DEFECTIVE MITOGEN-INDUCED CELLULAR CYTOTOXICITY IN UNTREATED PATIENTSWITH ACTIVE RHEUMATOID-ARTHRITIS

Peripheral blood mitogen-induced cellular cytotoxicity (MICC) was stud ied in 13 untreated patients with active rheumatoid arthritis (RA; gro up A) and in 5 RA patients with inactive disease (group B), using phyt ohemagglutinin (PHA) as stimulating agent and K562 cells as target cel ls in the chromium-51 release assay. MICC was found to be significantl y reduced in the patients of group A compared with normal subjects (P< 0.01) and the patients of group B (P<0.05). No differences were noted in MICC between group B patients and normal subjects. A statistically significant negative correlation was found between values of patients' MICC and serum C-reactive protein levels (r = -0.685, P<0.01). Furthe rmore, patients' MICC correlated well with patients' peripheral blood natural killer cell activity (P<0.02), as well as with the absolute nu mber of circulating CD8(+) cells. No correlation was found between MIC C and duration of disease, erythrocyte sedimentation rate, serum alpha (2)-globulins, or the titre of serum rheumatoid factor in the patients studied. We concluded that defective MICC in untreated patients with active RA is probably due to the diminution of the number of CD8(+) ce lls, although a qualitative defect of these cells cannot be excluded.