In Vivo Labeling Resolves Distinct Temporal, Spatial, and Functional Properties of Tumor Macrophages and Identifies Subset-Specific Effects of PD-L1 Blockade.

Tumor-associated macrophages (TAM) are a universal feature of cancers but variably influence outcomes and treatment responses. In this study, we used a photoconvertible mouse to distinguish newly entering, monocyte-derived TAMs (mdTAM) that were enriched at the tumor core from resident-like TAMs that localized with fibroblasts at the tumor-normal interface. The mdTAM pool was highly dynamic and continually replenished by circulating monocytes.

Advancing Cellular-Specific Delivery: Machine Learning Insights into Lipid Nanoparticles Design and Cellular Tropism.

Lipid nanoparticles (LNPs) have gained significant attention as effective nucleic acid delivery vehicles. Despite their success, LNPs are predominantly liver-targeted which limits their broader application. To expand the therapeutic potential of LNPs, this work implements a data-driven approach that combines design of experiments (DoE), high throughput screening (HTS), and machine learning (ML) to tailor LNP formulations for preferential immune cell targeting.

Tumour-retained activated CCR7 dendritic cells are heterogeneous and regulate local anti-tumour cytolytic activity.

Tumour dendritic cells (DCs) internalise antigen and upregulate CCR7, which directs their migration to tumour-draining lymph nodes (dLN). CCR7 expression is coupled to an activation programme enriched in regulatory molecule expression, including PD-L1. However, the spatio-temporal dynamics of CCR7 DCs in anti-tumour immune responses remain unclear.

Rapid functional impairment of natural killer cells following tumor entry limits anti-tumor immunity.

Immune cell dysfunction within the tumor microenvironment (TME) undermines the control of cancer progression. Established tumors contain phenotypically distinct, tumor-specific natural killer (NK) cells; however, the temporal dynamics, mechanistic underpinning and functional significance of the NK cell compartment remains incompletely understood. Here, we use photo-labeling, combined with longitudinal transcriptomic and cellular analyses, to interrogate the fate of intratumoral NK cells.

Targeting the Inducible T-cell Costimulator (ICOS) in Patients with Relapsed/Refractory T-follicular Helper Phenotype Peripheral T-cell and Angioimmunoblastic T-cell Lymphoma.

Purpose: Proliferation of T-follicular helper (TFH) CD4+ T cells is a postulated pathogenic mechanism for T-cell non-Hodgkin lymphomas (T-NHL). The inducible T-cell costimulator (ICOS) is highly expressed by TFH, representing a potential target. MEDI-570 is a monoclonal antibody against ICOS, which eliminates ICOS+ cells in preclinical models.

In vivo labeling reveals continuous trafficking of TCF-1+ T cells between tumor and lymphoid tissue.

Improving the efficacy of immune checkpoint therapies will require a better understanding of how immune cells are recruited and sustained in tumors. Here, we used the photoconversion of the tumor immune cell compartment to identify newly entering lymphocytes, determine how they change over time, and investigate their egress from the tumor. Combining single-cell transcriptomics and flow cytometry, we found that while a diverse mix of CD8 T cell subsets enter the tumor, all CD8 T cells retained within this environment for more than 72 h developed an exhausted phenotype, revealing the rapid establishment of this program.

Immunomodulation of T- and NK-cell Responses by a Bispecific Antibody Targeting CD28 Homolog and PD-L1.

Checkpoint blockade therapies targeting PD-1/PD-L1 and CTLA-4 are clinically successful but also evoke adverse events due to systemic T-cell activation. We engineered a bispecific, mAb targeting CD28 homolog (CD28H), a newly identified B7 family receptor that is constitutively expressed on T and natural killer (NK) cells, with a PD-L1 antibody to potentiate tumor-specific immune responses. The bispecific antibody led to T-cell costimulation, induced NK-cell cytotoxicity of PD-L1-expressing tumor cells, and activated tissue-resident memory CD8 T cells.

Impaired B Cell Apoptosis Results in Autoimmunity That Is Alleviated by Ablation of Btk.

