Objective To investigate effect of thymus pentapeptide injection on immune function and postoperative infection in patients with open fractures of lower extremity.

Methods The clinical data of 60 patients with Gustilo-Anderson type Ⅲ open fracture of lower extremity admitted to the emergency intensive care unit of Shanghai Jiao Tong University Affiliated to Sixth People′s Hospital were collected. The patients were divided into infected group (n=8) and non-infected group (n=52) according to whether postoperative infection occurred or not, and were divided into experimental group (n=42) and control group (n=18) according to whether they received treatment of injection of thymopentin or not. The control group received routine treatment, while the experimental group received intramuscular injection of thymopentin for 20 mg once a day for 7 days on the basis of routine treatment. The levels of lymphocytes and subsets were compared between the infected group and the non-infected group. The changes of immune function indexes and the occurrence of postoperative infection were observed between the experimental group and the control group.

Results Of 60 patients with lower extremity open fracture, 8 patients developed wound infection after operation. A total of 17 strains were isolated, including 5 strains of Klebsiella pneumoniae, 4 strains of Pseudomonas aeruginosa, 3 strains of Acinetobacter baumannii, 2 strains of Enterococcus faecium, 1 strain of Staphylococcus aureus, 1 strain of Escherichia coli and 1 strain of Enterobacter cloacae. On the 7th day after injury, the proportions of CD3 and CD4 cells in the infected group were lower than those in the non-infected group (P < 0.05). The infection rate of the experimental group was 9.52%, which was lower than 22.22% of the control group, but the difference was not statistically significant (P>0.05). On the 1st day after injury, the proportions of CD3 and CD4 cells in the experimental group were lower than those in the control group, while the proportion of CD19 cells was higher than that in the control group (P < 0.05). The proportions of CD3 cells, CD4 cells and ratio of CD4 to CD8 of the control group on the 7th day after injury were lower than those on the 1st day after injury (P < 0.05). In the experimental group, the proportions of CD3, CD4 and CD8 cells increased on the 7th day after injury, while the proportion of NK and CD19 cells decreased (P < 0.05).

Conclusion Immunosuppression occurs after severe trauma. The proportions of CD3 and CD4 cells in infected patients decrease significantly. Although thymopentin injection can′t significantly reduce the postoperative infection rate of patients with open lower limb fractures, it can increase the proportions of CD3 and CD4 cells, and effectively improve the immune function of patients after injury.