Immune-driven dry eye disease primarily affects women; the cause for this sex-specific prevalence is unknown. Polymorphonuclear neutrophils (PMN) have distinct phenotypes that drive inflammation but also regulate lymphocytes and are the rate-limiting cell for generating anti-inflammatory lipoxin A4 (LXA4). Estrogen regulates the LXA4 circuit to induce delayed female-specific wound healing in the cornea. However, the role of PMNs in dry eye disease remains unexplored. We discovered an LXA4-producing tissue PMN population in the corneal limbus, lacrimal glands, and cervical lymph nodes of healthy male and female mice. These tissue PMNs, unlike inflammatory PMNs, expressed a highly amplified LXA4 circuit and were sex-specifically regulated during immune-driven dry eye disease. Desiccating stress in females, unlike in males, triggered a remarkable decrease in lymph node PMN and LXA4 formation that remained depressed during dry eye disease. Depressed lymph node PMN and LXA4 in females correlated with an increase in effector T cells (Th1 and Th17), a decrease in regulatory T cells (Treg), and increased dry eye pathogenesis. Ab depletion of tissue PMN abrogated LXA4 formation in lymph nodes, as well as caused a marked increase in Th1 and Th17 cells and a decrease in Tregs. To establish an immune-regulatory role for PMN-derived LXA4 in dry eye, females were treated with LXA4. LXA4 treatment markedly inhibited Th1 and Th17 and amplified Treg in draining lymph nodes, while reducing dry eye pathogenesis. These results identify female-specific regulation of LXA4-producing tissue PMN as a potential key factor in aberrant effector T cell activation and initiation of immune-driven dry eye disease.

Recently identified regulatory PMN control immune-driven dry eye disease (DED) in females by producing the arachidonic acid (ω-6)-derived specialized pro-resolving mediator (SPM), LXA₄, in lymph nodes. Dietary ω-3 docosahexaenoic acid (DHA) is protective in DED but mechanisms of action remain elusive. DHA is converted to ω-3 SPMs by PMN via the same lipoxygenases (LOX) that generate LXA₄. We investigated if dietary DHA amplifies SPM formation and affects T effector cell function and/or regulatory PMN in DED. DED was induced in mice on a DHA-enriched or ω-3-deficient diet. DHA deficiency amplified DED with marked sex-specific differences. Dietary DHA protection against dry eye disease correlated with increased PMN levels in lymph nodes, ocular tissues, and unexpectedly, selective amplification of LXA₄ tissue levels. Dietary DHA increased 12/15-LOX and decreased 5-LOX expression in lymph nodes and isolated lymph node PMN, which correlated with amplified LXA₄ formation. Acute DHA treatment rescued DHA-deficient females from exaggerated DED by amplifying lymph node LXA₄ formation, increasing T_reg and decreasing T_H1 and T_H17 effector cells. Our results identify DHA regulation of LXA₄ producing PMN in ocular tissues and lymph nodes in health and immune disease as novel mechanism and determinant for T-cell responses to routine ocular injury or stress signals.

Few patients with triple negative breast cancer (TNBC) benefit from immune checkpoint inhibitors with complete and durable remissions being quite rare. Oncogenes can regulate tumor immune infiltration, however whether oncogenes dictate diminished response to immunotherapy and whether these effects are reversible remains poorly understood. Here, we report that TNBCs with elevated MYC expression are resistant to immune checkpoint inhibitor therapy. Using mouse models and patient data, we show that MYC signaling is associated with low tumor cell PD-L1, low overall immune cell infiltration, and low tumor cell MHC-I expression. Restoring interferon signaling in the tumor increases MHC-I expression. By combining a TLR9 agonist and an agonistic antibody against OX40 with anti-PD-L1, mice experience tumor regression and are protected from new TNBC tumor outgrowth. Our findings demonstrate that MYC-dependent immune evasion is reversible and druggable, and when strategically targeted, may improve outcomes for patients treated with immune checkpoint inhibitors.