Nonspecific "lymphocyte activating" factors produced by macrophages.
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BACKGROUND: Well-differentiated systemic mastocytosis (WDSM) is a rare myeloid neoplasm where the genetic etiology is often unknown. OBJECTIVE: We aimed to assess WDSM patients for novel KIT variants, mast cell (MC) aberrant immunophenotypes, and KIT autophosphorylation patterns. METHODS: Next-generation sequencing, MC immunophenotyping, and KIT autophosphorylation studies were performed. RESULTS: Among 454 SM patients, there were 432 with KIT p.D816V+ SM and 4 with KIT p.D816Y+ SM-notably, none of these patients had WDSM. Of the remaining patients, we identified 7 with WDSM (1.5%) and 2 relatives with mastocytosis in skin. Next-generation sequencing revealed that 6 of 9 subjects carried known or novel germline KIT variants corresponding to regions outside of codon 816. Three patients had germline KIT p.K509I; 2 had germline KIT p.A533D; 1 had two germline KIT variants p.F681L and p.M541L; and 3 had no KIT mutation. Intracellular expression of CD2 and CD25 and less robust expression of CD30 was observed in MCs from WDSM patients. By developing a novel transient transfection assay in 293T cells, we found that unlike KIT p.D816F/V/Y variants that exhibit nearly exclusive intracellular localization and strong ligand-independent autophosphorylation (class II), WDSM-associated KIT variants showed enhanced ligand-dependent autophosphorylation relative to wild type (class I). CONCLUSIONS: Our study doubles the number of KIT variants identified in WDSM patients. No KIT p.D816V+ SM patient had WDSM. Intracellular CD2 and CD25 expression was more robustly detected in MCs from WDSM patients compared to CD30.
Follicular helper T cells (TFH cells) are CD4(+) T cells specialized in helping B cells and are associated both with protective antibody responses and autoimmune diseases. The promise of targeting TFH cells therapeutically has been limited by fragmentary understanding of extrinsic signals that regulate the differentiation of human TFH cells. A screen of a human protein library identified activin A as a potent regulator of TFH cell differentiation. Activin A orchestrated the expression of multiple genes associated with the TFH program, independently or in concert with additional signals. TFH cell programming by activin A was antagonized by the cytokine IL-2. Activin A's ability to drive TFH cell differentiation in vitro was conserved in non-human primates but not in mice. Finally, activin-A-induced TFH programming was dependent on signaling via SMAD2 and SMAD3 and was blocked by pharmacological inhibitors.
T follicular helper (Tfh) cells and T follicular regulatory (Tfr) cells play critical roles in regulating the activity of the germinal center (GC), which is essential for the generation of high-affinity antibodies. In the GC, Tfh cells help B cells to proliferate and to differentiate into memory B cells and long-lived plasma cells. In contrast, Tfr cells, a specialized subset of regulatory T cells (Tregs), modulate the humoral immune response by suppressing excessive or autoreactive B-cell activity. Here, we established an in vitro differentiation protocol for mouse CD4⁺ T cells that yielded CXCR5⁺FoxP3⁺ Tfr cells that exhibited a Bcl6hiPD-1hiCD25loGITRint phenotype and were distinct from Treg and Tfh cells. Functionally, in vitro-generated Tfr cells potently suppressed Tfh cell-driven B-cell class switching to IgG1 and downregulated the expression of B-cell costimulatory ligands. While in vitro-generated Bcl6-deficient Tfh cells were impaired in providing help to B cells for efficient class switching to IgG1, in vitro-generated Bcl6-deficient Tfr cells failed to inhibit Tfh cell-driven B-cell class switching to IgG1. Mechanistically, we showed that Tfr cells emerged from FoxP3+ precursors in low-IL-2 environments through a TGF-β- and c-Maf-dependent pathway, allowing for reprogramming and reinforcement of the follicular regulatory cell program in CD4+ T cells in vitro.
Rabbit bone-marrow macrophages and fibroblasts were cultured, independently or together, with pieces of 35S-labelled cartilage or at the surface of dried [14C]collagen gels. Each type of cell, cultivated alone, rapidly degraded the proteoglycan of cartilage, but only the fibroblasts degraded collagen. The co-culture of both types of cell had no consistent effect on the rate of proteoglycan degradation, but it stimulated the rate of collagen degradation. In parallel, the accumulation of collagenase in the culture fluid was enhanced but not that of neutral proteinase. Coinditioned media from macrophage cultures added to cultures of fibroblasts had the same effect as the living macrophages in stimulating the production of collagenase. Their action was itself enhanced when the macrophages had been activated by concanavalin A-stimulated spleen-cell factors. These data suggest that fibroblasts may act as effector cells in producing collagenase and degrading collagen in response to soluble factors released by macrophages under the control of lymphocyte factors.
