Cytotoxic T cell clones from the lungs of systemic sclerosis patients with alveolitis

Activated CD8⁺ T cells are increased in bronchoalveolar lavage (BAL) fluids from systemic sclerosis (SSc) patients with alveolitis. Analysis of T cell antigen receptor (TCR) expression by BAL CD8⁺ T cells shows a consistent pattern of junctional region lengths in some TCR V gene families over time. Predominance of one or two TCR junctional lengths suggests an oligoclonal expansion of these T cells. We hypothesize that oligoclonal CD8⁺ T cells cause tissue damage in SSc through cytolytic and cytokine effects. To test this, we isolated and cloned Vβ3⁺CD8⁺ T cells from BAL fluid from patient 1, Vβ12⁺CD8⁺ T cells from patient 2, Vβ16⁺CD8⁺ T cells from patient 3, Vβ17⁺CD8⁺ T cells from patient 4, and Vβ20⁺CD8⁺ T cells from patient 5. Expression of CD8 and the desired TCRVβ on the T cell clones was confirmed by flow cytometry and DNA sequence analysis. Of 72 clones, 37 have been tested to date for functional activities. These T cell clones had cytolytic activity against autologous fibroblasts and Epstein-Barr virus-transformed B cells. The T cells used the perforin-mediated pathway for target cell lysis, which could be blocked by concanamycin A. CD28⁺CD8⁺ clones had higher cytolytic activity than CD28^-CD8⁺ ones. Analysis of cytokine mRNAs expression showed that the majority (20/37) of CD8⁺ T cell clones from SSc patients had Tc2 phenotype, producing IL-4 and IL-10, but not IFNγ or IL-2. In contrast, only 3/12 CD8⁺ T cell clones from a control BAL fluid had Tc2 pattern of cytokine production. These data suggest that clonally expanded CD8⁺ T cells in the lungs of SSc patients may contribute to tissue damage through cytolytic activity and cytokine production.