In vivo visualization of immune responses during rejection of allogeneic tissue in the anterior eye chamber

The anterior chamber of the eye (ACE) was recently described as a novel imaging site in diabetes research by observing transplanted pancreatic islet activity in the eye of a living animal. The ACE technology is ideally suited for non-invasive and longitudinal in vivo imaging. We take advantage of the ACE window to observe immune responses, especially allorejection of islet cells by cytotoxic T lymphocytes. We transplant pancreatic islets from DBA/1J mice into C57BL/6 recipient knock-in mouse which endogenously express a fluorescent protein (GzmB-mTFP or Bonzo) in T cells. We follow the onset of the rejection after vascularization on islets, when immune cells start to infiltrate into ACE, until the end of the rejection process where the islets are cleaned up for roughly a month by repetitive two-photon microscopy. We find that T cells show less migration velocity on islets of foreign mice than on autologous tissue, indicating T cell activation and recognition on the islets. Interestingly, the temporal infiltration pattern of T cells during the rejection process is precisely regulated, showing enrichment of CD4+ T cells on the islets before arrival of CD8+ T cells in histological studies. We use the ACE platform as a more comprehensive environment to study immune response and focus on T cell killing. We aim to understand the mechanism and regulation of T cell-mediated killing in vivo and to further investigate the killing in gene-deficient mice (i.e. munc13-4 and perforin) that resemble to severe human immune disease.