Reduced T-cell repertoire restrictions in abatacept-treated rheumatoid arthritis patients.

BACKGROUND: CD28(neg) T cells, which display functional characteristic of oligoclonally expanded cytotoxic memory T lymphocytes, are believed to be pathologically relevant in rheumatoid arthritis manifestation. The CD28 co-stimulation blockade by abatacept can prevent the generation of CD28(neg) T-cell populations in these patients. METHODS: Samples were obtained before and after 12 months of abatacept therapy. T-cell phenotype and T-cell receptor diversity were evaluated by flow cytometry and complementarity-determining region-3 spectratyping, respectively, while telomerase reverse-transcriptase gene level was measured by real-time PCR. RESULTS: Abatacept induces a decrease of the percentage and number of CD4(+)CD28(neg) T cells and a reduction of T-cell repertoire restrictions; these features are directly correlated. Thymic output and telomerase activity are not modified by the therapy. CONCLUSIONS: Abatacept-induced decrease of peripheral T-cell repertoire restrictions can due to a reduced generation of senescent, chronically stimulated CD4(+)CD28(neg) T cells.