Hsp70, originally described as a warmth induced protein[1], is the most conserved of Hsps, and currently known to have immunomodulatory properties. Finally, TBHsp70 inhibited pores and skin allograft acute rejection, and depletion of Tregs using a monoclonal antibody completely abolished this effect. == Conclusions/Significance == We present the 1st evidence for an immunosuppressive part for this protein inside a graft rejection system, using an innovative approach immersion of the graft cells in TBHsp70 remedy instead of protein injection. Also, this is the first study that demonstrates dependence on Treg cells for the immunosuppressive part of TBHsp70. This getting is relevant for the elucidation of the immunomodulatory mechanism of TBHsp70. We propose that this protein Shikimic acid (Shikimate) can be used not only for chronic inflammatory diseases, but is also useful for organ transplantation management. == Intro == Heat shock proteins (Hsp) are highly immunogenic proteins, though conserved between mammals and microorganisms. Hsp70, originally described as a warmth induced protein[1], is the most conserved of Hsps, and currently known to have immunomodulatory properties. However, the exact mechanisms through which it exerts this effect are not completely obvious[2].Mycobacterium tuberculosisHsp70 (TBHsp70) has been shown to protect from induced arthritis in rats[3],[4],[5]. We have shown that TBHsp70 induces IL-10 production by monocytes and synovial cells of arthritis patients, leading to a reduction of TNF- e IFN- levels[6]. Also, we observed that TBHsp70 can inhibit differentiation of bone marrow derived dendritic cells (BMDCs)in vitro, leading to the production of IL-10 by these cells[7]. It was suggested that exposure to bacterial Hsps Shikimic acid (Shikimate) could activate self Hsp-specific T cells that would be mix reactive with bacterial Hsps and result ER81 in immunoregulatory pathways[8]. More recently, inside a proteoglycan-induced arthritis model, Shikimic acid (Shikimate) TBHsp70 immunization showed a protecting potential that was dependent on IL-10[9]. In addition, the treatment with TBHsp70 upregulated IL-10 mRNA in regulatory T cells (Tregs). Treg cells are crucial for the suppression of acute rejection in allografts[10]. These cells develop in the thymus or can be induced in peripheral sites when given appropriate signals from the antigen showing cells. They may be CD25+, and Shikimic acid (Shikimate) also express the transcriptional element forkhead package 3 (FoxP3), cytotoxic T-lymphocyte antigen 4 (CTLA-4) and glucocorticoid-induced tumor necrosis element receptor (GITR)[11]. They can suppress inflammatory reactions by regulating the activity of self-reactive standard T cells. Tregs produce IL-10 and TGF- and actively suppress non-Treg proliferation[12]. They have been shown to be important for inhibition of allograft rejection in several models[13],[14]. In this study, we investigated whether TBHsp70 could act as an immunosuppressant in two allograft rejection systems. We also investigated if treatment with this protein would induce Treg cells. Our results suggest that TBHsp70 is definitely capable of delaying acute allograft rejection, and this response is definitely mediated by Tregs. == Results == == TBHsp70 suppresses tumor allograft rejection == We asked if TBHsp70 could inhibit allograft rejection in two different models. We 1st used a transplanted allogeneic tumor model, injecting BALB/c mice (H-2d) with B16F10 melanoma cells (H-2b). Cells were resuspended in PBS comprising TBHsp70 or no stimulus and were injected subcutaneously in mice. Tumor growth was recorded daily for 12 days. Around day time 6 after injection, PBS-injected mice completely declined the tumor cells, and the progressive elimination of the dark area occupied by melanoma cells Shikimic acid (Shikimate) could be observed in the injection site (Fig. 1A). However, mice that received tumor cells with TBHsp70 not only did not reject the tumor (Fig. 1A), but also allowed tumor growth through the 12-day time period (Fig. 1B). These results suggested that TBHsp70 could inhibit tumor allograft rejection, assisting the immunosuppressive potential that had been previously observed in arthritis models[3],[4],[15],[16]. == Number 1. B16F10 tumor allograft in BALB/c mice. == (A) Standard aspect of injection site in mice treated subcutaneously with tumor cells in PBS comprising TBHsp70 or PBS only on day time 12 after transplant of tumor cells. (B) Sequential measurements of tumor diameter. n = 3 mice per treatment group. This experiment was performed seven instances, with identical results. ***, p<0.0001. == T cells with regulatory phenotype.