CD8 lymphocyte subsets in active polymyalgia rheumatica: comparison with elderly-onset and adult rheumatoid arthritis and influence of prednisone therapy.

The aim of this study was to evaluate CD8 lymphocyte subsets in active polymyalgia rheumatica (PMR), to determine whether low percentages of CD8+ cells could be used to differentiate PMR from elderly-onset (EORA) and adult rheumatoid arthritis (RA), and to investigate the effects of prednisone on CD8 lymphocyte subsets. A significant reduction of percentages and absolute numbers of CD8bright+ cells was observed in patients with active PMR. Both CD8bright+, CD57- and CD8bright+, CD57+ subsets were significantly reduced. Reduced percentages of CD8+ cells were observed in 55% of patients with active PMR/giant cell arteritis (GCA), in 23% with EORA and in 44% with adult RA. Prednisone therapy in PMR patients, after only 1 week, increased the lymphocyte count and the absolute numbers of lymphocyte subsets significantly. However, the percentages of CD8bright+ cells remained persistently low for the 2 yr study period in 80% of the patients with low pre-treatment levels. Our results demonstrate that CD8 cell percentage is a poor epidemiological discriminator for PMR diagnosis. Notwithstanding the rise in absolute numbers of CD8 cell subsets induced by prednisone, the persistently low percentages of CD8+ cells in a group of PMR patients indicate an abnormality connected with the disease.