T cell receptor heterodimer (alpha beta/gamma delta) expressions in diffuse panbronchiolitis

Abstract

Several reports have indicated that T cells bearing gamma delta T cell receptor (TCR) are major effector cells in mucosal immunity of the murine intestinal tract. In humans, abnormal distribution of gamma delta + T cells has also been found in inflammatory bowel diseases. We studied TCR heterodimer expressions in lymphocytes infiltrating the peripheral airways in patients with diffuse panbronchiolitis (DPB), because DPB is histologically characterized by chronic inflammation in bronchioles and could be a model for investigation of the significance of gamma delta + T cells in persistent inflammation of the human respiratory tract. Open lung biopsy specimens were obtained from 7 patients and peripheral blood lymphocytes (PBL) from 9 patients. Immunohistochemically, we detected alpha beta and gamma delta TCR by avidin-biotin complex immunoperoxidase method, utilizing BMA 031 and TCR delta 1 monoclonal antibody, respectively, PBL were analyzed by flow cytometry. Histological analysis revealed that DPB lesions mainly involved the bronchiolar walls with marked infiltration of small round cells. Many T cells were distributed in the submucosal area, although few T cells infiltrated the epithelium. Most of the T cells in the bronchioles expressed alpha beta TCR (98.7%), whereas only 1.3% expressed gamma delta TCR. There was no significant difference in the percentage of gamma delta + T cells in PBL between DPB and age- and sex-matched controls (6.7% vs. 9.1%). These results suggest that the increase of T cells bearing alpha beta TCR played a major role. However, the possibility that the decrease of T cells bearing gamma delta TCR caused reduced mucosal defense against external antigens, leading to persistent inflammation of the lower respiratory tracts in DPB, is not excluded.