Low Immunogenic Profile Research Articles

Abstract 1021: In Vivo Immune Response To Allogeneic Porcine Mesenchymal Stem Cell (msc) Transplantation: A 12-day Course Of Fk-506 Abbrogates Humoral Response.

Purpose Several reports have highlighted the low immunogenic profile of MSCs. Therefore, we decided to test in vivo the humoral response to allogeneic MSCs transplantation and the effect of transient immunosuppression in a porcine model. Methods/Material MHC-controlled mini-swine SLA cd and SLA dd were used as donor and recipients, respectively. Two sites of transplantation were selected: subcutaneous and intracardiac. In our control group (n = 5), animals received no immunosuppression. In the study group (n = 11), nearly 1 x 10 6 allogeneic MSC/kg were injected. FK-506 was given from day 0 –12 and adjusted to therapeutic blood levels. Sera were serially collected up to one year after transplantation. The presence of specific anti-donor IgM and IgG was tested by flow cytometry and by a complement-mediated cytotoxicity assay. Results In the control group, all animals developed humoral responses in both IgM/G classes that persisted up to ten weeks. When transplanted subcutaneously, a single injection failed to elicit a complement-mediated cytotoxic response but subsequent re-challenge did. In the study group, only 2/11 FK-treated animals developed a transient humoral response, both in IgM and IgG, whereas all others failed to develop donor-specific antibodies. However, none of the sera tested from those 11 animals could elicit a complement-mediated cytotoxic response. Conclusion Allogeneic MSCs injected subcutaneously or intra-cardially can elicit prolonged humoral responses despite their putative low immunogenic profile. As already shown for experimental allogeneic organ transplantation, a transient immunosuppressive regimen can overcome the initial B cell response. Our result suggests that in vitro and in vivo characteristics of MSCs might differ and emphasizes the importance of pursuing research on allogeneic stem cell transplantation.

Although Pig Allogeneic Mesenchymal Stem Cells Are Not Immunogenic In Vitro, Intracardiac Injection Elicits an Immune Response In Vivo

In vitro, mesenchymal stem cells (MSCs) have demonstrated a low immunogenic profile. In this study, we tested the immune response to allogeneic MSCs in immunocompetent swines both in vitro and in vivo. Major histocompatibility complex-controlled swine leukocyte antigen (SLA) and SLA were used as donor and recipient, respectively. In vitro, proliferative responses were tested by mixed lymphocyte reaction (MLR) or cocultures and cytokine profiling by enzyme-linked immunosorbent assay. In vivo, allogeneic MSCs were injected in cardiac infarcted area (n=3) and compared with subcutaneous injections of either MSCs (n=2) or peripheral blood mononuclear cells (PBMCs; n=2). Two additional animals received a skin graft as controls. No immunosuppression was used. Specific antidonor humoral responses were tested by flow cytometry and complement-dependent cytotoxicity assay. In vitro, either unstimulated MSCs or interferon (IFN)-gamma stimulated MSC failed to elicit a proliferative response (stimulation index: 1.23 vs. 1.12 vs. 36.9 for controls, P<.001). Concomitantly to the absence of proliferation to MSCs, low production of IFN-gamma and interleukin-2 was evidenced in supernatants while the production of Th2 cytokines was comparable to controls. In vivo, all animals receiving skin grafts, subcutaneous PBMCs and intracardiac MSCs injections developed donor-specific cellular and humoral responses (immunoglobulins M and G) with antibody-complement-mediated cytotoxicity. Subcutaneous MSCs injection needed a rechallenge to similarly develop a cytotoxic humoral response. Intracardiac allogeneic porcine mesenchymal stem cells elicit an immune response despite their low immunogenic profile in vitro. This result suggests that in vivo characteristics of allogeneic MSCs might differ and emphasizes the importance of pursuing research both in vitro and in vivo.