T lymphocytes in giant cell arteritic lesions are polyclonal cells expressing alpha beta type antigen receptors and VLA-1 integrin receptors.

Giant cell arteritis (GCA) is a common disease in the elderly. It is characterized by focal inflammatory lesions dominated by T lymphocytes and macrophages. The etiology of GCA is, however, still unknown. The aim of the present study was to determine whether lesional T cells represent clonal proliferations, and to characterize adhesion receptors that could be important for recruitment of T cells and antigen receptors involved in their activation. Temporal artery biopsies were obtained from 13 patients presenting with clinical signs of GCA. Immunohistochemistry was used to characterize cell surface receptors on CD3+ T cells in situ in the lesions of eight patients with biopsy-verified GCA. The overwhelming majority of T cells in GCA lesions expressed the TCR alpha beta receptors. In sections from three of eight patients, a small proportion of cells expressing TCR gamma delta was also seen. Almost all T cells expressed the integrin receptors, LFA-1 and VLA-1, as determined by double-staining. To characterize the clonal composition of the lesional T cell population, cells were isolated by collagenase digestion of two lesions and T cells cloned by limiting dilution in the presence of mitogenic antibodies, IL-2 and autologous feeder cells. Rearrangements of the T cell receptor (TCR) genes of the clones were analysed by Southern hybridization using probes for TCR gamma and beta genes. T cell clones established from GCA lesions exhibited heterogeneous rearrangement patterns, indicating a polyclonal origin of the cells. We conclude that GCA lesions contain T lymphocytes that are of polyclonal origin and express integrin-type adhesion receptors. This supports the hypothesis that GCA involves an inflammatory response during which polyclonal T cells adhere to arterial tissue components and accumulate in the developing lesions.