Immunohistochemical Localization of B7 Costimulating Molecules and Major Histocompatibility Complex Class II Antigen in Pulmonary Sarcoidosis

Abstract

Background: Alveolar macrophages (AM) of sarcoidosis have an enhanced capacity to mediate antigen-induced T lymphocyte proliferation. To induce an effective 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 investigate the expression of B7 and MHC molecules in lung tissues from patients with sarcoidosis. Methods: We performed immunohistochemistry for B7-1, B7-2 and MHC class II antigens using transbronchial lung biopsy specimens obtained from patients with sarcoidosis and normal lung parenchyma obtained by lobectomy for solitary pulmonary nodule as controls. Results: B7-1, B7-2 and MHC class II antigen were expressed in epithelioid cells in granulomas in 14 (93.3%), 2 (13.3%) and 9 (60.0%) of 15 patients with sarcoidosis, respectively. 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 II antigen were also found in AM in 9 (90%), 8 (80%) and 8 (80%) of 15 of controls, 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 sarcoidosis compared to controls (p < 0.05). Conclusions: These results suggested that epithelioid cells in granulomas and AM from patients with sarcoidosis 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.