Exposure to ischemia-related neoepitopes exacerbates secondary ischemia–reperfusion injury in mice

Ischemia is a common clinical condition, characterized by reduced blood supply to tissues or organs owing to blockage or constriction of blood vessels. In this study, we hypothesized that the humoral immune response is activated by ischemia-related neoepitopes. Upon detection of these newly exposed or modified antigens, the immune system mounts a humoral response involving the production of specific antibodies. These antibodies may then contribute to amplification of the inflammatory cascade, ultimately exacerbating tissue damage during secondary ischemia–reperfusion (I/R) injury in mice. To test this hypothesis, we conducted a series of experiments using a well-established murine model of two sequential I/R injuries. Our findings indicated that the presence of these neoepitopes was associated with the formation of germinal center B cells and subsequent immunoglobulin isotype switching. Consequently, mice exhibited more severe tissue injury during the secondary I/R event, as demonstrated by greater histopathological damage and elevated serum enzyme levels (p < 0.05). Furthermore, administration of tacrolimus following the first I/R injury significantly attenuated secondary injury, reducing its severity to a level comparable to that observed during the primary event (p < 0.05). This intervention was also associated with a marked decrease in IgG and complement C4d deposition within the affected kidney (∼50% reduction). Collectively, these findings indicate the presence of neoepitopes and the humoral immune response they elicit, offering insights into the development of novel clinical interventions.