Clonal analysis of lung and blood T cells in patients with sarcoidosis

Abstract

Background - Sarcoidosis is a disease characterised by clinical "anergy" to delayed type hypersensitivity antigens and the formation of non-caseating granulomas, which frequently manifests in the lungs as a T lymphocyte/mononuclear cell alveolitis. Although there is an increased proportion of T cells in bronchoalveolar lavage (BAL) samples from these patients, and these T cells often show evidence of activation and spontaneous secretion of cytokines such as interleukin 2 (IL-2) and interferon gamma (IFNy) - a pattern similar to delayed type hypersensitivity reactions - it is unclear whether both cytokines are produced by the majority of T cells derived from the lungs of patients with sarcoidosis or whether unique subpopulations of T cells produce each cytokine. In this study the properties of T cells cloned from BAL fluid samples of patients with sarcoidosis have been analysed. Methods - T cells were cloned by limiting dilution using IL-2, phytohaemagglutinin, and irradiated feeder cells. Cloning efficiencies were compared and phytohaemagglutinin induced clonal production of IL-2, IFNγ, and IL-4 was determined by bioassay (IL-2 and IFNγ) or ELISA (IL-4). Results - T cells derived from the BAL fluid of patients with sarcoidosis cloned less efficiently than those from blood of the same individuals. Lung derived clones (CD4 + or CD8 + ) produced IFNy more frequently and to a higher titre than blood derived clones, whereas IL-2 production by CD4 + clones derived from BAL fluid was less than that from blood derived clones. Interestingly, IL-4 production by clones from both sites was similar. Analysis of the coproduction of IL-2, IFNγ, and IL-4 by these BAL fluid clones did not demonstrate a predominant "Thl"-like population which has been suggested to underlie delayed type hypersensitivity reactions. Conclusions - The reduced cloning efficiency of T cells from the lung compared with the blood in sarcoidosis is consistent with, although probably more pronounced than, previous observations in normal lungs and shows that T cell hyporesponsiveness is not overcome in the lungs of patients with sarcoidosis. Furthermore, major differences exist between the cytokine producing potential of T cells derived from the lung and the blood in sarcoidosis, and these parallel the differences in the properties of blood and lung T cells seen in healthy individuals.