State of the Art. Role of CD4+ T Cells in Sarcoidosis

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Abstract
Activated pulmonary CD4+ T lymphocytes of the Th-1 type are essential for the inflammatory process in sarcoidosis, and IFN-γ production is crucial for the characteristic granuloma formation. Both the T cells and their inflammatory mediators may constitute possible targets for immunotherapy. A particular T-cell subset, the T-cell receptor (TCR) AV2S3+ bronchoalveolar lavage (BAL) CD4+ T cells, is found at dramatically increased levels in the BAL fluid of human leukocyte antigen (HLA)-DRB1*0301–positive and/or HLA-DRB3*0101–positive patients with sarcoidosis. The AV2S3+ BAL CD4+ T cells strongly associate with the sarcoid inflammation, and future studies on this particular T-cell subset to reveal their specificity may lead to the identification of sarcoidosis-specific antigen(s). T-cell subpopulations with regulatory functions (i.e., natural killer T cells and T regulatory cells) have recently been described as abnormal in sarcoidosis. Dysfunctional regulatory T cells may allow T effector cells to contribut...