While apoptosis plays a role in B-cell self-tolerance, its significance in preventing autoimmunity remains unclear. Here, we report that dysregulated B cell apoptosis leads to delayed onset autoimmune phenotype in mice. Our longitudinal studies revealed that mice with B cell-specific deletion of pro-apoptotic Bim ( ) have an expanded B cell compartment with a notable increase in transitional, antibody secreting and recently described double negative (DN) B cells.

Unique expansion of IL-21+ Tfh and Tph cells under control of ICOS identifies Sjögren's syndrome with ectopic germinal centres and MALT lymphoma.

Objectives: To explore the relevance of T-follicular-helper (Tfh) and pathogenic peripheral-helper T-cells (Tph) in promoting ectopic lymphoid structures (ELS) and B-cell mucosa-associated lymphoid tissue (MALT) lymphomas (MALT-L) in Sjögren's syndrome (SS) patients.

Methods: Salivary gland (SG) biopsies with matched peripheral blood were collected from four centres across the European Union. Transcriptomic (microarray and quantitative PCR) analysis, FACS T-cell immunophenotyping with intracellular cytokine detection, multicolor immune-fluorescence microscopy and hybridisation were performed to characterise lesional and circulating Tfh and Tph-cells.

Targeting co-stimulatory molecules in autoimmune disease.

Therapeutic targeting of immune checkpoints has garnered significant attention in the area of cancer immunotherapy, in which efforts have focused in particular on cytotoxic T lymphocyte antigen 4 (CTLA4) and PD1, both of which are members of the CD28 family. In autoimmunity, these same pathways can be targeted to opposite effect: to curb the over-exuberant immune response. The CTLA4 checkpoint serves as an exemplar, whereby CTLA4 activity is blocked by antibodies in cancer immunotherapy and augmented by the provision of soluble CTLA4 in autoimmunity.

Peripheral lymph nodes contain migratory and resident innate lymphoid cell populations.

Tissue residency is considered a defining feature of the innate lymphoid cell (ILC) populations located within mucosal and adipose tissues. ILCs are also present within all lymphoid tissues, but whether ILCs migrate between lymphoid and nonlymphoid sites and in what context is poorly understood. To determine whether migratory ILCs exist within peripheral lymph nodes (LNs), we labeled all cells within the brachial LN (bLN) of transgenic mice expressing a photoconvertible fluorescent protein by direct exposure to light.

Characterisation of innate lymphoid cell populations at different sites in mice with defective T cell immunity.

: Innate lymphoid cells (ILCs) have now been identified within most tissues of the body and current evidence indicates that this family of cells play a fundamental role in maintaining tissue homeostasis. However, few studies have compared the ILC populations between several tissues. : We sought to generate a comprehensive characterisation of the ILC populations in different tissues of C57BL/6 WT and genetically modified mice targeting costimulatory pathways, using transcription factor expression to define specific groups.

T follicular helper-like cells contribute to skin fibrosis.

Systemic sclerosis (SSc) is a debilitating inflammatory and fibrotic disease that affects the skin and internal organs. Although the pathophysiology of SSc remains poorly characterized, mononuclear cells, mainly macrophages and T cells, have been implicated in inflammation and fibrosis. Inducible costimulator (ICOS), which is expressed on a subset of memory T helper (T) and T follicular helper (T) cells, has been shown to be increased in SSc and associated with disease pathology.

Effects of ICOS+ T cell depletion via afucosylated monoclonal antibody MEDI-570 on pregnant cynomolgus monkeys and the developing offspring.

MEDI-570 is a fully human afucosylated monoclonal antibody (MAb) against Inducible T-cell costimulator (ICOS), highly expressed on CD4+ T follicular helper (T) cells. Effects of MEDI-570 were evaluated in an enhanced pre-postnatal development toxicity (ePPND) study in cynomolgus monkeys. Administration to pregnant monkeys did not cause any abortifacient effects.

Follicular Dendritic Cell Activation by TLR Ligands Promotes Autoreactive B Cell Responses.

A hallmark of autoimmunity in murine models of lupus is the formation of germinal centers (GCs) in lymphoid tissues where self-reactive B cells expand and differentiate. In the host response to foreign antigens, follicular dendritic cells (FDCs) maintain GCs through the uptake and cycling of complement-opsonized immune complexes. Here, we examined whether FDCs retain self-antigens and the impact of this process in autoantibody secretion in lupus.

