Abstract
Regulatory T cells (Tregs) were identified several years ago and are key in controlling autoimmune diseases and limiting immune responses to foreign antigens, including alloantigens. In vivo imaging techniques including intravital microscopy as well as whole body imaging using bioluminescence probes have contributed to the understanding of in vivo Treg function, their mechanisms of action and target cells. Imaging of the human sodium/iodide symporter via Single Photon Emission Computed Tomography (SPECT) has been used to image various cell types in vivo. It has several advantages over the aforementioned imaging techniques including high sensitivity, it allows non-invasive whole body studies of viable cell migration and localisation of cells over time and lastly it may offer the possibility to be translated to the clinic. This study addresses whether SPECT/CT imaging can be used to visualise the migratory pattern of Tregs in vivo. Treg lines derived from CD4+CD25+FoxP3+ cells were retrovirally transduced with a construct encoding for the human Sodium Iodide Symporter (NIS) and the fluorescent protein mCherry and stimulated with autologous DCs. NIS expressing self-specific Tregs were specifically radiolabelled in vitro with Technetium-99m pertechnetate (99mTcO4 −) and exposure of these cells to radioactivity did not affect cell viability, phenotype or function. In addition adoptively transferred Treg-NIS cells were imaged in vivo in C57BL/6 (BL/6) mice by SPECT/CT using 99mTcO4 −. After 24 hours NIS expressing Tregs were observed in the spleen and their localisation was further confirmed by organ biodistribution studies and flow cytometry analysis. The data presented here suggests that SPECT/CT imaging can be utilised in preclinical imaging studies of adoptively transferred Tregs without affecting Treg function and viability thereby allowing longitudinal studies within disease models.
Highlights
Regulatory T cells (Tregs) are key players in the adaptive immune system
We have shown that Tregs can be retrovirally transduced with myeloproliferative sarcoma virus to express an antigen-specific T cell receptor (TCR) whilst retaining their phenotypic and suppressive function [19]
Initially the transduction efficiency was low, with only 0.05% of Tregs expressing mCherry, these cells (B6s-NIS Tregs) were expanded with autologous DCs and IL-2 and subsequently enriched for mCherry expression by flow cytometry cell sorting to achieve a population of cells that was 96% positive for mCherry expression (Fig. 1A). These B6s-NIS Tregs expressed similar levels of CD4, CD25 and FoxP3 compared to their non-transduced (B6s Tregs) counterparts (Fig. 1B) as well as maintaining their suppressive capacity (Fig. 1C). These observations suggested that retroviral administration of NIS and mCherry genes to CD4+CD25+FoxP3+ T cells and subsequent expansion did not alter their phenotype and suppressive function
Summary
Regulatory T cells (Tregs) are key players in the adaptive immune system. Tregs are responsible for maintaining immune homeostasis and self-tolerance by preventing autoimmunity and limiting immune responses to foreign antigens such as alloantigens [1]. The regulatory function of Tregs on CD4+ or CD8+ effector T cells (Teff) has made them a potential immunotherapy agent for clinical treatments of various diseases [2]. Adoptive transfer of murine derived Tregs has been a successful strategy in the prevention of graft rejection and in the cure of autoimmune diseases such as diabetes. Injection of ex-vivo expanded Tregs has been used in clinical trials to prevent Graft versus Host Disease (GvHD) in bone marrow transplant patients [6]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
