The effect of regulatory dendritic cells of spleen on inflammatory response and outcome in mice with burn injury

Objective To observe the effect of regulatory dendritic cells (DCregs) on burn injury induced proinflammatory cytokine production and mortality rate after a single intraperitoneal injection of CD11clowCD45RBhigh DCs to injured mice. Methods DCregs were isolated and purified from spleen of 100 normal BALB/c mice to procure CD11clowCD45RBhigh DCs by MiniMACS. Mice were subjected to a 15% total body surface area (TBSA) burn injury on the back. Twenty mice were used, and splenic DCregs (1×105/ml, 5×105/ml, 10×105/ml) were given to them to investigate the protective effect of DCregs against lethality at postburn hours (PBH) 48, and to decide the optimal dosage of intervention. Another group of 70 mice were used, and they were divided into normal control group (n=7), sham burn injury group (n= 21), burn injury group (n = 21), and DCregs treatment group (n = 21). The mice in burn injury group received intraperitoncally 1 ml of Ringer solution for resuscitation. 10×105/ml of CD11clowCD45RBhigh DCs were added to lactated Ringer solution for intraperitoneal injection in DCregs treatment group. Seven animals of each group were sacrificed at PBH 12, 24 and 48, respectively, and blood samples were collected aseptically for measurement of cytokine levels in plasma and phenotype expressions on DCs by flow cytometry. Results Treatment with 10×105/ml DCregs showed a significant decrease in mortality rate compared with burn injured mice and burn injured mice given lower doses of DCregs (1×105/ml, 5×105/ml DCregs, 0% vs. 80%, 80% and 60%, all P＜0. 01). A single intraperitoneal injection of 10×105/ml DCregs to burn injury mice showed a significant decrease in plasma interleukin-6 (IL-6, ng/L: 98. 76 ±10.02, 57. 83 ±6. 83, 13.29 ±1.07) compared with burn injury mice (156.32 ± 12. 85, 84. 50 ±9. 29,23.04±2. 53) at PBH 12, 24 and 48 (all P＜0. 01). Similarly, in 10×105/ml DCregs treatment group,plasma macrophage chemoattractant protein-1 (MCP-1) levels (ng/L: 102.79 ±9. 88, 42. 56 ±5. 90,12. 96±1. 34) were markedly lower than those in burn injury group (168. 23±23. 85, 83. 39±8. 41, 42. 92±4. 96) at PBH 12, 24 and 48 (all P＜0. 01). A single intraperitoneal injection of 10×105/ml DCregs to burn injury mice showed significant reduction in plasma tumor necrosis factor-α (TNF-α) levels (ng/L: 16. 84±1.92, 16. 62±1.28, 10. 26±1. 10) compared with burn injury mice (24. 16±4. 93, 24.25±4. 01, 17. 91±1.82) at PBH 12, 24 and 48 (all P＜0. 01). Conclusion DCregs may effectively improve the outcome of mice with severe burn injury through a single intraperitoneal injection of DCregs accompanied by lowering excessive inflammatory reaction. Key words: Regulatory dendritic cell;  Burn injury;  Sepsis;  Inflammatory response;  Cytokine