Elastin-derived peptides favor type 2 innate lymphoid cells in chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is a condition characterized by chronic airway inflammation and obstruction, primarily caused by tobacco smoking. Although the involvement of immune cells in COPD pathogenesis is well established, the contribution of innate lymphoid cells (ILCs) remains poorly understood. ILCs are a type of innate immune cells that participate in tissue remodeling processes, but their specific role in COPD has not been fully elucidated. During COPD, the breakdown of pulmonary elastin generates elastin peptides that elicit biological activities on immune cells. This study aimed to investigate the presence of ILC in patients with COPD and examine the impact of elastin peptides on their functionality. Our findings revealed an elevated proportion of ILC2 in the peripheral blood of patients with COPD, and a general activation of ILC as indicated by an increase in their cytokine secretion capacity. Notably, our study demonstrated that serum from patients with COPD promotes ILC2 phenotype, likely due to the elevated concentration of IL-5, a cytokine known to favor ILC2 activation. Furthermore, we uncovered that this increase in IL-5 secretion is partially attributed to its secretion by macrophages upon stimulation by elastin peptides, suggesting an indirect role of elastin peptides on ILC in COPD. These findings shed light on the involvement of ILC in COPD and provide insights into the potential interplay between elastin breakdown, immune cells, and disease progression. Further understanding of the mechanisms underlying ILC activation and their interaction with elastin peptides could contribute to the development of novel therapeutic strategies for COPD management.NEW & NOTEWORTHY Elastin-derived peptides, generated following alveolar degradation during emphysema in patients with COPD, are able to influence the response of type 2 innate lymphoid cells. We show that the orientation of innate lymphoid cells in patients with COPD is shifted toward a type 2 profile and that elastin peptides are indirectly participating in that shift through their influence of macrophages, which in turn impact innate lymphoid cells.

Identification of a new subset of lymph node stromal cells involved in regulating plasma cell homeostasis.

Antibody-secreting plasma cells (PCs) arise rapidly during adaptive immunity to control infections. The early PCs are retained within the reactive lymphoid organ where their localization and homeostasis rely on extrinsic factors, presumably produced by local niche cells. While myeloid cells have been proposed to form those niches, the contribution by colocalizing stromal cells has remained unclear. Here, we characterized a subset of fibroblastic reticular cells (FRCs) that forms a dense meshwork throughout medullary cords of lymph nodes (LNs) where PCs reside. This medullary FRC type is shown to be anatomically, phenotypically, and functionally distinct from T zone FRCs, both in mice and humans. By using static and dynamic imaging approaches, we provide evidence that medullary FRCs are the main cell type in contact with PCs guiding them in their migration. Medullary FRCs also represent a major local source of the PC survival factors IL-6, BAFF, and CXCL12, besides also producing APRIL. In vitro, medullary FRCs alone or in combination with macrophages promote PC survival while other LN cell types do not have this property. Thus, we propose that this FRC subset, together with medullary macrophages, forms PC survival niches within the LN medulla, and thereby helps in promoting the rapid development of humoral immunity, which is critical in limiting early pathogen spread.

TCR signaling events are required for maintaining CD4 regulatory T cell numbers and suppressive capacities in the periphery.

CD4 regulatory T cells (Tregs) can be subdivided into two subsets according to Ly-6C expression in the periphery. Phenotypic analysis, imaging, and adoptive-transfer experiments of peripheral Ly-6C(-) and Ly-6C(+) Tregs reveal that the nonexpression of Ly-6C by ∼70% of peripheral Tregs depends on TCR signaling events. Interestingly, Ly-6C(-) Tregs express higher surface amounts of key immunosuppressive molecules than do Ly-6C(+) Tregs and produce constitutively anti-inflammatory cytokines. In line with their phenotype, Ly-6C(+) Tregs exhibit poor suppressive capacities in vitro and in vivo. Finally, although Ly-6C(-) Tregs maintain their numbers with age, Ly-6C(+) Tregs gradually disappear. Altogether, our data strongly suggest that both the survival and suppressive functions of peripheral CD4 Tregs rely on their ability to receive strong TCR signals.

Inflammatory monocytes are potent antitumor effectors controlled by regulatory CD4+ T cells.

The present study evaluates the impact of immune cell populations on metastatic development in a model of spontaneous melanoma [mice expressing the human RET oncogene under the control of the metallothionein promoter (MT/ret mice)]. In this model, cancer cells disseminate early but remain dormant for several weeks. Then, MT/ret mice develop cutaneous metastases and, finally, distant metastases. A total of 35% of MT/ret mice develop a vitiligo, a skin depigmentation attributable to the lysis of normal melanocytes, associated with a delay in tumor progression. Here, we find that regulatory CD4(+) T cells accumulate in the skin, the spleen, and tumor-draining lymph nodes of MT/ret mice not developing vitiligo. Regulatory T-cell depletion and IL-10 neutralization led to increased occurrence of vitiligo that correlated with a decreased incidence of melanoma metastases. In contrast, inflammatory monocytes/dendritic cells accumulate in the skin of MT/ret mice with active vitiligo. Moreover, they inhibit tumor cell proliferation in vitro through a reactive oxygen species-dependent mechanism, and both their depletion and reactive oxygen species neutralization in vivo increased tumor cell dissemination. Altogether, our data suggest that regulatory CD4(+) T cells favor tumor progression, in part, by inhibiting recruitment and/or differentiation of inflammatory monocytes in the skin.

