Distinct Myeloid Cell Subsets Research Articles

Development of LT-HSC-Reconstituted Non-Irradiated NBSGW Mice for the Study of Human Hematopoiesis In Vivo.

Humanized immune system (HIS) mouse models are useful tools for the in vivo investigation of human hematopoiesis. However, the majority of HIS models currently in use are biased towards lymphocyte development and fail to support long-term multilineage leucocytes and erythrocytes. Those that achieve successful multilineage reconstitution often require preconditioning steps which are expensive, cause animal morbidity, are technically demanding, and poorly reproducible. In this study, we address this challenge by using HSPC-NBSGW mice, in which NOD,B6.SCID IL-2rγ -/-KitW41/W41 (NBSGW) mice are engrafted with human CD133+ hematopoietic stem and progenitor cells (HSPCs) without the need for preconditioning by sublethal irradiation. These HSPCs are enriched in long-term hematopoietic stem cells (LT-HSCs), while NBSGW mice are permissive to human hematopoietic stem cell (HSC) engraftment, thus reducing the cell number required for successful HIS development. B cells reconstitute with the greatest efficiency, including mature B cells capable of class-switching following allogeneic stimulation and, within lymphoid organs and peripheral blood, T cells at a spectrum of stages of maturation. In the thymus, human thymocytes are identified at all major stages of development. Phenotypically distinct subsets of myeloid cells, including dendritic cells and mature monocytes, engraft to a variable degree in the bone marrow and spleen, and circulate in peripheral blood. Finally, we observe human erythrocytes which persist in the periphery at high levels following macrophage clearance. The HSPC-NBSGW model therefore provides a useful platform for the study of human hematological and immunological processes and pathologies.

Abstract A25: Using biomaterial scaffolds to study the genesis of the immunosuppressive premetastatic niche in pancreatic cancer

Abstract Pancreatic cancer is a lethal malignancy with a 5-year survival rate of less than 10%. This poor prognosis is, in part, due to patients most often presenting with already metastatic disease. Pancreatic cancer is characterized by an abundant, reactive fibroinflammatory stroma, consisting of cancer-associated fibroblasts (CAFs) and infiltrating immune cells that send and receive signals to and from other nearby cells, including the tumor cells. The crosstalk between tumor cells and elements of the stroma results in an immunosuppressive tumor microenvironment both at the primary tumor and the sites of metastases. A key limitation in studying metastatic disease in mouse models is the inability to predict when the cancer cells will ultimately metastasize. In this study biomaterial scaffolds that mimic the premetastatic niche in vivo, by attracting immune cells followed by tumor cells, were used to longitudinally follow the metastasis process in individual animals. Biomaterial scaffolds were implanted subcutaneously to mimic the premetastatic niche in both syngeneic and spontaneous mouse (iKras* p53*) models of pancreatic cancer. Scaffolds were harvested 21 days post implantation and taken for histologic analysis to characterize the cellular infiltrate in response to the primary tumor. Histologic analysis (H&E, Gomori’s trichrome, and multiplex IHC) shows tumor cell colonization in the scaffold along with a robust immune and fibrotic response. To further characterize the scaffold infiltrate in control versus tumor-bearing mice, mass cytometry (CyTOF) and single-cell RNA sequencing (scRNA seq) analysis was performed. CyTOF analysis revealed the most abundant cell population is heterogenous myeloid cells, which are immunosuppressive in nature. Scaffolds from tumor-bearing animals have an increase in fibroblasts, and subsequently have fewer cytotoxic, CD8+ T cells. scRNA seq analysis of the scaffold infiltrate reveals CD8+ T cells from tumor-bearing animals express higher levels of the immune checkpoint, programmed cell death protein 1 (PD-1) and lower levels of the functional markers, perforin 1 and granzyme B, suggesting the CD8+ T cells are unable to perform their cytotoxic functions. Further analysis revealed a chemokine signaling axis, where fibroblasts recruit distinct subsets of myeloid cells. Taken together, the premetastatic niche (recapitulated by the biomaterial scaffolds) in pancreatic cancer has a high abundance of immunosuppressive myeloid cells, an increase in fibroblasts, and fewer CD8+ T cells, creating an immunosuppressive niche that allows for tumor cell colonization and growth. Future directions include blocking myeloid cell chemotaxis to the scaffold to prevent tumor cell dissemination and reduce metastatic burden. Citation Format: Samantha Kemp, Nina Steele, Eileen Carpenter, Veerin Sirihorachai, Grace Bushnell, Aaron Morris, Carlos Espinoza, Fatima Lima, Zeribe Nwosu, Sophia Orbach, Lonnie Shea, Filip Bednar, Howard Crawford, Marina Pasca di Magliano. Using biomaterial scaffolds to study the genesis of the immunosuppressive premetastatic niche in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr A25.

