD value of agomir 15a/16 groups are significantly lower than control, the OD value of antagomir 15a/16 groups are significantly higher than control. miR-15a/16 were proved to inhibit cell proliferation. Flow cytometry showed the proportion of apoptosis in agomir 15a/16 groups are significantly higher than the control. 5) Western blot showed phosphorylation FOXO1 was decreased in Agomir 15a/16 groups and increased in antagomir 15A/16 groups, indicating miR-15a/16 increases the non-phosphorylation form of FOXO1, which actives FOXO1 and its downstream apoptosis-related molecules.