Factors influencing the regulation of cytokine balance during islet transplantation in mice

Many experimental islet studies compare the effect of allogeneic transplantations with either syngeneically transplanted or sham-operated animals. Presently we examined multiple “control” treatments to be able to distinguish effects by the operating procedures themselves versus reactions induced by islet graft rejection. Herein, we have studied untreated, sham-operated, syngeneically or allogeneically (C57BL/6) islet transplanted BALB/c mice, and subsequently examined cytokine production (TNFα, IFNγ, IL-4, IL-10, IL-17 and TGF-β) in vitro by RT-PCR and ELISA in spleen cells and transplants. To investigate if the strain of the recipient mice influences cytokine production we also performed allogeneic islet transplantations in the reverse direction. So-called control treatments such as sham operations and syngeneic transplantations had a distinct effect on cytokines in spleen cells, possibly induced by surgery and/or anaesthesia. This seems to decrease the regulatory T cells, thereby leading to increased cytokine expression. Furthermore, spleen cells from surgically manipulated animals seem to have a decreased responsive capacity to con A stimulation in culture. Cytokine generation, FoxP3 mRNA expression and COX-2 mRNA expression in the two investigated mouse strains were sometimes altered in opposite directions by the treatments. In conclusion, the genetic background of both the islet donor and recipient has a major impact on both the magnitude and skewing of a cytokine response. Moreover, factors not directly related to allorejection influences systemic cytokine production in connection to islet transplantation.