QUANTITATION OF IL-2RP75 (CD122) EXPRESSION ON MONONUCLEAR-CELLS IN RHEUMATIC DISEASE

Objective-To compare expression of the p75 chain of the interleukin-2 receptor (IL-2Rp75, CD122) on peripheral and synovial mononuclear cell s in rheumatoid and non-rheumatoid inflammatory arthritis. Methods-Per ipheral blood (PBMC) and synovial (SFMC) mononuclear cells were isolat ed from subjects with rheumatoid arthritis (n = 16) and non-rheumatoid inflammatory arthritis (n = 12). PBMC were isolated from six healthy controls. Expression of CD122 was examined using indirect immunofluore scence and quantitative flow cytometry. Results-There was no differenc e in IL-2Rp75 expression on PBMC from rheumatoid arthritis patients, n onrheumatoid arthritis patients, and controls. In subjects with rheuma toid arthritis group there was an increase in IL-2Rp75 expression on S FMC compared with PBMC (P = 0.0032). On SFMC there was a greater expre ssion of IL-2Rp75 in non-rheumatoid arthritis than in rheumatoid arthr itis (P = 0.0007). Expression was greater on CD8 positive cells and in subjects with shorter duration of disease. Conclusions-The p75 chain of the IL-2 receptor, an important T cell activation antigen, is not u pregulated in synovial fluid. This appears to be a disease specific de fect and provides further support for the concept of ''frustrated'' or incomplete T cell activation in this disease.