IL-2 and IL-7 determine the homeostatic balance between the regulatory and conventional CD4+ T cell compartments during peripheral T cell reconstitution.

Work over the last decades has led to the identification of the factors that influence the survival and homeostasis of conventional T cells. IL-7 and TCR signaling promote the survival of naive CD4(+) and CD8(+) T cells in lymphoreplete mice and their proliferation in a lymphopenic environment, whereas survival and homeostatic proliferation of memory CD4(+) and CD8(+) T cells crucially depend on a combination of IL-7 and IL-15. In contrast, there is little information regarding the factors driving the proliferation of regulatory CD4(+) T cells in response to lymphopenia. In this study, we investigated whether regulatory CD4(+) T cell proliferation in response to lymphopenia was guided by classical homeostatic resources, such as IL-2, IL-7, or TCR-MHC interactions. Altogether, our data suggest that, although homeostatic proliferation of conventional naive CD4(+) T cells is closely related to IL-7 levels, the proliferation of regulatory CD4(+) T cells in response to lymphopenia appears to be primarily controlled by IL-2. The capacity of IL-7 to augment conventional T cell proliferation with minimal concomitant regulatory T cell expansion may be clinically exploitable in the treatment of patients with lymphopenia, especially in the case of chronic viral diseases or cancer immunotherapy.

Foxp3-independent loss of regulatory CD4+ T-cell suppressive capacities induced by self-deprivation.

In the periphery, Foxp3 expression is considered sufficient to maintain natural regulatory CD4(+) T-cell suppressive function. In this study, we challenge this model. Indeed, in mouse chimeras in which major histocompatibility complex (MHC) class II expression is restricted to the thymus, peripheral regulatory CD4(+) T cells lack suppressive activity. In addition, regulatory CD4(+) T cells recovered 5 days after transfer into recipient mice lacking expression of MHC class II molecules (self-deprived) are unable to inhibit the proliferative response of conventional CD4(+) T cells both in vitro and in vivo. Disruption of TCR/MHC class II interactions rapidly leads to alterations in the regulatory CD4(+) T-cell phenotype, the ability to respond to stimulation and to produce interleukin-10, and the transcriptional signature. Interestingly, self-deprivation does not affect Foxp3 expression indicating that in regulatory CD4(+) T cells, self-recognition induces unique transcriptional and functional features that do not rely on Foxp3 expression.

Cancer cell CCR2 orchestrates suppression of the adaptive immune response.

C-C chemokine receptor type 2 (CCR2) is expressed on monocytes and facilitates their recruitment to tumors. Though breast cancer cells also express CCR2, its functions in these cells are unclear. We found that Ccr2 deletion in cancer cells led to reduced tumor growth and approximately twofold longer survival in an orthotopic, isograft breast cancer mouse model. Deletion of Ccr2 in cancer cells resulted in multiple alterations associated with better immune control: increased infiltration and activation of cytotoxic T lymphocytes (CTLs) and CD103+ cross-presenting dendritic cells (DCs), as well as up-regulation of MHC class I and down-regulation of checkpoint regulator PD-L1 on the cancer cells. Pharmacological or genetic targeting of CCR2 increased cancer cell sensitivity to CTLs and enabled the cancer cells to induce DC maturation toward the CD103+ subtype. Consistently, Ccr2-/- cancer cells did not induce immune suppression in Batf3-/- mice lacking CD103+ DCs. Our results establish that CCR2 signaling in cancer cells can orchestrate suppression of the immune response.

The glycan CA19-9 promotes pancreatitis and pancreatic cancer in mice.

Glycosylation alterations are indicative of tissue inflammation and neoplasia, but whether these alterations contribute to disease pathogenesis is largely unknown. To study the role of glycan changes in pancreatic disease, we inducibly expressed human fucosyltransferase 3 and ß1,3-galactosyltransferase 5 in mice, reconstituting the glycan sialyl-Lewisa, also known as carbohydrate antigen 19-9 (CA19-9). Notably, CA19-9 expression in mice resulted in rapid and severe pancreatitis with hyperactivation of epidermal growth factor receptor (EGFR) signaling. Mechanistically, CA19-9 modification of the matricellular protein fibulin-3 increased its interaction with EGFR, and blockade of fibulin-3, EGFR ligands, or CA19-9 prevented EGFR hyperactivation in organoids. CA19-9-mediated pancreatitis was reversible and could be suppressed with CA19-9 antibodies. CA19-9 also cooperated with the KrasG12D oncogene to produce aggressive pancreatic cancer. These findings implicate CA19-9 in the etiology of pancreatitis and pancreatic cancer and nominate CA19-9 as a therapeutic target.