Secondary damage or viral infection following mild traumatic brain injury impedes tissue repair induced by distinct myeloid cell subsets

Abstract Mild traumatic brain injury (mTBI) causes severe meningeal cell death and vascular injury, leading to a robust peripheral immune response featuring neutrophils and monocytes/macrophages. Complications such as repetitive head injuries or viral infections following mTBI have the potential to significantly alter the immune response and impact wound repair. Using a closed-skull compression model of mTBI, we found that meningeal vasculature can regenerate within 7 days of injury, coinciding with a dynamic, bifurcated myeloid cell response. Macrophages derived from inflammatory monocytes scavenged dead cells while non-classical monocyte-derived macrophages promoted angiogenesis. The CD206+ angiogenic macrophages were positioned around the lesion perimeter where they aided in fibrinogen clearance and matrix remodeling. A peripheral infection by lymphocytic choriomeningitis virus (LCMV) during peak vascular damage delayed wound repair and promoted a significant meningeal CD8+ T cell response. The infected environment also shifted the myeloid cells to a more inflammatory state, reducing the amount of CD206+ macrophages around the lesion. Interestingly, we found that a secondary injury also interrupted wound repair only when experienced during the acute “inflammatory” but not the “wound-healing” phase. In fact, the mTBI lesion and infiltrating macrophages were resistant to further damage when reinjured during the wound-healing phase. Our findings demonstrate that meningeal vasculature can undergo robust regeneration following mTBI orchestrated by distinct myeloid cell populations. However, this wound repair process can be significantly disrupted by both sterile and viral insults following the initial injury.

Two Distinct Myeloid Subsets at the Term Human Fetal-Maternal Interface.

During pregnancy, immune cells infiltrate the placenta at different stages of fetal development. NK cells and macrophages are the most predominant cell types. These immune cells play pleiotropic roles, as they control spiral artery remodeling to ensure appropriate blood supply and maintain long-term tolerance to a true allograft; yet, they must be able to mount appropriate immune defenses to pathogens that may threaten the fetus. Whether the same cell type accomplishes all these tasks or if there are dedicated subsets remains controversial. Here, we identify and characterize two distinct subsets of myeloid cells that differ in their pro-inflammatory/regulatory capacity. While one subset predominantly produces the immune-modulating cytokine IL-10, the second subset has superior capacity to secrete pro-inflammatory mediators, such as IL-1β and IL-6. The putative regulatory myeloid cells also express high levels of inhibitory receptors and their ligands, including programmed cell death 1 (PD1) ligands. Importantly, a large fraction of CD8 and CD4 cells in normal term human placenta are PD1 positive, suggesting that the PD1/PD1 ligands axis might be critical to maintain tolerance during pregnancy.

Abstract 3021: CCR5 inhibition: macrophage repolarization therapy for colorectal cancer

