GPR18 Controls Reconstitution of Mouse Small Intestine Intraepithelial Lymphocytes following Bone Marrow Transplantation

PLOS ONE, Dec 2019

Specific G protein coupled receptors (GPRs) regulate the proper positioning, function, and development of immune lineage subsets. Here, we demonstrate that GPR18 regulates the reconstitution of intraepithelial lymphocytes (IELs) of the small intestine following bone marrow transplantation. Through analysis of transcriptional microarray data, we find that GPR18 is highly expressed in IELs, lymphoid progenitors, and mature follicular B cells. To establish the physiological role of this largely uncharacterized GPR, we generated Gpr18-/- mice. Despite high levels of GPR18 expression in specific hematopoietic progenitors, Gpr18-/- mice have no defects in lymphopoiesis or myelopoiesis. Moreover, antibody responses following immunization with hapten-protein conjugates or infection with West Nile virus are normal in Gpr18-/- mice. Steady-state numbers of IELs are also normal in Gpr18-/- mice. However, competitive bone marrow reconstitution experiments demonstrate that GPR18 is cell-intrinsically required for the optimal restoration of small intestine TCRγδ+ and TCRαβ+ CD8αα+ IELs. In contrast, GPR18 is dispensable for the reconstitution of large intestine IELs. Moreover, Gpr18-/- bone marrow reconstitutes small intestine IELs similarly to controls in athymic recipients. Gpr18-/- chimeras show no changes in susceptibility to intestinal insults such as Citrobacter rodentium infections or graft versus host disease. These data reveal highly specific requirements for GPR18 in the development and reconstitution of thymus-derived intestinal IEL subsets in the steady-state and after bone marrow transplantation.

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GPR18 Controls Reconstitution of Mouse Small Intestine Intraepithelial Lymphocytes following Bone Marrow Transplantation

July GPR18 Controls Reconstitution of Mouse Small Intestine Intraepithelial Lymphocytes following Bone Marrow Transplantation Amy M. Becker 0 1 2 3 Derrick J. Callahan 0 1 2 3 Justin M. Richner 0 1 2 3 Jaebok Choi 0 1 2 3 John F. DiPersio 0 1 2 3 Michael S. Diamond 0 1 2 3 Deepta Bhattacharya 0 1 2 3 0 1 Department of Pathology and Immunology, Washington University School of Medicine , Saint Louis , Missouri, United States of America, 2 Department of Medicine, Washington University School of Medicine , Saint Louis , Missouri, United States of America, 3 Department of Molecular Microbiology, Washington University School of Medicine , Saint Louis , Missouri, United States of America, 4 Division of Oncology, Washington University School of Medicine , Saint Louis, Missouri , United States of America 1 Funding: The Transgenic, Microinjection, and Knockout core facility was supported in part by National Institutes of Health grant P30AR48335. D.B. is a New York Stem Cell Foundation-Robertson Investigator. This research was supported by The New York Stem Cell Foundation, National Institutes of Health grants K01DK078318 (D.B.) , T32CA009547 (A.M.B.), and K01DK099395 (A.M.B.). The funders had no role in study design, data collection 2 Editor: Takuma Kato, Mie University Graduate School of Medicine , JAPAN 3 Current address: Program in Cellular and Molecular Medicine, Boston Children's Hospital , Boston, Massachusetts , United States of America Specific G protein coupled receptors (GPRs) regulate the proper positioning, function, and development of immune lineage subsets. Here, we demonstrate that GPR18 regulates the reconstitution of intraepithelial lymphocytes (IELs) of the small intestine following bone marrow transplantation. Through analysis of transcriptional microarray data, we find that GPR18 is highly expressed in IELs, lymphoid progenitors, and mature follicular B cells. To establish the physiological role of this largely uncharacterized GPR, we generated Gpr18-/mice. Despite high levels of GPR18 expression in specific hematopoietic progenitors, Gpr18-/- mice have no defects in lymphopoiesis or myelopoiesis. Moreover, antibody responses following immunization with hapten-protein conjugates or infection with West Nile virus are normal in Gpr18-/- mice. Steady-state numbers of IELs are also normal in Gpr18-/- mice. However, competitive bone marrow reconstitution experiments demonstrate that GPR18 is cell-intrinsically required for the optimal restoration of small intestine TCRγδ+ and TCRαβ+ CD8αα+ IELs. In contrast, GPR18 is dispensable for the reconstitution of large intestine IELs. Moreover, Gpr18-/- bone marrow reconstitutes small intestine IELs similarly to controls in athymic recipients. Gpr18-/- chimeras show no changes in susceptibility to intestinal insults such as Citrobacter rodentium infections or graft versus host disease. These data reveal highly specific requirements for GPR18 in the development and reconstitution of thymus-derived intestinal IEL subsets in the steady-state and after bone marrow transplantation. - Competing Interests: The authors have declared that no competing interests exist. The development and function of immune lineages are regulated by cell-extrinsic cues provided by contact with other cells and microbes, the extracellular matrix, and soluble factors. Intestinal IELs, for example, are localized amongst enterocytes and in close proximity to luminal flora such that they can rapidly respond to barrier injury or infection [1]. Intestinal IELs contain several T cell subsets, including conventional CD4+ and CD8αβ+ TCRαβ+ cells and unconventional lymphocytes expressing CD8αα+ homodimers [2]. These CD8αα+ cells can be further segregated into TCRαβ+ and TCRγδ+ subsets [2–4]. Each of these subsets likely plays unique functional roles. For example, TCRγδ+ IELs limit Salmonella typhimurium dissemination following infection and produce keratinocyte growth factor to mediate epithelial regeneration after injury [5–10]. CD8αβ+ IELs are particularly important for establishing immunity to certain intestinal pathogens, such as Toxoplasma gondii, while CD4+ IELs in the large intestine are essential for protection against enteric pathogens such as Citrobacter rodentium [11, 12]. Although the functional importance of IELs is increasingly becoming clear, the guidance cues which direct these specialized T cells to colonize the intestinal epithelium are not fully understood. To ensure access to the appropriate extrinsic signals, IELs must be positioned properly through the combined action of adhesion molecules and chemokine signals [13]. Initial entry into Peyer's patches, the lamina propria, and intraepithelial regions depends upon the expression of integrin β7 [14–16], although the specific α chain pairing depends upon the lymphocyte subset and ultimate destination. Integrin α4β7 mediates binding to the Peyer's Patch high endothelial venules and is essential for entry into the mucosa by con (...truncated)


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Amy M. Becker, Derrick J. Callahan, Justin M. Richner, Jaebok Choi, John F. DiPersio, Michael S. Diamond, Deepta Bhattacharya. GPR18 Controls Reconstitution of Mouse Small Intestine Intraepithelial Lymphocytes following Bone Marrow Transplantation, PLOS ONE, 2015, Volume 10, Issue 7, DOI: 10.1371/journal.pone.0133854