C3receptors ongranulocytes frompatients withrheumatoid arthritis andFelty's syndrome

SUMMARY Theexpression ofreceptors forthethird component ofcomplement (C3R)on polymorphonuclear cells (PMN)frompatients withrheumatoid arthritis (RA)orFelty's syndrome (FS) andhealthy controls (HG)wasstudied bymeansofaresetting technique using oxerythrocytes coated withrabbit 1gMandmousecomplement. Thepercentage of rosette forming PMN (RF-PMN) wasfound tobeincreased inpatients withFS(59%) and patients withRA (47%) compared toHC (18%), whenmeasured directly after cold isolation ofPMN.Incubation at370Cofcoldisolated cells increased thepercentage of RF-PMNinall three groups, although thevalues weresignificantly higher during thefirst 45minofincubation inbothpatient groups. Whenincubated withserumfrompatients withFSat370C, cold isolated donorPMN formed significantly morerosettes thanafter incubation withdonorserum. Thisincrease wasshowntobeduetothepresence of circulating immunecomplexes inthepatient seraandcould bemimicked byincubating donorPMN withaggregated humanIgG.Asa result ofthese experiments itwas demonstrated that theincreased percentages ofPMN withC3Rinpatients withFSorRA aremostlikely caused byaprevious invivo activation ofPMN byimmunecomplexes. The possible effect ofsuch anincrease inC3Rexpression inrelation toPMN function inthese patients isdiscussed.