title: Differential expression of chemokine receptors on peripheral blood, synovial fluid, and synovial tissue monocytes/macrophages in rheumatoid arthritis.
abstract: OBJECTIVE
  Since it is likely that monocytes utilize chemokines to migrate to the rheumatoid arthritis (RA) joint, we investigated the expression of C-C chemokine receptors (CCR) 1-6 and C-X-C receptor 3 (CXCR3) in the peripheral blood (PB), synovial fluid (SF), and synovial tissue of patients with RA as well as in the PB of normal subjects.
  
  
  METHODS
  We compared chemokine receptor expression on CD14+ monocytes from normal PB, RA PB, and RA SF using 2-color flow cytometry. Correlations with patient clinical data were determined. Chemokine and receptor expression were investigated in RA synovial tissue by immunohistochemistry and 2-color immunofluorescence to identify CD68+ macrophages.
  
  
  RESULTS
  Most normal PB monocytes expressed CCR1 (87%) and CCR2 (84%), but not CCRs 3, 4, 5, or 6 or CXCR3. RA PB monocytes expressed CCR1 (56%) and CCR2 (76%), with significantly more expressing CCR3 (18%), CCR4 (38%), and CCR5 (17%) compared with normal PB monocytes. Significantly fewer SF monocytes from RA patients expressed CCR1 (17%), CCR2 (24%), and CCR4 (6%) while significantly more expressed CCR3 (35%) and CCR5 (47%) compared with RA and normal PB monocytes; CCR6 and CXCR3 were rarely detected. Clinically, the erythrocyte sedimentation rate was inversely correlated with the expression of CCR1 and CCR4 by RA PB, and CCR5 expression by RA SF was correlated with the SF white blood cell count. CCR1-, CCR2-, and CCR5-immunoreactive cells were found in RA synovial tissue and colocalized with CD68+ macrophages. RA synovial tissue RANTES (regulated upon activation, normally T cell expressed and secreted chemokine)- and monocyte chemoattractant protein 1-immunoreactive cells colocalized with CCR1 and CCR2, respectively, on serial sections. Macrophage inflammatory protein 1alpha (MIP-1alpha) was principally restricted to vascular endothelium, and MIP-1beta+ macrophages were found throughout the sections.
  
  
  CONCLUSIONS
  Monocytes mainly express CCR1 and CCR2 in normal and RA PB, CCR3 and CCR5 in RA PB and RA SF, and CCR4 in RA PB. The differential expression of chemokine receptors suggests that certain receptors aid in monocyte recruitment from the circulation while others are important in monocyte retention in the joint.
authors.affiliation: Northwestern University Medical School, Chicago, Illinois 60611, USA.
authors.forename: K J
authors.initials: KJ
authors.lastname: Katschke
authors.forename: J B
authors.initials: JB
authors.lastname: Rottman
authors.forename: J H
authors.initials: JH
authors.lastname: Ruth
authors.forename: S
authors.initials: S
authors.lastname: Qin
authors.forename: L
authors.initials: L
authors.lastname: Wu
authors.forename: G
authors.initials: G
authors.lastname: LaRosa
authors.forename: P
authors.initials: P
authors.lastname: Ponath
authors.forename: C C
authors.initials: CC
authors.lastname: Park
authors.forename: R M
authors.initials: RM
authors.lastname: Pope
authors.forename: A E
authors.initials: AE
authors.lastname: Koch
mesh_terms: D000328:Adult; D001172:Arthritis, Rheumatoid / Q000276:immunology* / Q000378:metabolism*; D018932:Chemokine CCL2 / Q000276:immunology / Q000378:metabolism; D018946:Chemokine CCL5 / Q000276:immunology / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D008297:Male; D009000:Monocytes / Q000276:immunology / Q000378:metabolism; D054399:Receptors, CCR6; D054367:Receptors, CXCR3; D019718:Receptors, CXCR4 / Q000096:biosynthesis / Q000276:immunology; D054380:Receptors, CXCR5; D019707:Receptors, Chemokine / Q000096:biosynthesis* / Q000276:immunology; D018121:Receptors, Cytokine / Q000096:biosynthesis / Q000276:immunology; D023062:Receptors, Interleukin-8A / Q000096:biosynthesis / Q000276:immunology; D023063:Receptors, Interleukin-8B / Q000096:biosynthesis / Q000276:immunology; D013582:Synovial Fluid / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D013583:Synovial Membrane / Q000166:cytology / Q000276:immunology / Q000378:metabolism*
chemical_list: C106311:CCR6 protein, human; C515187:CXCR3 protein, human; C095085:CXCR5 protein, human; D018932:Chemokine CCL2; D018946:Chemokine CCL5; D054399:Receptors, CCR6; D054367:Receptors, CXCR3; D019718:Receptors, CXCR4; D054380:Receptors, CXCR5; D019707:Receptors, Chemokine; D018121:Receptors, Cytokine; D023062:Receptors, Interleukin-8A; D023063:Receptors, Interleukin-8B