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Objective To track superparamagnetic iron oxide (SPIO)-labeled pancreatic islet cells in rats using 3.0T magnetic resonance imaging (MRI), and to detect the survival and rejection of grafts after transplantation. Methods Twenty male Wistar rats and 5 male Lewis rats were included in the study. SPIO-labeled pancreatic islet cells were tracked using a GE 3.0T Signa Excite MRI scanner with an animal coil. The images of SPIO-labeled islet cells in rats after transplantation were compared with those of the unlabeled ones. FSE T2WI sequence and GRE T2*WI sequence were used for the detection. The sensitivity of images for detection of grafts was also compared. SPIO-labeled pancreatic islet cells isolated from Wistar and Lewis rats were transplanted into the liver of Wistar rats. Afterwards, the survival and rejection of islet cells were observed sequentially in these two growps. The rats in the syngeneic group were sacrificed 3 months post-transplantation, while the rats in the allogeneic group were sacrificed 3 weeks post-transplantation. MRI of the grafts were correlated with the pathological results. Results SPIO-labeled pancreatic islet cells were seen on MRI as distinct homogenous, hypointense spots in the liver. GRE T2*WI were more sensitive to the detection of SPIO-labeled islet cells than FSE T2WI. The relative count of hypointense spots in the syngeneic group were (90.03±9.52)%, (92.87±18.21)% and (86.25±24.81)%, respectively at 1 week, 2 weeks and 3 weeks after transplantation, while the relative count in the allogeneic group were (41.40±15.41)%, (33.41±14.01)% and (23.58±16.78)%, respectively. The difference between these counts was statistically significant (P<0.01). Iron particles were detected only in the SPIO-labeled cells. Three months post-transplantation, the grafts were found well-preserved in the liver of the rats of the syngeneic group, while only a few grafts were found in that of the allogeneic group. Conclusions MRI can be used to track SPIO-labeled islet cells in vivo, and has significant value in detecting the survival and rejection of grafts after transplantation in rats.
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Objective To investigate the possibility of inducing anergy by blocking the CD40/CD154 and B7/CD28 costimulatory pathways and the reversal condition of anergic cells. Methods Splenocyte proliferation in primary mixed lymphocyte reaction (MLR) consisting of BALB/c as responder and C3H as stimulator was measured by the addition of different levels of anti-CD154 and anti-CD80 monocolonal antibody (mAb). To test the reversal condition of anergic cells induced by combined anti-CD154 and anti-CD80 mAbs blocking, C3H or C57BL/6J spleenocytes were irradiated, or different concentrations of recombinant mouse interleukin-2 (rmIL-2), or both C3H splenocytes and rmIL-2 were added to the anergic cells. Results The proliferation of anergic cells treated with both mAbs in the primary MLR was strongly inhibited in a dose-dependent manner. The cells proliferated in response to third party (C57BL/6J) stimulator. The cells did not respond to original (C3H) stimulator, and they also failed to proliferated in response to the addition of exogenous IL-2. Furthermore, the anergic state was reversed by both original (C3H) stimulator and the addition of exogenous rmIL-2. Conclusion The blockade of CD40/CD154 and B7/CD28 costimulatory pathways induces alloantigen-specific anergy, and the anergic state can be reversed by both antigen restimulation and the addition of exogenous IL-2.