Immunohistochemical localization of B7 costimulating molecules and major histocompatibility complex class II antigen in pulmonary sarcoidosis

Background: Alveolar macrophages (AM) of sarcoidosis have an en ha need cap acity to mediate antigen-induced T lymphocyte proliferation. To induce an e ffective immune response, antigen-presenting cells have to not only present antigenic peptide with MHC molecules to T lymphocytes, but also express B7 costimulating molecules. Objective: The purpose of this study was to inves tigate the expression of B7 and MHC molecules in lu ng tissues from patient s with sarcoidosis. Methods: We performed immunohistochemistry for B7-1, B7 -2 and MHC class II antigens using transbronchial lung biopsy specimens obt ained from patients with sarcoidosis and normal lung parenchyma obtained by lobectomy for solitary pulmonary nodule as controls. Results: B7-1, B7-2 a nd MHC class II antigen were expressed in epithelioid cells in granulomas i n 14(93.3%), 2 (13.3%) and 9 (60.0%) of 15 patients with sarcoidosis, respe ctively. These were also expressed in AM in 14(93.3%), 5 (33.3%) and 12(80. 0%) of 15 patients with sarcoidosis, respectively. The positivitiy of B7-1 was significantly higher than that of B7-2 in both epithelioid cells and AM in sarcoidosis (p < 0.01). Positive signals for B7-1, B7-2 and MHC class I I antigen were also found in AM in 9 (90%), 8 (80%) and 8 (80%) of 15 of co ntrols, respectively. However, the intensity of positive signals for B7-1, but not B7-2 or MHC class II antigen in AM was significantly increased in s arcoidosis compared to controls (p < 0.05). Conclusions: These results sugg ested that epithelioid cells in granulomas a nd AM from patients with sarco idosis had the capability to act as accessory cells and that the accessory function of these cells was shifted to B7-1 rather than B7-2 in sarcoidosis .