Mohannad Alkhatib

Adoptive transfer of cells, often expressing green fluorescent protein (GFP) is an increasingly common method of treating certain diseases and studying immunology. However, in both cases, GFP has the potential to be recognized as a foreign protein by the recipient's immune system leading to the rejection of the cells. Despite this immunogenic potential, GFP rejection is not well documented in the literature. To further characterize this rejection, equal numbers of GFP+ or GFP- cells expressing non-immunogenic identification markers were transferred into Non-Obese Diabetic (NOD) mice, immunodeficient mice, and mice possessing the GFP gene. The ratio of surviving GFP+ and GFP- cells in these mice was later quantified using flow cytometry. Established methods to induce tolerance were also used to prevent rejection. This model allowed us to demonstrate that GFP rejection leads to the death of almost all transferred GFP+ cells in less than a few days, and this effect is not seen in immunodeficient mice or mice expressing the GFP transgene. However, we were not able to prevent the rejection in immunocompetent mice using known tolerance mechanisms. Ultimately, we demonstrated that GFP rejection is remarkably potent in NOD mice, but further studies should use knock-out mice to ascertain what cell types are necessary for GFP rejection.