Atypical chemokine receptors (ACKRs) are regulators of leukocyte traffic, inflammation, and immunity. ACKR2 is a scavenger for most inflammatory CC chemokines and is a negative regulator of inflammation. Here we report that ACKR2 is expressed in hematopoietic precursors and downregulated during myeloid differentiation. Genetic inactivation of ACKR2 results in increased levels of inflammatory chemokine receptors and release from the bone marrow of neutrophils with increased anti-metastatic activity. In a model of NeuT-driven primary mammary carcinogenesis ACKR2 deficiency is associated with increased primary tumor growth and protection against metastasis. ACKR2 deficiency results in neutrophil-mediated protection against metastasis in mice orthotopically transplanted with 4T1 mammary carcinoma and intravenously injected with B16F10 melanoma cell lines. Thus, ACKR2 is a key regulator (checkpoint) of mouse myeloid differentiation and function and its targeting unleashes the anti-metastatic activity of neutrophils in mice.

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The lymphatic system plays an important role in the induction of the immune response by transporting antigens, inflammatory mediators, and leukocytes from peripheral tissues to draining lymph nodes. It is emerging that lymphatic endothelial cells (LECs) are playing an active role in this context via the expression of chemokines, inflammatory mediators promoting cell migration, and chemokine receptors. Particularly, LECs express atypical chemokine receptors (ACKRs), which are unable to promote conventional signaling and cell migration while they are involved in the regulation of chemokine availability. Here, we provide a summary of the data on the role of ACKR2 expressed by lymphatics, indicating an essential role for this ACKRs in the regulation of the inflammation and the immune response in different pathological conditions, including infection, allergy, and cancer.

Fibrosis is a progressive biological condition, leading to organ dysfunction in various clinical settings. Although fibroblasts and macrophages are known as key cellular players for fibrosis development, a comprehensive functional model that considers their interaction in the metabolic/immunologic context of fibrotic tissue has not been set up. Here we show, by transcriptome-based mathematical modeling in an in vitro system that represents macrophage-fibroblast interplay and reflects the functional effects of inflammation, hypoxia and the adaptive immune context, that irreversible fibrosis development is associated with specific combinations of metabolic and inflammatory cues. The in vitro signatures are in good alignment with transcriptomic profiles generated on laser captured glomeruli and cortical tubule-interstitial area, isolated from human transplanted kidneys with advanced stages of glomerulosclerosis and interstitial fibrosis/tubular atrophy, two clinically relevant conditions associated with organ failure in renal allografts. The model we describe here is validated on tissue based quantitative immune-phenotyping of biopsies from transplanted kidneys, demonstrating its feasibility. We conclude that the combination of in vitro and in silico modeling represents a powerful systems medicine approach to dissect fibrosis pathogenesis, applicable to specific pathological conditions, and develop coordinated targeted approaches.

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Fibrosis is a progressive biological process leading to organ dysfunction in different clinical settings. As fibroblasts and macrophages are known as key cellular players for fibrosis development, we adopted an in vitro model to define the functional effects of inflammation, hypoxia, and the adaptive immune context on their functional interplay with respect to fibrosis development. Transcriptomic analysis defined the impact of each parameter, acting alone or in combination, on functional properties of both cell types, exposed individually or in a cell-cell contact. These in vitro signatures were matched with transcriptomic profiles generated on laser-captured glomeruli and cortical tubulointerstitial area isolated from human transplanted kidneys with advanced stages of glomerulosclerosis and interstitial fibrosis/tubular atrophy, two clinically relevant conditions associated with organ failure in renal allografts. In vitro signatures were also used to instruct the development of a mathematical model predicting the relevance of each parameter in fibrosis development scenario, which indicated tolerance to inflammatory infiltrates under otherwise favorable conditions and defined an operative window in which hypoxia exerts a crucial role, supported by the degree of inflammation. Observed signatures and model-based predictions strongly suggested that irreversible fibrosis development is the result of specific combinations of metabolic and inflammatory cues, which drive distinct profibrotic paths in the glomeruli and the tubulointerstitial compartments. These findings, which found confirmation in tissue-based quantitative immune-phenotyping of transplanted kidney biopsies, indicate that the combination of in vitro and in silico modeling represents a powerful systems medicine approach to dissect fibrosis pathogenesis and develop coordinated targeted approaches.

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