Mechanisms of immune suppression in peripheral tissues counteract protective immunity to prevent immunopathology and are co-opted by tumors for immune escape. Nonhematopoietic cells, as the resident tissue scaffold, play critical roles in regulating the infiltration, retention, function, and exit of tissue- and tumor-infiltrating leukocytes. While lymphatic vessels facilitate T-cell priming through dendritic cell and antigen delivery to lymph nodes, they also facilitate regional metastasis and exert multiple immune-suppressive mechanisms that maintain peripheral tolerance in steady state lymph nodes. We hypothesized that in tumors peripheral lymphatic vessels exhibit context-dependent function that limits local effector CD8+ T-cell accumulation in melanoma. Our work demonstrates that lymphatic vessels both maintain homeostatic mechanisms of peripheral tolerance in poorly inflamed tumors to limit immune surveillance and activate mechanisms of adaptive immune resistance in the context of potent cytotoxic T-cell activity. Consequently, we present tumor-associated lymphatic vessels as a new, anatomic immune checkpoint in melanoma. Our work suggests that understanding context-dependent lymphatic vessel function will continue to reveal novel mechanisms of immune control and metastasis that may be targeted for therapeutic response.
Citation Format: Amanda W. Lund. Lymphatic vessels: Barriers to adaptive immunity in melanoma [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr IA19.