Unresolved endoplasmic reticulum stress engenders immune-resistant, latent pancreatic cancer metastases.

The majority of patients with pancreatic ductal adenocarcinoma (PDA) develop metastatic disease after resection of their primary tumor. We found that livers from patients and mice with PDA harbor single disseminated cancer cells (DCCs) lacking expression of cytokeratin 19 (CK19) and major histocompatibility complex class I (MHCI). We created a mouse model to determine how these DCCs develop. Intraportal injection of immunogenic PDA cells into preimmunized mice seeded livers only with single, nonreplicating DCCs that were CK19- and MHCI- The DCCs exhibited an endoplasmic reticulum (ER) stress response but paradoxically lacked both inositol-requiring enzyme 1α activation and expression of the spliced form of transcription factor XBP1 (XBP1s). Inducible expression of XBP1s in DCCs, in combination with T cell depletion, stimulated the outgrowth of macrometastatic lesions that expressed CK19 and MHCI. Thus, unresolved ER stress enables DCCs to escape immunity and establish latent metastases.

Neutrophil extracellular traps produced during inflammation awaken dormant cancer cells in mice.

Cancer cells from a primary tumor can disseminate to other tissues, remaining dormant and clinically undetectable for many years. Little is known about the cues that cause these dormant cells to awaken, resume proliferating, and develop into metastases. Studying mouse models, we found that sustained lung inflammation caused by tobacco smoke exposure or nasal instillation of lipopolysaccharide converted disseminated, dormant cancer cells to aggressively growing metastases. Sustained inflammation induced the formation of neutrophil extracellular traps (NETs), and these were required for awakening dormant cancer. Mechanistic analysis revealed that two NET-associated proteases, neutrophil elastase and matrix metalloproteinase 9, sequentially cleaved laminin. The proteolytically remodeled laminin induced proliferation of dormant cancer cells by activating integrin α3ß1 signaling. Antibodies against NET-remodeled laminin prevented awakening of dormant cells. Therapies aimed at preventing dormant cell awakening could potentially prolong the survival of cancer patients.

Crucial role of inflammatory monocytes in antitumor immunity.

Although the role of myeloid cells in oncogenesis and tumor progression remains poorly understood, these cells are mainly ascribed with pro-tumor properties. We have recently unveiled a tumoricidal activity of inflammatory monocytes that can be counteracted by CD4+ regulatory T cells.

Highly self-reactive naive CD4 T cells are prone to differentiate into regulatory T cells.

Upon activation, naive CD4 T cells differentiate into a variety of T-helper-cell subsets characterized by different cytokine production and functions. Currently, lineage commitment is considered to depend mostly on the environmental context to which naive CD4 T cells are exposed. Here we challenge this model based on the supposed homogeneity of the naive CD4 T-cell compartment. We show that peripheral naive CD4 T cells can be subdivided into two subsets according to Ly-6C expression. Furthermore, the two newly defined subsets (Ly-6C(-) and Ly-6C(+) naive CD4 T cells) are not equal in their intrinsic ability to commit into the induced regulatory T-cell lineage. Finally, phenotypic analysis, imaging and adoptive transfer experiments reveal that Ly-6C expression is modulated by self-recognition, allowing the dichotomization of the naive CD4 T-cell compartment into two cell subsets with distinct self-reactivity. Altogether, our results show that naive CD4 T cells with the highest avidity for self are prone to differentiate into regulatory T cells.

T cells contribute to tumor progression by favoring pro-tumoral properties of intra-tumoral myeloid cells in a mouse model for spontaneous melanoma.

Tumors affect myelopoeisis and induce the expansion of myeloid cells with immunosuppressive activity. In the MT/ret model of spontaneous metastatic melanoma, myeloid cells are the most abundant tumor infiltrating hematopoietic population and their proportion is highest in the most aggressive cutaneous metastasis. Our data suggest that the tumor microenvironment favors polarization of myeloid cells into type 2 cells characterized by F4/80 expression, a weak capacity to secrete IL-12 and a high production of arginase. Myeloid cells from tumor and spleen of MT/ret mice inhibit T cell proliferation and IFNγ secretion. Interestingly, T cells play a role in type 2 polarization of myeloid cells. Indeed, intra-tumoral myeloid cells from MT/ret mice lacking T cells are not only less suppressive towards T cells than corresponding cells from wild-type MT/ret mice, but they also inhibit more efficiently melanoma cell proliferation. Thus, our data support the existence of a vicious circle, in which T cells may favor cancer development by establishing an environment that is likely to skew myeloid cell immunity toward a tumor promoting response that, in turn, suppresses immune effector cell functions.