Allergy and experimental chronic broncho-pneumopathy

House dust is a mixture of specific and non-specific stimulating factors. More particularly it contains a wide range of irritating factors, antigens, responsible for the production of immediate and delayed allergic reactions, moulds, microbes, etc. It may therefore be understood that inhalation of house dust induces in the respiratory tract of treated rats various reactive pictures. These pictures are, however, dominated by immuno-allergic reactions. Immuno-allergic reactions are manifested by the dominant increase in plasma cells and lymphocytes. This increase generally occurs in the vicinity of connective tissue macrophages containing numerous dust granules, as if macrophagic digestion formed more active antigens from the dust. Sometimes in the proximity of these plasma cell aggregates, mast cells in the degranulation phase are observed. The release of histamine, serotonin, etc. which occurs with mast cell degranulation produces the intense tissue edema which is observed in these areas. An infiltration with eosinophils is also observed here probably drawn to the site on account of their protective, enzymatic, antihistaminic action. The morphological picture thus indicates the co-existence of two allergic reactive movements: one of the immediate type, the other of the delayed type linked to specific allergens of the mixture of antigens present in house dust. The stimulus of the inhalation of house dust also includes the possible action of microbes, irritants, etc. which produce regressive changes in the tissue, attract polymorphs and stimulate the proliferation of fibroblasts so that more or less wide area of tissue undergo a fibrous transformation. Such changes may be found in the pulmonary parenchyma as well as in the bronchial mucosa. The concordance of these findings with those of chronic bronchitis in man appear sufficiently important to attribute, a predominantly allergic pathogenesis to both pathological conditions. This concept obviously does not exclude other etiopathogenetic factors which under certain environmental or constitutional conditions, may in various degrees be also included in the overall picture of respiratory tissue reactivity.