Acquisition of effector properties is a key step in the generation of cytotoxic T lymphocytes (CTLs). Here we show that inflammatory signals regulate Dicer expression in CTLs, and that deletion or depletion of Dicer in mouse or human activated CD8(+) T cells causes up-regulation of perforin, granzymes, and effector cytokines. Genome-wide analysis of microRNA (miR, miRNA) changes induced by exposure of differentiating CTLs to IL-2 and inflammatory signals identifies miR-139 and miR-150 as components of an miRNA network that controls perforin, eomesodermin, and IL-2Rα expression in differentiating CTLs and whose activity is modulated by IL-2, inflammation, and antigenic stimulation. Overall, our data show that strong IL-2R and inflammatory signals act through Dicer and miRNAs to control the cytolytic program and other aspects of effector CTL differentiation.
Class II histone deacetylases (HDACs) are important in regulation of gene transcription during T cell development. However, our understanding of their cell-specific functions is limited. In this study, we reveal that class IIa Hdac4 and Hdac7 (Hdac4/7) are selectively induced in transcription, guiding the lineage-specific differentiation of mouse T-helper 17 (Th17) cells from naive CD4+ T cells. Importantly, Hdac4/7 are functionally dispensable in other Th subtypes. Mechanistically, Hdac4 interacts with the transcription factor (TF) JunB, facilitating the transcriptional activation of Th17 signature genes such as Il17a/f. Conversely, Hdac7 collaborates with the TF Aiolos and Smrt/Ncor1-Hdac3 corepressors to repress transcription of Th17 negative regulators, including Il2, in Th17 cell differentiation. Inhibiting Hdac4/7 through pharmacological or genetic methods effectively mitigates Th17 cell-mediated intestinal inflammation in a colitis mouse model. Our study uncovers molecular mechanisms where HDAC4 and HDAC7 function distinctively yet cooperatively in regulating ordered gene transcription during Th17 cell differentiation. These findings suggest a potential therapeutic strategy of targeting HDAC4/7 for treating Th17-related inflammatory diseases, such as ulcerative colitis.
A procedure using preparative free-flow high voltage electrophoresis is described for the fractionation of murine spleen and bone marrow cells so as to obtain cell subpopulations that are either enriched in or depleted of "natural killer" (NK) cells and "mitogen-induced cellular cytotoxicity" (MICC) effector cells. A nearly three fold enrichment in the NK and MICC activities of spleen cells was achieved. The enrichment in these cells could be further increased if the phagocytic cells were removed prior to electrophoresis. When bone marrow cells were fractionated a two and a half fold increase of NK activity, and a one and a half fold enrichment of MICC activity was achieved. In both cases, other fractions were nearly devoid of NK and MICC activity. The cell recovery after electrophoresis averages 70% of the cells applied, and at least 90% of these cells were viable. MICC and NK effector cells could not be separated to a useful extent electrophoretically but were found to be separable using Sephadex C-10 gel filtration columns. The MICC but not the NK cells were retained on these columns.
Emerging evidence links reactive oxygen species modulator 1 (ROMO1), a key mitochondrial ROS regulator, to rheumatoid arthritis (RA) pathogenesis. However, its exact mechanism remains elusive given the conflicting evidence about its specific function. We used a four-level integrative framework combining multi-omics data and literature‑supported mechanistic inference. At the genetic level, Mendelian randomization (MR) was performed to explore potential causal relationships between ROMO1, IL2RA, HLA-DR, MIF, and RA risk, followed by differential expression analysis and machine learning-based feature selection to identify key mROS genes. The temporal expression dynamics of ROMO1 were assessed in RA progression. At the cellular and tissue levels, we integrated single-cell RNA sequencing and spatial transcriptomics to map cell-type-specific expression and synovial localization of ROMO1-related immune cells and pathways. Finally, our multi-omics findings were contextualized with literature-supported mechanistic inference. (1) MR results were consistent with a potential protective effect of ROMO1 on RA (OR = 0.52) and its potential regulation of risk factors IL2RA (OR = 0.46) and HLA-DR (OR = 0.40). Conversely, IL2RA (OR = 1.42), HLA-DR (OR = 1.88), and MIF (OR = 1.17) were positively associated with RA risk. Additionally, ROMO1 was identified as a top candidate diagnostic predictor with stage-specific dynamics: downregulated in the early but upregulated in the late/remission stages. (2) Single-cell RNA sequencing showed ROMO1's cell-specific expression in CD14+ HLA-DR+ CD74+ monocytes and CD4+ IL2RA+ T cells. Cell communication analysis further suggested that these cells may participate in MIF pathway regulation. Spatial transcriptomics subsequently identified that ROMO1-related cells localized to synovial pathological regions, with MIF pathway changes correlated with RA progression. (3) Finally, literature-supported mechanistic inference suggests that ROMO1 may modulate mROS levels to promote anti-inflammatory M2 macrophage polarization, which could theoretically contribute to reduced systemic inflammation and the alleviation of multi-organ decline in RA. This integrated multi-omics investigation, supported by literature-based mechanistic inference, suggests ROMO1 as a stage-dependent biomarker candidate and potential immune regulator in RA.
