Type 2 innate lymphoid cells (ILC2s) are crucial in regulating immune responses and various physiological processes, including tissue repair, metabolic homeostasis, inflammation, and cancer surveillance. Here, we present a protocol that outlines the isolation, expansion, and adoptive transfer of human ILC2s from peripheral blood mononuclear cells for an in vivo lineage tracking experiment in a mouse model. Additionally, we detail the steps involved in the adoptive transfer of human ILC2s to recipient mice bearing human liquid or solid tumors. For complete details on the use and execution of this protocol, please refer to Li et al.1.
Copyright © 2024. Published by Elsevier Inc.

RAS pathway mutations, which are present in 30% of patients with chronic myelomonocytic leukemia (CMML) at diagnosis, confer a high risk of resistance to and progression after hypomethylating agent (HMA) therapy, the current standard of care for the disease. Here, using single-cell, multi-omics technologies, we seek to dissect the biological mechanisms underlying the initiation and progression of RAS pathway-mutated CMML. We identify that RAS pathway mutations induce transcriptional reprogramming of hematopoietic stem and progenitor cells (HSPCs) and downstream monocytic populations in response to cell-intrinsic and -extrinsic inflammatory signaling that also impair the functions of immune cells. HSPCs expand at disease progression after therapy with HMA or the BCL2 inhibitor venetoclax and rely on the NF-κB pathway effector MCL1 to maintain survival. Our study has implications for the development of therapies to improve the survival of patients with RAS pathway-mutated CMML.
Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.

The therapeutic potential for human type 2 innate lymphoid cells (ILC2s) has been underexplored. Although not observed in mouse ILC2s, we found that human ILC2s secrete granzyme B (GZMB) and directly lyse tumor cells by inducing pyroptosis and/or apoptosis, which is governed by a DNAM-1-CD112/CD155 interaction that inactivates the negative regulator FOXO1. Over time, the high surface density expression of CD155 in acute myeloid leukemia cells impairs the expression of DNAM-1 and GZMB, thus allowing for immune evasion. We describe a reliable platform capable of up to 2,000-fold expansion of human ILC2s within 4 weeks, whose molecular and cellular ILC2 profiles were validated by single-cell RNA sequencing. In both leukemia and solid tumor models, exogenously administered expanded human ILC2s show significant antitumor effects in vivo. Collectively, we demonstrate previously unreported properties of human ILC2s and identify this innate immune cell subset as a member of the cytolytic immune effector cell family.
Copyright © 2023 Elsevier Inc. All rights reserved.

Although gut and lymph node (LN) memory CD4 T cells represent major HIV and simian immunodeficiency virus (SIV) tissue reservoirs, the study of the role of dendritic cells (DCs) in HIV persistence has long been limited to the blood due to difficulties to access lymphoid tissue samples. In this study, we show that LN migratory and resident DC subpopulations harbor distinct phenotypic and transcriptomic profiles. Interestingly, both LN DC subpopulations contain HIV intact provirus and inducible replication-competent HIV despite the expression of the antiviral restriction factor SAMHD1. Notably, LN DC subpopulations isolated from HIV-infected individuals treated for up to 14 years are transcriptionally silent but harbor replication-competent virus that can be induced upon TLR7/8 stimulation. Taken together, these results uncover a potential important contribution of LN DCs to HIV infection in the presence of ART.
Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.

ABSTRACT Bone marrow (BM) involvement is a common feature of lymphomas deriving from germinal-center B cells and is associated with a bad prognosis. In particular, follicular lymphoma (FL) infiltrates the BM in 70% of cases, in association with a remodeling of surrounding tumor microenvironment. Analysis of in vitro -expanded FL mesenchymal stromal cells (MSCs) revealed an extensive alteration of BM stromal cell phenotypic, transcriptomic, and functional profiles. However, the mechanisms supporting the direct interplay between lymphoma B cells and their permissive stromal niche in situ have not been yet identified. In the current work, we identified in the BM milieu of FL patients a deregulation of soluble and extracellular matrix (ECM) components reflecting inflammation and ectopic differentiation into lymphoid-like stromal cells. We reproduced the same alterations in a murine model of lymphoma B-cell xenograft where a scRNAseq approach identified LepR pos MSCs as specifically and progressively reprogramed by tumor B-cell invasion. Analysis of FL BM collected before and after treatment confirmed that BM niche was partly dependent on the continuous contact with tumor B cells. Altogether, this work shed new lights on the kinetic and mechanisms of BM stromal niche reshaping in B-cell lymphoma.