Exploration of Conditions Affecting Cytokine Production in Experimental Type 1 Diabetes Mellitus

Cytokines are soluble signalling mediators within the immune system, and have been shown to be of importance in the development of type 1 diabetes (T1D). This thesis studied the production of cytokines in experimental models of T1D and during transplantation of insulin-producing islets of Langerhans. We have demonstrated that the transcriptional TNFα-inhibitor MDL 201,449A, previously shown to reduce immune-mediated diabetes induced in mice by multiple low doses of streptozotocin, was not TNFα-specific, but also inhibited IFNγ and IL-10 in spleen cells. Furthermore, when the inhibitor was removed from in vitro cultures, a rebound phenomenon of increased cytokine secretion occurred. The thesis also investigated whether plastic adhesion, a method generally employed to deplete macrophages, influenced cytokine production in spleen cells. We observed that plastic adhesion increased TNFα, IFNγ and IL-10 release, and decreased IL-4 secretion. Plastic adhesion depleted only ~30% of the macrophages, but as much as ~60% of the regulatory T cells. Thirdly, we found that “control” treatments for islet transplantations, i.e. syngeneic and sham transplantations, exerted a clear effect on cytokine production from spleen cells, possibly due to a decrease in regulatory T cells that may be caused by the surgery and/or anaesthesia. Moreover, spleen cells from mice exposed to surgery exhibited a decreased proliferative capacity to concanavalin A stimulation. We also perceived a marked difference in cytokine response depending on the mouse strain used in the experiments. Finally, we aimed to elucidate if, besides autoimmune activities, also high glucose- and free fatty acid concentrations as seen in diabetes could cause changes in cytokine production. We observed that spleen cells cultured in varying glucose concentrations had different cytokine production profiles. The free fatty acid palmitate might also influence cytokine release, but this effect was obscured by the cytokine-suppressive action of the ethanol used to dissolve the palmitate