IMMUNE REGULATION AND TOLERANCE I

M. Himmel¹, S. Crome², S. Ivison², T. Steiner², M.K. Levings^3
1Surgery, University of British Columbia, Vancouver/BC/CANADA, ², University of British Columbia, Vancouver/CANADA, ³Department Of Surgery, Vancouver Coastal Health Research Institute and University of British Columbia, Vancouver/CANADA

Body: Introduction: T regulatory cells (Tregs) play a key role in establishing and maintaining tolerance to self and foreign antigens. If Tregs are lost through genetic or environmental factors,dysregulated immune responses can lead to diseases such as diabetes, rheumatoid arthritis, or inflammatory bowel disease. On the other hand, replacing or enhancing Tregs can restore immunehomeostasis, prevent autoimmunity, and facilitate long-term acceptance of foreign cells or tissues. Tregs are well equipped to rapidly travel to sites of inflammation, and indeed inflamed tissuesoften have significant numbers of these cells. We are interested in defining why Tregs arrive in inflamed tissues prior to other adaptive immune cells in order to better understand their biologicalfunction and to ultimately optimize cell-therapy based methods to induce transplantation tolerance. One hypothesis regarding how Tregs normally function is that they may have the ability to producechemokines that attract innate immune cells which could rapidly resolve inflammation prior to eliciting adaptive immune cells. Methods and Results: To determine whether Tregs produce differentchemokines, CD4+CD25hi Treg cells were isolated by flow cytometry and stimulated under different conditions. Surprisingly we found that Tregs make significant amounts of inflammatory acute phasechemokines, including Interleukin-8 (IL-8), a chemokine which binds to the IL-8 receptors CXCR1 or CXCR2 and attracts neutrophils to sites of inflammation. The ability of Tregs to produce IL-8 wasfurther confirmed by stimulating ex vivo CD4+ T cells and co-staining for CD4, CD25, FOXP3, and, IL-8. Transduction of CD4+ T cells with FOXP3 expressing lentivirus also resulted in an increase inIL-8 production, suggesting it is specifically FOXP3+ Tregs which make this inflammatory chemokine. Furthermore, these IL-8 producing Tregs do not produce IL-17 or IFN-g and are not restricted to theCD45RA+ or CD45RA- memory population. Neutrophil recruitment assays were used to demonstrate that Treg derived IL-8 does induce neutrophil chemotaxis. Conclusion: These results suggest that Tregs mayplay a role in the recruitment of innate inflammatory immune cells to sites of inflammation during the early stages of an immune response. With these findings, we aim to gain a better understandingof the role Tregs play in recruiting innate versus adaptive immune cells to sites of inflammation, with the goal of developing cellular based therapies to induce transplantation tolerance.

Disclosure: All authors have declared no conflicts of interest.