Elsevier

Clinical Immunology

Volume 141, Issue 2, November 2011, Pages 169-176
Clinical Immunology

Therapeutic in vivo selection of thymic-derived natural T regulatory cells following non-myeloablative hematopoietic stem cell transplant for IPEX

https://doi.org/10.1016/j.clim.2011.07.005Get rights and content

Abstract

FOXP3 is critical for the development and function of CD4+CD25bright natural regulatory T cells (nTreg). Individuals harboring mutations in FOXP3 develop immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome (IPEX). We describe a child diagnosed with IPEX who underwent a reduced intensity, T and B cell depleted, matched unrelated donor bone marrow transplant followed by clinical resolution. Using lineage-specific donor chimerism studies, we demonstrate that non-myeloablative HSCT resolves disease in the context of low level donor hematopoietic stem cell (HSC) engraftment. Despite low-levels of donor HSC, thymically-derived nTreg and to a lesser extent CD4+ and CD8+ T cells, exhibit a selective in vivo growth advantage for populations containing a functional FOXP3 gene. Moreover, nTreg from this patient show regulatory function directly ex vivo. These results have implications for improving clinical therapy for patients with IPEX and provide mechanistic insight into the in vivo development of human nTreg and unexpectedly, non-regulatory T cells.

Introduction

Natural regulatory T cells (nTreg) are characterized by a general CD4+CD25brightCD127loFOXP3+ phenotype, with additional molecules potentially serving to delineate functional subgroups [3], [4], [5], [9], [10], [13], [15], [21]. FOXP3 is a winged/helix forkhead transcription factor crucial for nTreg development and function. While FOXP3 has been a useful lineage specification marker in rodents, analogous immune monitoring studies in humans have been complicated by species-specific differences in gene regulation [20]. Two notable differences are that all human T cells transiently express FOXP3 without commensurate acquisition of suppressive function [1], [17], [19], [25]. This trait raises the possibility of an additional role for FOXP3 in general T cell function, as well as for those with regulatory activity. Another distinct feature of human FOXP3 is the expression of two protein isoforms; a full length molecule and shorter protein lacking the amino acids encoded by exon 2 [27]. The unique biology of FOXP3 highlights the need for additional studies which provide insight into the in vivo development and function of human nTreg.

Most patients with IPEX do not live beyond 3 years of age. Immunosuppressive therapy has been generally ineffective and hematopoietic stem cell transplantation (HSCT) remains the only curative option. Conventional myeloablative conditioning prior to HSCT has resulted in substantial regimen-related mortality, whereas reduced intensity conditioning has been used with some success [8], [14], [18], [26]. Here, we used lineage-specific donor chimerism studies to demonstrate that non-myeloablative HSCT can resolve clinical symptoms of IPEX in the context of low level donor hematopoietic stem cell (HSC) engraftment. We demonstrate a selective in vivo growth advantage of nTreg, as well as CD4+ and CD8+ T cells, from a minority population of donor HSC having a functional FOXP3 gene. These results have implications for improving clinical therapy for patients with IPEX and provide evidence for a previously unappreciated role for FOXP3 in the development of CD4+ and CD8+ T cells.

Section snippets

Patient

A six week old white male presented with a generalized, pruritic, desquamating rash, feeding intolerance, diarrhea and failure to thrive. He developed multiple infections including pneumocystis pneumonia and bacteremia with enteric pathogens. Maternal family history revealed multiple male infant deaths. Pertinent laboratory findings included a peripheral blood eosinophilia of 27%, a hemoglobin level of 9.1 g/L, positive direct antiglobulin test (DAT), albumin level of 1.9 gm/dL, IgE initially

Results and discussion

We describe a 6 week male infant diagnosed with IPEX who harbored an A384T mutation in FOXP3 and examine the molecular dynamics of hematopoietic development and homeostasis following non-myeloablative HSCT (see Methods for case description). Prior to HSCT, the patient had a slightly higher percentage of CD4+CD25bright T cells compared to his mother (20% vs. 14%). Notably, a markedly reduced proportion of patient T cells (gated on the CD4 + CD25bright subset as shown in Fig. 2B) stained for FOXP3

Conflicts of interest

The author(s) declare that there are no conflicts of interest.

Acknowledgments

The authors would like to thank Dr. Mary Ellen Conley and members of the Department of Bone Marrow Transplantation and Cellular Therapy for care of the patient, Jim Houston and Drs. Ann Marie Hamilton-Easton and Richard Ashmun for invaluable assistance with flow cytometry, and members of the Molecular Pathology Lab at SJCRH for assistance with VNTR analysis. This work was supported by the Assisi Foundation of Memphis, Cancer Center Support Grant 2P30CA021765 and the American Lebanese and Syrian

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    1

    These authors contributed equally to the work.

    2

    Current address: Bone Marrow and Stem Cell Transplantation Program, University of North Carolina, Chapel Hill, NC, 27599, USA.

    3

    Current address: Department of Bone Marrow Transplantation and Cellular Therapy, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA.

    4

    Current address: Department of Hematology, St. Jude Children's Research Hospital, Memphis, TN, 38105, USA.

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