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Lymphatic Vessels: Enabling Defense on Two Fronts

By Christina Leah B. Kline, PhD

In a war, first-line troops are essential — such are resident memory T cells (TRM), standing guard at peripheral sites, ready to fight infections and cancer (1). In melanoma, skin TRMs have been observed in survivors up to nine years after positive responses to immunotherapy (2). More recently, it has been shown that TRMs were present not only in the skin but also in skin-draining lymph nodes (dLNs), keeping lymph node metastases at bay. The Laboratory for Lymphatic Immunobiology, led by 2022 AACR-Bristol Myers Squibb Midcareer Female Investigator Grant Recipient Amanda Lund, PhD, seeks to understand how transport of TRMs through lymphatic vessels helps facilitate these critical peripheral immune responses to antigen, whether presented by infectious agents or cancer cells. In their new manuscript, led by graduate student Taylor Heim, they showed how movement of TRMs out of the skin through lymphatic vessels is critical in anti-viral immune memory (3).

Amanda Lund, PhD

Dr. Lund’s team used vaccinia virus (VV) to model skin infection by scarification in mice, where viable virus is confined to the initial site of infection (4). Given the restricted pattern of infection, any adaptive immune responses seen in the skin-draining lymph nodes can be attributed to lymphatic transport. Numerically similar levels of TRMs were observed in skin and dLNs. Results from various experiments on another mouse model (K14-V3 mice), which do not form dermal lymphatic vessels (5), collectively demonstrated that the establishment of TRMs in the lymph node depends on lymphatic transport between the skin and the dLNs.

To directly test the hypothesis that skin TRMs are the precursors of the TRMs in the lymph node, the researchers depleted T cells from circulation except for in the skin, after antigen exposure. Despite this ablation, TRM numbers in the skin and dLNs were not affected. In another experiment, they resected the ear skin of their VV mouse model at 5-, 13-, or 20-days post-infection. They observed that when the infected skin was removed 5 days after infection, a significant decrease in TRMs in lymph nodes was observed. Furthermore, they saw that abundance of TRMs in the lymph nodes correlated with the available time for T cell transit from skin to the dLN. Results of these studiessuggest that T cell egress from the skin is necessary and sufficient for dLN formation after VV infection.

To begin to understand the roles of the TRMs in the lymph node, scRNA-seq was performed on dLN T cells 45 days post-infection.  Differential gene expression analysis revealed that transcripts of genes associated with TCR signaling and cytotoxicity tended to be more highly expressed in the TRMs than in circulating memory T cells. They showed that these dLN TRMs were equipped to stave off new viral infection.

Underscoring the implication of this work, Dr. Lund shared: “these results help demonstrate that the status of the lymphatic vasculature might program the potential for future responses to challenge – this could be a second viral encounter, or in the setting of cancer, regional recurrence. Our ongoing efforts funded by this grant expand these ideas to melanoma to understand how the effects of a tumor on the associated lymphatic vasculature and lymph node might disrupt the establishment of potent memory and thereby facilitate metastasis.”

In acknowledging the impact of the AACR grant on her work, she emphasized, “Receiving the AACR-Bristol Myers Squibb Midcareer Female Investigator Grant has accelerated our efforts to investigate mechanisms at the interface of anti-tumor CD8+ T cell effector function and lymphatic vessel biology. We are building a systems level view for how the T cell response is set and reset over time during tumor progression. Through this work, we have expanded our grant portfolio (new multiple PI R01 and multiple pending applications) and experimental tool set to dissect the contribution of lymphatic transport and lymph nodes to cancer immunotherapy. Importantly, this funding and the work that it supported was a critical component of my successful tenure application and I am thrilled to have the opportunity to continue to tackle these important questions.”

References:

  1. Malik BT, Byrne KT, Vella JL, Zhang P, Shabaneh TB, Steinberg SM, Molodstov AK, et al. Resident memory T cells in the skin mediate durable immunity to melanoma. Science Immunol 2017; 2: eaam6346
  2. Han J, Zhao Y, Shirai K, Molodtsov A, Kolling FW, Fisher JL, et al. Resident and circulating memory T cells persist for years in melanoma patients with durable responses to immunotherapy. Nat Cancer 2021; 2:300-311
  3. Heim TA, Schultz AC, Delclaux I, Cristaldi V, Churchill MJ, Ventre KS, et al. Lymphatic vessel transit seeds cytotoxic resident memory T cells in skin draining lymph nodes. Sci. Immunol 2024; 9: eadk8141
  4. Loo CP, Nelson NA, Lane RS, Booth JL, Loprinzi Hardin SC, Thomas A, et al. Lymphatic vessels balance viral dissemination and immune activation following cutaneous viral infection. Cell Rep 2017; 20:3176-318
  5. Mäkinen T, Jussila L, Veikkola T, Karpanen T, Kettunen MI, Pulkkanen KJ, et al. Inhibition of lymphangiogenesis with resulting lymphedema in transgenic mice expressing soluble VEGF receptor-3. Nat Med 2001; 7:199-205 Khan TN, Mooster JL, Kilgore AM, Osborn JF, Nolz JC. Local antigen in nonlymphoid tissue promotes resident memory CD8+ T cell formation during viral infection. J Exp Med 2016; 213:951-66