Early Recruitment of IL-10-Producing B Cells Into Alveoli Improved the Resolution of Acute Lung Injury.

BACKGROUND Acute lung injury (ALI) is characterized by rapid induction of inflammation at the alveolar-capillary membrane, and immunosuppressive mechanisms were shown to contribute to its resolution. Despite the central role of lymphocytes in initiating and mediating an inflammatory response, their influx dynamics in ALI has not been examined. METHODS We collected mini-BAL samples from the lung of ALI patients over a maximum period of 7 days, and examined the lymphocyte composition. RESULTS CD3+CD4+IFN-gamma+ Th1 cells were detected early on in all patients examined, while IL-10-producing B cells and CD3+CD4+CD25hiFoxp3+ Treg cells appeared later. Interestingly, IL-10-producing B cells appeared earlier than Tregs in most subjects, which possibly exerted anti-inflammatory function before Tregs. We then found that in patients with earlier recruitment of IL-10-producing B cells, the magnitude of Th1 inflammation decreased significantly over time, which was not observed in patients with later recruitment of IL-10-producing B cells. Furthermore, early IL-10-producing B cell recruiters also had significantly earlier recruitment of Tregs and better survival than late IL-10-producing B cell recruiters. CONCLUSION This study provided data on the alveolar infiltration of lymphocytes during ALI, which suggested an inhibitory role of IL-10-producing B cells in ALI and emphasized the importance of controlling inflammation during the initial stage of ALI.