Inflammatory, anti-inflammatory and regulatory cytokines in relatively healthy lung tissue as an essential part of the local immune system

Background. The innate and adaptive immune systems in lungs are maintained not only by immune cells but also by non-immune tissue structures, locally providing wide intercellular communication networks and regulating the local tissue immune response. Aims. The aim of this study was to determine the appearance and distribution of inflammatory, anti-inflammatory and regulatory cytokines in relatively healthy lung tissue samples. Material and Methods. We evaluated lung tissue specimens obtained from 49 patients aged 9–95 years in relatively healthy study subjects. Tissue samples were examined by hematoxylin and eosin staining. Interleukin-1 (IL-1), interleu-kin-4 (IL-4), interleukin-6 (IL-6), interleukin-7 (IL-7), and interleukin-10 (IL-10) were detected by an immunohistochemistry (IMH) method. The number of positive structures was counted semiquantitatively by microscopy. Non-parametric tests were used to analyse the data. Results. IL-1-positive cells were mostly found in the bronchial cartilage and alveolar epithelium. Immunoreactive lung macrophages were also found. The numbers of IL-4, IL-6, IL-7, and IL-10 containing cells were also found in the bronchial epithelium (in addition to those previously listed). The number of positive structures varied from occasional to moderate, but was graded higher in cartilage. Overall, fewer IL-1-positive cells and more IL-10-positive cells were found. Almost no positive structures for all examined cytokines were found in connective tissue and bronchial glands. Conclusions. Relatively healthy lung tissue exhibits anti-inflammatory response patterns. The cytokine distribution and appearance suggest persistent stimulation of cytokine expression in lung tissue and indicate the presence of local regulatory and modulating patterns. The pronounced cytokine distribution in bronchial cartilage suggests the involvement of a compensatory local immune response in the supporting tissue.