BLOOD MONOCYTES IN RHEUMATOID-ARTHRITIS ARE HIGHLY ADHERENT TO CULTURED ENDOTHELIUM

Monocytes from 17 patients with rheumatoid arthritis (RA) were more ad herent than monocytes from 17 control patients to monolayers of pig ao rtic endothelium irrespective of whether sera was included (median 27- 34% increase; p = 0.002) or omitted (median 27% increase; p = 0.022) f rom the culture media. When human umbilical vein endothelial cells wer e used as the adherence substrate, rheumatoid monocytes from an additi onal 21 patients demonstrated a median 31% (p = 0.004) and 20% increas e (p = 0.004) in adhesion when compared with monocytes from 21 normal healthy subjects in the absence and presence of autologous sera, respe ctively. Activation of control monocytes with muramyl dipeptide or tre atment with RA sera increased their attachment to endothelium (mean 34 +/-14% increase; p<0.001). The expression of the adhesion molecules CD 11b (p<0.005), CD18 (p<0.005), CD62L (p = 0.01) was enhanced on rheuma toid monocytes, but antibody-blocking studies suggested that CD18 and CD62L were not responsible for the augmented binding of the rheumatoid cells. A subpopulation of rheumatoid monocytes possessed a very low n et negative surface charge, a property that favours binding to vessel walls. We propose that many rheumatoid monocytes are predisposed for s heer-resistant adhesion to vascular endothelium.