Modulation of CD4+CD25+CD127 dim/-regulatory T cells by interleukin-35 in the pathogenesis of vent- ilator-associated pneumonia / 中华微生物学和免疫学杂志

ABSTRACT

Objective To investigate the changes in CD4+CD25+CD127 dim/- regulatory T cells ( Tregs) and interleukin ( IL)-35 in peripheral blood and bronchoalveolar lavage fluid ( BALF) samples from patients with ventilator-associated pneumonia ( VAP) . Methods A total of 23 patients with VAP and 11 normal controls ( NCs) were enrolled in this study. Peripheral blood mononuclear cells, serum and BALF samples were isolated and collected. Levels of IL-35 were measured by enzyme linked-immunosorbent assay. Percentages of CD4+CD25+CD127dim/-Tregs were measured by flow cytometry. CD4+CD25+CD127dim/-Tregs in BALF samples were isolated and purified, which were then stimulated with recombinant human IL-35 and co-cultured with autologous CD4+CD25-T cells. Cells and supernatants were harvested for analysis of cell proliferation and cytokine secretion. Results No significant difference in peripheral Tregs and serum IL-35 was found between patients with VAP and NCs. The percentages of Tregs and the levels of IL-35 in BALF samples collected from infectious sites were remarkably higher than those collected from non-infectious sites in patients with VAP. Moreover, there was a positive correlation between Tregs and IL-35 in BALF ( r=0. 441, P=0. 035). Tregs and IL-35 in BALF samples as well as Treg-secreted IL-35 were significantly re-duced in patients who had good response to therapy. However, no significant change in these parameters was observed in patients who had poor response to therapy. Besides, suppression of cell proliferation and IL-10 secretion that were related to Tregs were inhibited in patients whose condition was improved as compared with those in patients who had no response to therapy. Stimulation with recombinant human IL-35 enhanced the immunosuppressive function of purified Tregs that were separated from BALF of treatment-na?ve patients with VAP, which was mainly marked by suppressed cell proliferation, increased secretion of inhibitory cytokines (IL-35 and IL-10), and decreased secretion of proinflammatory cytokines (IFN-γ and TNF-α). However, IL-35 had little effect on the activities of Tregs that were separated from patients with VAP who responded to therapy. Conclusion Both IL-35 and Tregs are increased in BALF of patients with VAP and IL-35 en-hances the immunosuppressive function of Tregs, which indicates that IL-35-mediated modulation of Tregs might take part in the pathogenesis of VAP.