INTERLEUKIN-1, INTERLEUKIN-1 RECEPTOR ANTAGONIST AND MACROPHAGE POPULATIONS IN RHEUMATOID-ARTHRITIS SYNOVIAL-MEMBRANE

To determine whether interleukin-1 (IL-1) and interleukin-1 receptor a ntagonist (IL-1ra) are produced by different macrophage subsets, we ap plied immunoperoxidase and double-labelling immunofluorescence techniq ues to 10 rheumatoid arthritis (RA) and 10 osteoarthritis (OA) synovia l membranes. In RA, greater numbers of early 27E10+ macrophages were f ound in the sublining layer while mature 25F9+ macrophages were more a bundant in the lining layers. The majority of IL-1 alpha+ cells were a lso IL-1ra+ (79 +/- 12% sublining layer, 98 +/- 2% lining layer). In O A sublining layer, a higher percentage of cells double stained for 25F 9 and IL-1ra was detected compared to those double stained for 25F9 an d IL-1 alpha (P < 0.004). In OA, 25F9+ macrophages demonstrated a lowe r percentage of IL-1 alpha+ in the lining and sublining layers compare d to RA (P < 0.02 and P < 0.004, respectively). It may be concluded th at once monocytes have migrated into the RA joint, they undergo phenot ypic and functional changes from an early profile (27E10+, CD14+, low percentage of IL-1+ and IL-1ra+ cells) to a mature profile (CD14+/-, 2 5F9+, RM3/1+, high percentage of IL-1+ and IL-1ra+ cells).