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Background: Thiopurines are considered immunosuppressive agents and may be associated with an increased risk for infections. However, few inflammatory bowel disease (IBD) patients are appropriately vaccinated, and data on their ability to mount an immune response are vague. We evaluated the effects of the thiopurines, azathioprine (AZA) and 6-mercaptopurine (6-MP), on cellular and humoral immune responses in IBD patients., Methods: A prospective clinical investigation was conducted on IBD patients referred for thiopurine treatment. Immune competence was evaluated by assessing lymphocyte counts and phenotype, response to mitogen and antigen stimulation, immunoglobulin levels, and response to pneumococcal and tetanus vaccines (before treatment, week 0), and to Haemophilus influenza type b vaccine (at week 24)., Results: Thirty-one Crohn's disease and 12 ulcerative colitis patients who completed at least 24 weeks of therapy were included. The posttherapy average 6-MP dose was 1.05 ± 0.30 mg/kg, and white blood cell counts had decreased significantly from baseline values (P < 0.002). The posttreatment response to mitogens and antigens and the immunoglobulin levels were unchanged. Responses to vaccines were normal both in thiopurine-naïve and thiopurine-treated patients, suggesting that these patients were immunologically intact while on thiopurine therapy and capable of generating normal immune responses in vivo., Conclusions: There is no evidence for any intrinsic systemic immunodeficiency in IBD patients. Thiopurines at the doses used for treating IBD showed no significant suppressive effect on the systemic cellular and humoral immune responses evaluated. Thiopurine-treated IBD patients can be safely and efficiently vaccinated., (Copyright © 2011 Crohn's & Colitis Foundation of America, Inc.)

IBDs are characterized by increased influx of immune cells to the mucosa of genetically susceptible persons. Cellular migration to injury sites is mediated by chemokines. CXCL12 is a ubiquitous, constitutive chemokine that participates in stem cell proliferation and migration and mediates T lymphocyte migration to inflamed tissues. We have recently reported that CXCL12 and its receptor, CXCR4, are expressed in normal and more prominently, inflamed human intestinal mucosa. However, the interactions and roles of CXCL12 and its receptors, CXCR4 and the recently discovered CXCR7, in intestinal inflammation have not been defined. In the present study, we further dissected the effects of CXCL12 on lymphocytes in intestinal homeostasis and inflammation and delineated the interplay between CXCL12 and its receptors CXCR4 and CXCR7. To that end, fresh mononuclear cells were isolated from mucosa and PB of healthy or IBD patients. Phenotypical and functional assays were conducted using flow cytometry, Transwell migration chambers, and ELISA. The data show that CXCL12-mediated migration of T cells is CXCR4- but not CXCR7-dependent. T cell activation reciprocally regulates CXCR7 and CXCR4 expression and migratory capacity. IBD PBTs expressed more CXCR7 than normal PBTs. Finally, T cells attracted by CXCL12 are mostly of a memory phenotype. In conclusion, the present study suggests that the interplay between CXCL12 and its receptors affects homeostasis and inflammation in the intestinal mucosa.

Background: Inflammatory bowel disease (IBD) is characterized by increased lymphocytic infiltrate to the lamina propria (LP) and upregulation of inflammatory chemokines and receptors. CXCL12 is a constitutive chemokine involved in lung, brain, and joint inflammation. We hypothesized that CXCL12 and its receptor, CXCR4, would have a constitutive and inflammatory role in the gut., Methods: Intestinal epithelial cells (IECs) and T lymphocytes were isolated from intestinal mucosa of IBD and control patients undergoing bowel resection. Autologous T cells were isolated from peripheral blood (PB). CXCL12 and CXCR4 expression by IECs was assessed by polymerase chain reaction and immunohistochemistry, lymphocyte phenotype by flow cytometry, and migration by Transwells., Results: IECs expressed CXCL12 and expression was increased and more diffuse in IBD compared to normal crypts (ulcerative colitis [UC] > Crohn's disease [CD], inflamed > noninflamed). CXCR4 was expressed by IECs, LP T cells (LPTs), and PB T cells (PBTs), and CXCR4+ cells were increased in IBD LP in situ. PBTs and LPTs from all patients had a high and comparable migration toward CXCL12 (P < 0.0001 and P < 0.05 vs. medium, respectively). Migration toward IBD-IEC-derived supernatant was significantly higher compared to normal. Antibodies against CXCR4 and CXCL12 blocked migration., Conclusions: CXCL12 is expressed by normal IECs and upregulated and differentially distributed in IBD IECs. CXCR4 is expressed by IECs and LPTs, and CXCR4+ cells are significantly increased in IBD LP. CXCL12 is chemotactic for both PBTs and LPTs. Thus, CXCL12 and CXCR4 have a constitutive and inflammatory role in the intestinal mucosa and their selective therapeutic manipulation may be considered in IBD management.