Cigarette smoke-induced pulmonary inflammation is attenuated in CD69-deficient mice

Cluster of differentiation 69 (CD69) has been identified as a lymphocyte early activation marker, and recent studies have indicated that CD69 mediates intracellular signals and plays an important role in various inflammatory diseases. Cigarette smoke (CS) is a strong proinflammatory stimulus that induces the release of proinflammatory mediators by recruiting macrophages and neutrophils into the lung tissue, and is one of the main risk factors for a number of chronic diseases. However, the potential role of CD69 in CS-induced pulmonary inflammation has not been determined. To address to this question, CD69-deficient (KO) and wild-type (WT) mice were subjected to CS-induced acute pulmonary inflammation. After the exposure with CS, the expression of CD69 in the lung of WT mice was significantly induced, it was predominantly observed in macrophages. In conjunction with this phenomenon, neutrophil and macrophage cell counts, and expression of several cytokines were significantly higher in the bronchoalveolar lavage fluid (BALF) of CS-exposed WT mice compared with air-exposed WT mice. Likewise, the CS-induced accumulation of inflammatory cells and cytokines expression were significantly lower in CD69-KO mice than in WT mice. These results suggest that CD69 on macrophages is involved in CS-induced acute pulmonary inflammation.