Increased numbers of immature plasma cells in peripheral blood specifically overexpress chemokine receptor CXCR3 and CXCR4 in patients with ulcerative colitis.

Ulcerative colitis (UC) is a chronic inflammatory bowel disease featuring infiltration by plasma cells producing immunoglobulins. We have reported previously the specific and significant proliferation of immature plasma cells in the inflamed colonic and pouch mucosa of UC patients. The aim of this study was to characterize peripheral blood immature plasma cells and the migration mechanisms of such immature plasma cells to inflamed sites in UC. The characteristics of peripheral blood immature plasma cells and chemokine receptor expression were examined by flow cytometry. Expression of mucosal chemokine was quantified using real-time reverse transcription-polymerase chain reaction and immunohistochemistry. The number of peripheral blood immature plasma cells was significantly higher in patients with active UC and active Crohn's disease (CD) than in healthy controls. The proportion of immature plasma cells was correlated positively with clinical activities of UC and CD. Many peripheral blood immature plasma cells were positive for CXCR3, CXCR4, CCR9 and CCR10. Expression of CXCR3 and CXCR4 in UC patients was significantly higher than in controls. CXCL9, CXCL10 and CXCL11 mRNA levels in colonic mucosa of inflamed IBD were higher than in controls. Immunofluorescence study also showed abundant CXCR3-positive immature plasma cells in the inflamed colonic mucosa of UC. Increased numbers of immature plasma cells may migrate towards inflammatory sites of UC via the CXCR3 axis, and may participate in UC pathogenesis.