Circulating CD8+ T cells in polymyalgia rheumatica and giant cell arteritis: a review

During the last few years, there have been several studies on T cell subsets in polymyalgia rheumatica (PMR) and giant cell arteritis (GCA), with conflicting results. Whereas some authors have found normal values of circulating CD8+ T cells, others have found a decreased number. Furthermore, in some studies, the level of CD8+ cells was found to be related to disease activity, and it has been proposed that a decrease of CD8+ T cells be used as a diagnostic criterion for PMR. The purpose of our study was to determine the value of assessing T cell subsets in PMR and GCA.

T lymphocyte subsets were determined by flow cytometry using a whole blood lysis technique in the following groups: 28 PMR and 6 GCA patients before corticosteroid treatment, 20 PMR and 12 GCA patients in clinical remission with steroid treatment, 55 PMR patients in remission without steroid treatment, 17 rheumatoid arthritis (RA) patients before treatment, and 18 age-matched controls with noninflammatory conditions. Total white cell, lymphocyte, and platelet counts, hemoglobin, C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR) were measured by routine techniques. Comparisons were made by the Student's t-test and the Mann-Whitney test. A MEDLINE database search for studies published between 1983 and 1997 was performed.

Compared with noninflammatory controls, CD8+ T cells were not reduced before steroid treatment in patients with active PMR/GCA in proportion (P =.7) or absolute numbers (P =.1). Patients with active disease had significantly lower hemoglobin levels and higher platelet counts, CRP, and ESR than noninflammatory controls (P <.05). When compared with active RA, CD8+ T cells were not reduced in patients with active PMR in proportion (P =.5) or absolute numbers (P =.2). Between these two groups, RA patients were significantly younger (P =.003) and had lower ESR values (P =.003). We did not find significant differences between patients with active PMR/GCA and those in remission with steroid therapy, except for the lower hemoglobin levels and higher platelet count, CRP, and ESR in the active disease group (P <.05). The same results were found when patients with active disease were compared with PMR in remission and no longer on steroid therapy, the only significant differences were those parameters reflecting the acute phase response (hemoglobin levels, platelet count, CRP and ESR).

This study does not confirm the previous findings that the proportion or number of circulating CD8+ T cells are reduced in patients with active PMR/GCA. The utility of the determination of CD8+ T cells for diagnostic and prognostic purpose should be evaluated in a large multicenter study.