Identification of a non-canonical chemokine-receptor pathway suppressing regulatory T cells to drive atherosclerosis.

CCL17 is produced by conventional dendritic cells (cDCs), signals through CCR4 on regulatory T cells (Tregs), and drives atherosclerosis by suppressing Treg functions through yet undefined mechanisms. Here we show that cDCs from CCL17-deficient mice display a pro-tolerogenic phenotype and transcriptome that is not phenocopied in mice lacking its cognate receptor CCR4. In the plasma of CCL17-deficient mice, CCL3 was the only decreased cytokine/chemokine. We found that CCL17 signaled through CCR8 as an alternate high-affinity receptor, which induced CCL3 expression and suppressed Treg functions in the absence of CCR4. Genetic ablation of CCL3 and CCR8 in CD4+ T cells reduced CCL3 secretion, boosted FoxP3+ Treg numbers, and limited atherosclerosis. Conversely, CCL3 administration exacerbated atherosclerosis and restrained Treg differentiation. In symptomatic versus asymptomatic human carotid atheroma, CCL3 expression was increased, while FoxP3 expression was reduced. Together, we identified a non-canonical chemokine pathway whereby CCL17 interacts with CCR8 to yield a CCL3-dependent suppression of atheroprotective Tregs.

ILC2-mediated immune crosstalk in chronic (vascular) inflammation.

Crosstalk between innate and adaptive immunity is pivotal for an efficient immune response and to maintain immune homeostasis under steady state conditions. As part of the innate immune system, type 2 innate lymphoid cells (ILC2s) have emerged as new important regulators of tissue homeostasis and repair by fine-tuning innate-adaptive immune cell crosstalk. ILC2s mediate either pro- or anti-inflammatory immune responses in a context dependent manner. Inflammation has proven to be a key driver of atherosclerosis, resembling the key underlying pathophysiology of cardiovascular disease (CVD). Notably, numerous studies point towards an atheroprotective role of ILC2s e.g., by mediating secretion of type-II cytokines (IL-5, IL-13, IL-9). Boosting these protective responses may be suitable for promising future therapy, although these protective cues are currently incompletely understood. Additionally, little is known about the mechanisms by which chemokine/chemokine receptor signaling shapes ILC2 functions in vascular inflammation and atherosclerosis. Hence, this review will focus on the latest findings regarding the protective and chemokine/chemokine receptor guided interplay between ILC2s and other immune cells like T and B cells, dendritic cells and macrophages in atherosclerosis. Further, we will elaborate on potential therapeutic implications which result or could be distilled from the dialogue of ILC2s with cells of the immune system in cardiovascular diseases.

Advances in Human Immune System Mouse Models for Personalized Treg-Based Immunotherapies.

Immunodeficient mice engrafted with a functional human immune system [Human immune system (HIS) mice] have paved the way to major advances for personalized medicine and translation of immune-based therapies. One prerequisite for advancing personalized medicine is modeling the immune system of individuals or disease groups in a preclinical setting. HIS mice engrafted with peripheral blood mononuclear cells have provided fundamental insights in underlying mechanisms guiding immune activation vs. regulation in several diseases including cancer. However, the development of Graft-vs.-host disease restrains relevant long-term studies in HIS mice. Alternatively, engraftment with hematopoietic stem cells (HSCs) enables mimicking different disease stages, however, low frequencies of HSCs in peripheral blood of adults impede engraftment efficacy. One possibility to overcome those limitations is the use of patient-derived induced pluripotent stem cells (iPSCs) reprogrammed into HSCs, a challenging process which has recently seen major advances. Personalized HIS mice bridge research in mice and human diseases thereby facilitating the translation of immunomodulatory therapies. Regulatory T cells (Tregs) are important mediators of immune suppression and thereby contribute to tumor immune evasion, which has made them a central target for cancer immunotherapies. Importantly, studying Tregs in the human immune system in vivo in HIS mice will help to determine requirements for efficient Treg-targeting. In this review article, we discuss advances on personalized HIS models using reprogrammed iPSCs and review the use of HIS mice to study requirements for efficient targeting of human Tregs for personalized cancer immunotherapies.

Muscle nonshivering thermogenesis in a feral mammal.

Muscle nonshivering thermogenesis (NST) was recently suggested to play an important role in thermoregulation of species lacking brown adipose tissue (BAT). The mechanism, which is independent of muscle contractions, produces heat based on the activity of an ATPase pump in the sarcoplasmic reticulum (SERCA1a) and is controlled by the protein sarcolipin. To evaluate whether muscle NST could indeed play an important role in thermoregulation in species lacking BAT, we investigated the thermogenic capacities of newborn wild boar piglets. During cold exposure over the first 5 days of life, total heat production was improved while shivering intensity decreased, indicating an increasing contribution of NST. Sampling skeletal muscle tissue for analyses of SERCA activity as well as gene expression of SERCA1a and sarcolipin, we found an age-related increase in all three variables as well as in body temperature. Hence, the improved thermogenesis during the development of wild boars is not due to shivering but explained by the observed increase in SERCA activity. Our results suggest that muscle NST may be the primary mechanism of heat production during cold stress in large mammals lacking BAT, strengthening the hypothesis that muscle NST has likely played an important role in the evolution of endothermy.

Covalent dimerization of interleukin-like epithelial-to-mesenchymal transition (EMT) inducer (ILEI) facilitates EMT, invasion, and late aspects of metastasis.

The interleukin-like epithelial-to-mesenchymal transition (EMT) inducer (ILEI)/FAM3C is a member of the highly homologous FAM3 family and is essential for EMT and metastasis formation. It is upregulated in several cancers, and its altered subcellular localization strongly correlates with poor survival. However, the mechanism of ILEI action, including the structural requirements for ILEI activity, remains elusive. Here, we show that ILEI formed both monomers and covalent dimers in cancer cell lines and in tumors. Using mutational analysis and pulse-chase experiments, we found that the four ILEI cysteines, conserved throughout the FAM3 family and involved in disulfide bond formation were essential for extracellular ILEI accumulation in cultured cells. Modification of a fifth cysteine (C185), unique for ILEI, did not alter protein secretion, but completely inhibited ILEI dimerization. Wild-type ILEI monomers, but not C185A mutants, could be converted into covalent dimers extracellularly upon overexpression by intramolecular-to-intermolecular disulfide bond isomerization. Incubation of purified ILEI with cell culture medium showed that dimerization was triggered by bovine serum in a dose- and time-dependent manner. Purified ILEI dimers induced EMT and trans-well invasion of cancer cells in vitro. In contrast, ILEI monomers and the dimerization-defective C185A mutant affected only cell motility as detected by scratch assays and cell tracking via time-lapse microscopy. Importantly, tumor cells overexpressing wild-type ILEI caused large tumors and lung metastases in nude mice, while cells overexpressing the dimerization-defective C185A mutant behaved similar to control cells. These data show that covalent ILEI self-assembly is essential for EMT induction, elevated tumor growth, and metastasis.