Cytomegalovirus-Specific IL-10-Producing CD4+ T Cells Are Governed by Type-I IFN-Induced IL-27 and Promote Virus Persistence.

CD4+ T cells support host defence against herpesviruses and other viral pathogens. We identified that CD4+ T cells from systemic and mucosal tissues of hosts infected with the β-herpesviridae human cytomegalovirus (HCMV) or murine cytomegalovirus (MCMV) express the regulatory cytokine interleukin (IL)-10. IL-10+CD4+ T cells co-expressed TH1-associated transcription factors and chemokine receptors.

Loss of Immune Tolerance Is Controlled by ICOS in Sle1 Mice.

ICOS, a member of the CD28 family, represents a key molecule that regulates adaptive responses to foreign Ags. ICOS is prominently expressed on T follicular helper (TFH) cells, a specialized CD4(+) T cell subset that orchestrates B cell differentiation within the germinal centers and humoral response. However, the contribution of ICOS and TFH cells to autoantibody profiles under pathological conditions has not been thoroughly investigated.

ICOS is required for the generation of both central and effector CD4(+) memory T-cell populations following acute bacterial infection.

Interactions between ICOS and ICOS ligand (ICOSL) are essential for the development of T follicular helper (Tfh) cells and thus the formation and maintenance of GC reactions. Given the conflicting reports on the requirement of other CD4(+) T-cell populations for ICOS signals, we have employed a range of in vivo approaches to dissect requirements for ICOS signals in mice during an endogenous CD4(+) T-cell response and contrasted this with CD28 signals. Genetic absence of ICOSL only modestly reduced the total number of antigen-specific CD4(+) T cells at the peak of the primary response, but resulted in a severely diminished number of both T central memory and T effector memory cells.

Germinal center B cell depletion diminishes CD4+ follicular T helper cells in autoimmune mice.

Background: Continuous support from follicular CD4(+) T helper (Tfh) cells drives germinal center (GC) responses, which last for several weeks to produce high affinity memory B cells and plasma cells. In autoimmune Sle1 and NZB/W F1 mice, elevated numbers of Tfh cells persist, promoting the expansion of self-reactive B cells. Expansion of circulating Tfh like cells have also been described in several autoimmune diseases.

Cell distance mapping identifies functional T follicular helper cells in inflamed human renal tissue.

T follicular helper (TFH) cells are critical for B cell activation in germinal centers and are often observed in human inflamed tissue. However, it is difficult to know if they contribute in situ to inflammation. Expressed markers define TFH subsets associated with distinct functions in vitro.

Absence of mature peripheral B cell populations in mice with concomitant defects in B cell receptor and BAFF-R signaling.

Generation of mature B lymphocytes from early (T1) and late transitional (T2) precursors requires cooperative signaling through BCR and B cell-activating factor receptor 3 (BR3). Recent studies have shown that BCR signaling positively regulates NF-kappaB2, suggesting BCR regulation of BR3 signaling. To investigate the significance of signal integration from BCR and BR3 in B cell development and function, we crossed Btk-deficient mice (btk(-/-)), which are developmentally blocked between the T2 and the mature follicular B cell stage as a result of a partial defect in BCR signaling, and A/WySnJ mice, which possess a mutant BR3 defective in propagating intracellular signals that results in a severely reduced peripheral B cell compartment, although all B cell subsets are present in relatively normal ratios.

B cell receptor-mediated sustained c-Rel activation facilitates late transitional B cell survival through control of B cell activating factor receptor and NF-kappaB2.

Signaling from the BCR and B cell activating factor receptor (BAFF-R or BR3) differentially regulates apoptosis within early transitional (T1) and late transitional (T2; CD21(int)-T2) B cells during selection processes to generate mature B lymphocytes. However, molecular mechanisms underlying the differential sensitivity of transitional B cells to apoptosis remain unclear. In this study, we demonstrate that BCR signaling induced more long-term c-Rel activation in T2 and mature than in T1 B cells leading to increased expression of anti-apoptotic genes as well as prosurvival BAFF-R and its downstream substrate p100 (NF-kappaB2).