The role of thymus-dependent T cells in hexachlorobenzene-induced inflammatory skin and lung lesions

Hexachlorobenzene-induced eosinophilic and granulomatous lung inflammation is associated with in vivo airways hyperresponsiveness in the Brown Norway rat

We investigated whether the eosinophilic and granulomatous lung pathology that develops in Brown Norway (BN/SsNOlaHsd) rats upon feeding hexachlorobenzene (HCB) is associated with nonspecific in vivo airways hyperresponsiveness (AHR) to methacholine. To this end, female BN/SsNOlaHsd rats were exposed to diets with no supplementation or diets supplemented with 450 mg HCB per kg feed. On days 7 or 21 of exposure in vivo airways hyperresponsiveness to increasing concentrations of methacholine was assessed both by whole body plethysmography and by visual scoring. In addition, lungs were lavaged to count and differentiate lavage cells, and skin and lungs were processed for histology. Lungs of the control rats showed some scattered microgranulomas and by 3 weeks of control diet some rats showed rather extensive granuloma formation and perivascular and peribronchiolar infiltration of eosinophils, as well as increased responsiveness to methacholine. Oral exposure to HCB for 7 days caused a moderate perivasculitis, but no increase of total serum IgE levels and no AHR to methacholine was found. Prolonged HCB exposure for 21 days resulted in severe and extensive eosinophilic and granulomatous lung inflammation, a threefold increase of total serum IgE levels, and marked cholinergic AHR in all rats. Correlation analysis revealed a significant relation between the AHR and lung inflammation, as judged by granuloma formation and increased numbers of eosinophilic granulocytes in the lung interstitium, particularly around the bronchi and bronchioli. No correlation was observed between serum IgE levels and AHR. Data suggest that HCB induces AHR by stimulating eosinophilic lung inflammation and that the preexistent microgranulomas may predispose to development of the HCB-induced lung pathology.