Although elevated blood or sputum eosinophils are present in many patients with chronic obstructive pulmonary disease (COPD), uncertainties remain regarding the anatomical distribution pattern of lung-infiltrating eosinophils. Basophils have remained virtually unexplored in COPD. This study mapped tissue-infiltrating eosinophils, basophils, and eosinophil-promoting immune mechanisms in COPD-affected lungs.Surgical lung tissue and biopsies from major anatomical compartments were obtained from COPD patients with severity grades GOLD I-IV; never-smokers/smokers served as controls. Automated immunohistochemistry and hybridisation identified immune cells, the type 2 immunity marker GATA3, and eotaxins (CCL11, CCL24).Eosinophils and basophils were present in all anatomical compartments of COPD-affected lungs and increased significantly in very severe COPD. The eosinophilia was strikingly patchy, and focal eosinophil-rich microenvironments were spatially linked with GATA3 cells, including Th lymphocytes and type 2 innate lymphoid cells. A similarly localised and IL-33/ST2-dependent eosinophilia was demonstrated in influenza-infected mice. Both mice and patients displayed spatially confined eotaxin signatures with CCL11 fibroblasts and CCL24 macrophages.In addition to identifying tissue basophilia as a novel feature of advanced COPD, the identification of spatially confined eosinophil-rich type 2 microenvironments represents a novel type of heterogeneity in the immunopathology of COPD that will likely have implications for personalised treatment.
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