Abstract In patients with metastatic colorectal cancer (CRC), the local immune response influences the clinical course. An in-depth analysis of the invasive margin of human CRC liver metastases revealed a distinct immunological microenvironment. Within this microenvironment, two distinct subsets of myeloid cells induce an influx of T cells into the invasive margin via CXCL9/CXCL10. CCL5 is produced by these T cells and stimulates pro-tumoral effects via CCR5, creating an exploitive loop. CCR5 was found on macrophages, lymphocytes and on the vast majority of tumor cells. Inhibition of CCR5 in patient-derived functional in vitro organotypic culture models showed a promising macrophage repolarization with anti-tumoral effects. These effects are mediated by activation of an antiviral program in macrophages, leading to interferon and reactive oxygen species production and subsequent selective tumor cell death. These anti-tumoral effects were confirmed in a phase I trial with a CCR5 antagonist in 14 patients with liver metastases of advanced refractory CRC. Treatment with the oral CCR5 Inhibitor was very well tolerated and objective responses were seen, especially in combination with previously ineffective chemotherapy. Biopsies revealed mitigation of tumor-promoting inflammation within the tumor tissue, confirming the validity of the explant model and highlighting the feasbility of this approach. It furthermore shows the proof-of-concept for macrophage repolarization in cancer patients. Citation Format: Niels Halama, Inka Zoernig, Anna Berthel, Christoph Kahlert, Fee Klupp, Meggy Suarez-Carmona, Karsten Brand, Juergen Krauss, Felix Lasitschka, Alexis Ulrich, Juergen Weitz, Martin Schneider, Markus Buechler, Laurence Zitvogel, Thomas Herrmann, Axel Benner, Christina Kunz, Stephan Luecke, Christoph Springfeld, Christine S. Falk, Dirk Jaeger. CCR5 inhibition: macrophage repolarization therapy for colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3021. doi:10.1158/1538-7445.AM2017-3021

Abstract B037: Macrophage repolarization therapy in metastatic colorectal cancer: CCR5 inhibition

Abstract The influence of the local immune response on the clinical course of colorectal cancer (CRC) has been analyzed extensively. Analyzing the invasive margin of human CRC liver metastases, we identified a protumoral mechanism of T-cell-derived CCL5 that leads to immune cell exploitation by tumor cells. Two distinct subsets of myeloid cells produce CXCL9/CXCL10, which induce an influx of T cells into the invasive margin. CCL5 is produced by these exhausted T cells and stimulates tumor cell proliferation and invasive behavior via CCR5 on tumor cells and macrophages. CCR5 inhibition in patient-derived functional in vitro organotypic culture models induced macrophage repolarization with anti-tumoral effects. These immunomodulatory and anti-tumoral effects of CCR5 blockade then could be confirmed in a phase I trial with a CCR5 antagonist in advanced refractory CRC patients with liver metastases. Amelioration of tumor-promoting inflammation on the tumor tissue level and objective tumor responses in advanced metastatic CRC patients were observed. Citation Format: Niels Halama, Inka Zoernig, Anna Berthel, Christoph Kahlert, Fee Klupp, Meggy Suarez-Carmona, Juergen Krauss, Karsten Brand, Felix Lasitschka, Tina Lerchl, Claudia Luckner-Minden, Alexis Ulrich, Juergen Weitz, Martin Schneider, Markus W. Buechler, Laurence Zitvogel, Thomas Herrmann, Axel Benner, Christina Kunz, Stephan Luecke, Christoph Springfeld, Christine Falk, Dirk Jaeger. Macrophage repolarization therapy in metastatic colorectal cancer: CCR5 inhibition [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B037.

Tumoral Immune Cell Exploitation in Colorectal Cancer Metastases Can Be Targeted Effectively by Anti-CCR5 Therapy in Cancer Patients

The immune response influences the clinical course of colorectal cancer (CRC). Analyzing the invasive margin of human CRC liver metastases, we identified a mechanism of immune cell exploitation by tumor cells. While two distinct subsets of myeloid cells induce an influx of T cells into the invasive margin via CXCL9/CXCL10, CCL5 is produced by these T cells and stimulates pro-tumoral effects via CCR5. CCR5 blockade in patient-derived functional in vitro organotypic culture models showed a macrophage repolarization with anti-tumoral effects. These anti-tumoral effects were then confirmed in a phase I trial with a CCR5 antagonist in patients with liver metastases of advanced refractory CRC. Mitigation of tumor-promoting inflammation within the tumor tissue and objective tumor responses in CRC were observed.

This Month in Gastroenterology

This Month in Gastroenterology