PD-1 Mediated Regulation of Salivary Gland Integrity - Abstract Immune checkpoints play an important role in restraining the immune response, maintaining self- tolerance and preventing excessive collateral damage. Immune checkpoint blockade has revolutionized cancer immunotherapy but can lead to immune related adverse events (IrAEs). Patients receiving programmed cell death protein 1 (PD-1) blockade can develop IrAEs including vitiligo, colitis, endocrinopathies, and Sicca Syndrome, an autoimmune disease characterized by the accumulation of immune cells in the salivary and lacrimal glands, leading to deterioration and dysfunction. After immune cell activation, PD-1 is upregulated, and upon interacting with its ligand PD-L1, PD-1 signaling results in reduced proliferation, cytokine production, and cytotoxicity. PD-1 is expressed on infiltrating lymphocytes of the salivary gland including natural killer (NK) and T cells. Hyporesponsive immune cells in the salivary gland are thought to retain the integrity of this delicate tissue, while inadvertently contributing to viral latency. While trying to understand why lymphocytes in this organ are hyporesponsive, I unexpectedly found that genetic loss of PD-1 results in increased CD8+ T cell number and frequency in the salivary glands of naïve animals. Additional preliminary data suggests that NK cells may control CD8+ T cell expansion in the salivary gland. Based on these data, I hypothesize that in order to preserve the integrity of the salivary gland, NK cells may control T cell proliferation via the PD-1/PD-L1 axis in this organ. Therefore, in Specific Aim 1, I will elucidate the molecular mechanism by which PD-1 regulates CD8+ T cells in the salivary gland, and characterize the transcriptome and effector functions of the expanded CD8+ T cell population. In Specific Aim 2, I will characterize the potential immunopathological consequences of CD8+ T cell expansion in the PD-1 KO salivary gland by assessing histopathology and saliva secretions. These studies of PD-1 on salivary gland immune cells should provide insights for prevention and treatments of IrAEs. In preparation for the proposed work, my training has taken place in the outstanding immunology laboratory of Dr. Laurent Brossay, as well as within the supportive Pathobiology Graduate Program. My training experience will be enriched by attending and presenting at national and international conferences, and thoughtful mentoring by my sponsor. Completion of this proposal will prepare me with a repertoire of skills and the key foundational knowledge required for a successful career as an independent researcher.
