Soluble interleukin-2 receptor and soluble CD8 antigen in active rheumatoid arthritis

Abstract

Concentrations of soluble interleukin-2 receptor (sIL-2R) and of soluble CD8 antigen (sCD8) in sera and in supernatants of phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells (PBMC) derived from patients with active rheumatoid arthritis (RA) were studied. sIL-2R concentrations in sera derived from patients with RA (1484 ± 382 U/ml) were significantly higher than in sera derived from healthy controls (380 ± 110 U/ml; P < 0.0005). In contrast, supernatants of PHA-stimulated PBMC derived from patients with RA contained similar amounts of sIL-2R (727 ± 467 U/ml) as those derived from healthy control individuals (833 ± 508 U/ml; P > 0.1). When investigated for the presence of sCD8 antigen, sera derived from patients with RA contained significantly lower amounts (30 ± 28 U/ml) than sera derived from healthy controls (405 ± 136 U/ml; P < 0.0005). Similarly, PHA stimulation of PBMC derived from patients with RA resulted in a significantly lower production of sCD8 (35 ± 46 U/ml) as compared to the one obtained by PHA stimulation of PBMC derived from healthy controls (177 ± 59 U/ml; P < 0.0005). This difference could not be explained by a lower proliferative response to PHA by PBMC derived from patients with RA (21,474 ± 14,022 cpm) as compared to healthy controls (29,549 ± 11,188 cpm; P > 0.05). Our data demonstrate that PBMC derived from patients with active RA differ from PBMC derived from healthy individuals concerning their ability to produce sIL-2R and sCD8.