Basic Study
Copyright ©The Author(s) 2017. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. May 14, 2017; 23(18): 3240-3251
Published online May 14, 2017. doi: 10.3748/wjg.v23.i18.3240
Thiopurine use associated with reduced B and natural killer cells in inflammatory bowel disease
James D Lord, Donna M Shows
James D Lord, Donna M Shows, Translational Research Program, Benaroya Research Institute, Seattle, WA 98101, United States
James D Lord, Gastroenterology Division, Virginia Mason Medical Center, Seattle, WA 98101, United States
Author contributions: Lord JD designed experiments, analyzed data, and wrote the paper; Shows DM performed cell purification, culture and flow cytometry experiments.
Supported by Virginia Mason Medical Center, Digestive Disease Institute Research Grant Award, No. 0506812-2011.
Institutional review board statement: The study was reviewed and approved by the Virginia Mason Medical Center/Benaroya Research Institute Institutional Review Board.
Conflict-of-interest statement: All authors report no potential conflicts of interest with the data in this manuscript.
Data sharing statement: FCS files of flow cytometry data used to generate this manuscript are available upon request from the corresponding author (below).
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: James D Lord, MD, PhD, Research Assistant Member, Translational Research Program, Benaroya Research Institute, 1201 Ninth Avenue, Seattle, WA 98101, United States. jlord@benaroyaresearch.org
Telephone: +1-206-2871088 Fax: +1-206-2875682
Received: December 15, 2016
Peer-review started: December 17, 2016
First decision: December 29, 2016
Revised: January 27, 2017
Accepted: March 15, 2017
Article in press: March 15, 2017
Published online: May 14, 2017
Processing time: 150 Days and 22.5 Hours
Abstract
AIM

To identify which blood and mucosal lymphocyte populations are specifically depleted by thiopurine use in vivo.

METHODS

The thiopurines azathioprine and 6-mercaptopurine have been a mainstay of inflammatory bowel disease (IBD) therapy for decades, but their mechanism of action in vivo remains obscure. Although thiopurines are lymphotoxic at high doses, and have been reported to cause T cell apoptosis in vitro, their ability to control IBD at lower doses suggests that they may selectively deplete particular lymphocyte populations. Blood cells from 19 IBD patients on a thiopurine, 19 IBD patients not on a thiopurine, and 38 matched healthy control subjects were analyzed by multiple multi-color flow cytometry panels to quantify the immune cell subsets contained therein, both as a percent of cells, and as an absolute cell count. Similar analyses were performed on colon biopsies from 17 IBD patients on a thiopurine, 17 IBD patients not on a thiopurine, and 49 healthy screening colonoscopy recipients.

RESULTS

Complete blood counts revealed lower lymphocyte, but not monocyte or granulocyte, counts in IBD patients who were taking thiopurines at the time of sampling. This reduction was restricted to CD3-negative lymphocytes, wherein both natural killer (NK) and B cells were significantly reduced among thiopurine recipients. Among CD19+ B cells, the transitional B cells were particularly depleted, being nearly absent in both blood and colon biopsies of thiopurine recipients. No differences were associated with thiopurine use in CD8+ T cells, mucosa-associated invariant T (MAIT) cells, invariant natural killer T (iNKT) cells, gamma/delta T cells, Th1, Th17, regulatory T cells (Tregs) or naïve CD4+ T cells. However, patients with IBD had significantly more circulating FOXP3+, Helios+ Tregs and fewer iNKT and MAIT cells than healthy controls.

CONCLUSION

Thiopurine use is associated with reduced B and NK cell, but not T cell, subpopulations in the blood of IBD patients.

Keywords: Thiopurine; Azathioprine; Mercaptopurine; Lymphocyte; Natural killer cell; Transitional B cell; Inflammatory bowel disease

Core tip: Thiopurine medications have been used to treat inflammatory bowel disease (IBD) for almost half a century. However, the effect of thiopurines on the human immune system in vitro remains unclear. The enclosed manuscript performed a thorough flow cytometric analysis of peripheral blood specimens from IBD patients with or without thiopurine therapy and found significant differences in B and NK cell populations associated with therapy. These suggest that thiopurines function to suppress inflammation in IBD not by causing T cell apoptosis, as had been suggested by in vitro data, but rather by depleting other lymphocytes.