The nature of the helper lymphocytes in lymphocytosis-promoting factor (LPF)-induced proliferation was explored. Removal of macrophages from adherent splenocytes by either carbonyl-iron incubation or passage through Sephadex G-10 columns did not affect their synergistic function. Nor did cytolysis with Thy-1.2 antiserum and complement. The helper cells were found to be surface immunoglobulin-positive (sIg+) because they are retained by anti-Ig columns, susceptible to lysis by rabbit anti-mouse immunoglobulin and complement, and occurred in the sIg+ fractions of splenocytes after separation on the fluorescence-activated cell sorter. Further delineation of the surface markers on helper cells showed that complement receptors are not the determining marker for synergistic function. The requirement for B-helper cells in the stimulation of T lymphocytes by LPF is unique for a mouse of T-cell mitogen.
This study aimed to elucidate the potential correlation between gut microbiota and intrahepatic cholangiocarcinoma (ICC) by investigating their causal relationship, while also exploring the possible role of immune cells as mediators in this association. We first identified gut microbiota based on phylum, class, order, family, and genus level information. Using summary-level data from a Genome-Wide Association Study (GWAS), we performed a 2-sample Mendelian randomization (MR) analysis of ICC and gut microbiota. Furthermore, we used 2-step MR to quantify the proportion of the effect of immune cell-mediated gut microbiota on ICC. MR analysis identified pyruvate fermentation to acetone (PFA) as predicting ICC risk reduction. There was no strong evidence that genetically predicted ICC had an effect on PFA risk. Furthermore, the proportion of genetically predicted PFA mediated by CD25hi CD45RA+ CD4 not Treg %T cell (CCCTT) was 3% (95% CI: 0.93-5.03%). In conclusion, our study established a causal relationship between PFA and ICC. We observed that a minor fraction of this effect was mediated by CCCTT, while the majority of the impact exerted by PFA on ICC remains elusive. However, further investigations are warranted to elucidate the mechanisms underlying the influence of gut microbiota on ICC development.
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Macrophages may exert a regulatory influence at various stages in the life of the lymphocyte - they may influence the non-antigen-driven differentiation of lymphocytes - as exemplified by the effects on thymic differentiation; they may establish the mode and form of antigen to be presented or recognized by the lymphocyte; may regulate the lymphocyte's antigen-driven functions. Each of these critical regulatory steps needs explaining in molecular terms and integrated and placed in the context of the other regulatory functions of lymphocytes. The control of secretion of MP is an eloquent example of the molecular complexities and the intricate congrol mechanisms - internal and external - operating at each step of each regulatory process. A final comment concern the question of macrophage heterogeneity. Is the same cell performing all the functions of degradation, presentation, and secretion - or cytotoxicity? Or do we have subpopulation, each with a different role? This issue is not settled. The unitarians argue that the phagocytes pass through different stages of differentiation and that each function may become more or less prominent at each stage. Certainly, the manner in which each macrophage function is assayed can condition the outcome: for antigen presentation, one adds 1 % of macrophages to cultures of spleen cells; for cytotoxic assays, the figure is 50 to 100 macrophages per tumor cell! It is our feeling that until such time as membrane molecules are identified and used as probes for differentiation or for identification of subsets we will not resolve this issue. Along these lines, macrophages have been found to have Ia antigens (Hämmerling et al. 1975, Schwartz et al. 1976) and can be divided into two sets on the basis of the presence or absence of Ia. Dorf and I have found - by cytotoxicity - that only about 35 to 50% of peritoneal macrophages bear Ia molecules (Dorf & Uanue 1977). Exceptionally, some exudates will bear up to 75% positive cells. Neither Ia-positive nor Ia-negative macrophages change significantly after prolonged periods of culture. Whether these results indicate two defined subsets of macrophages is now being investigated.
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Human monocytes have been reported to release factors that can elicit distinct responses from a number of different target cells. In this report, it is shown that most of the thymocyte-stimulating activity in supernatants of endotoxin-stimulated monocytes can be separated from the plaque-stimulating factor (BAF) by gel filtration and isoelectric focusing; however, since these activities could not be entirely resolved, the question was addressed whether the plaque-stimulating activity of BAF depends upon the stimulation of T-cells. Several critical experiments are reported which fail to support this hypothesis. On the other hand, these experiments led to the observation that the response to BAF depends on both an IgM-positive B-cell and a G10-adherent, plastic nonadherent, IgM-negative, irradiation-insensitive cell found in nude splenocytes. Finally, the possibility is discussed that this factor may be responsible for many of the physiological sequelae of infection.