B lymphocyte accumulations in human pulmonary sarcoidosis

Abstract

Background Although cell mediated immunity is primarily thought to mediate the pathogenesis of sarcoidosis, the prese1ie immune complexes an complement suggests that processes of humoral immunity may contribute to immunopatholoogy in sarcold lesions. To test this hypothesis, the-distribution of B lymphocytes in paraffin embedded sarcoid lesions in mediastinal lymph nodes and open lung biopsy specimens was investigated. Methods Paraffin sections from eight open lung and 21 lymph node biopsies from sarcoid patients and five normal and five tuberculosls lymph nodes from patients-with tuberculosis were stained with a panel of monoclonal antibodies by means of avidin/biotin enhanced immunocytochemistry. Results Immunohistochemical analysis of the 29 biopsy specimens from the sarcoid patients revealed large numbers of B cells in the intergranulomatous regions. Further investigations in the open lung biopsy specimens indicated that these B cells were often organised circular or oval shaped aggregates with no germinal cenfre morphology, in which a few CD45RO memory T lymphocytes were scattered. The B cells were polyclonal, and a few plasma cells (IgM+, IgA +, IgG + ) were identified. Conclusions The finding of large numbers ofB lymphocytes in sarcoid pulmonary lesions is in contrast to ronchoalveolar lavage studies, which have demonstrated proportions of 5% or less of B cells as a total of all immune cells, and therefore indicates that bronchoalveolar lavage mayne immune cells of lung interstitial tissue in pulmonary sarcoidosis. The B cells at these sites areitiipossible oriin ofsme of the humoral changes in the serum and lesions of sarcoid patients. They may also influence=the pat=hodgeniesisoof trhecer by presenting antigen(s) and forming immune complexes at sites of disease activity.