[Immunohistochemical study of T cell subsets in lung tissue and in BALF of patients with farmer's lung disease].

The purpose of this study was to ascertain the immunological abnormality of hypersensitivity pneumonitis. The relationship between T cell subsets of lymphocytes in transbronchial lung biopsy (TBLB) specimens and in bronchoalveolar lavage fluid (BALF) were studied in 3 cases of farmer's lung disease (FLD). The lung specimens were examined by immunoperoxidase staining (ABC method) and the cells in BALF by the immunofluorescence method on the flowcytometry. All cases of FLD were diagnosed according to the following criteria: 1) history of exposure to FLD antigen, 2) clinical symptoms (cough, fever, breathlessness), 3) radiologic feature (diffuse small nodular pattern) and functional pattern of interstitial lung disease and 4) evidence of antibodies against Micropolyspora faeni. Histologically, granulomatous interstitial pneumonitis was revealed in all cases. Immunohistochemically, the number of positive lymphocytes was as follows: for Leu 4 (pan T cell) 8.6 cells/15.6 x 10(-3) mm2; Leu 3a (helper/inducer T cell) 5.1 cells; Leu 2a(suppressor/cytotoxic T cell) 1.2 cells on average, respectively. The Leu 3a+ cells were larger in number than the Leu 2a+ cells and the Leu 3a+/Leu 2a+ ratio was 4.76. In the BALF, the percentage of OKT3+ cells (pan T cell) was increased. The percentage of OKT4+ cells (helper/inducer T cell) was higher than that of OKT8+ cells (suppressor/cytotoxic T cell). The OKT4+/OKT8+ ratio was 6.65 in the BALF. The result of this study revealed the close relationship between the numerical distribution of T cell subsets in the lung tissue and in the BALF. It is suggested that the immuno-reaction in the lung tissue of patients with FLD is a type of helper-T cell alveolitis.