Role of peripheral CD8 lymphocytes and soluble IL-2 receptor in predicting the duration of corticosteroid treatment in polymyalgia rheumatica and giant cell arteritis.

Objectives: To determine if the presence of low percentages of CD8 positive cells or high levels of soluble interleukin-2 receptors (sIL-2R) define a subgroup of patients with more severe polymyalgia rheumatica and giant cell arteritis (PMR/GCA).

Methods: 38 PMR/GCA patients were followed up prospectively. Serum levels of sIL-2R and peripheral blood CD8 lymphocytes were measured before the start of corticosteroid treatment, after six months of treatment and at the last visit. Phenotypical analysis of lymphocyte subpopulations was performed with a two colour technique, and assay of sIL-2R was performed using an enzyme-linked immunosorbent kit. Forty four healthy people matched for age and gender comprised a healthy control group.

Results: The median duration of follow up was 28 months (range 7-65). Corticosteroid treatment lasted a median of 23.5 months (7-65). Eleven patients (29%) were in remission at the end of follow up; 45% of the patients had at least one relapse or recurrence. Compared with controls, patients with active disease had a significantly lower percentage of CD8 cells and significantly increased sIL-2R levels. Erythrocyte sedimentation rate, C reactive protein, and sIL-2R values were significantly less after six months of steroid treatment compared with before treatment. The percentage of CD8 cells remained significantly lower at six months and the end of follow up compared with controls, while sIL-2R levels remained significantly greater. Patients in whom the percentage of CD8 cells at six months was lower than one SD of the mean of normal controls (26%) had a significantly longer duration of corticosteroid treatment, a greater cumulative dose of prednisone and more relapses or recurrences compared with patients in whom the percentage was in the normal range. The duration of treatment and the cumulative dose of prednisone were not influenced by the percentage of CD8 cells before treatment therapy or by the levels of sIL-2R after six months of treatment.

Conclusions: A reduced percentage of CD8 cells after six months of treatment may be a useful outcome parameter which would identify a group of PMR/GCA patients likely to experience more severe disease, defined as longer duration of corticosteroid treatment, higher cumulative dose of prednisone, and relapse or recurrence of disease.