Andrew E. Hogan

Tumour Tissue Microenvironment Can Inhibit Dendritic Cell Maturation in Colorectal Cancer

Inflammatory mediators in the tumour microenvironment promote tumour growth, vascular development and enable evasion of anti-tumour immune responses, by disabling infiltrating dendritic cells. However, the constituents of the tumour microenvironment that directly influence dendritic cell maturation and function are not well characterised. Our aim was to identify tumour-associated inflammatory mediators which influence the function of dendritic cells. Tumour conditioned media obtained from cultured colorectal tumour explant tissue contained high levels of the chemokines CCL2, CXCL1, CXCL5 in addition to VEGF. Pre-treatment of monocyte derived dendritic cells with this tumour conditioned media inhibited the up-regulation of CD86, CD83, CD54 and HLA-DR in response to LPS, enhancing IL-10 while reducing IL-12p70 secretion. We examined if specific individual components of the tumour conditioned media (CCL2, CXCL1, CXCL5) could modulate dendritic cell maturation or cytokine secretion in response to LPS. VEGF was also assessed as it has a suppressive effect on dendritic cell maturation. Pre-treatment of immature dendritic cells with VEGF inhibited LPS induced upregulation of CD80 and CD54, while CXCL1 inhibited HLA-DR. Interestingly, treatment of dendritic cells with CCL2, CXCL1, CXCL5 or VEGF significantly suppressed their ability to secrete IL-12p70 in response to LPS. In addition, dendritic cells treated with a combination of CXCL1 and VEGF secreted less IL-12p70 in response to LPS compared to pre-treatment with either cytokine alone. In conclusion, tumour conditioned media strongly influences dendritic cell maturation and function.

Distinct and overlapping effector functions of expanded human CD4+, CD8α+ and CD4-CD8α- invariant natural killer T cells.

CD1d-restricted invariant natural killer T (iNKT) cells have diverse immune stimulatory/regulatory activities through their ability to release cytokines and to kill or transactivate other cells. Activation of iNKT cells can protect against multiple diseases in mice but clinical trials in humans have had limited impact. Clinical studies to date have targeted polyclonal mixtures of iNKT cells and we proposed that their subset compositions will influence therapeutic outcomes. We sorted and expanded iNKT cells from healthy donors and compared the phenotypes, cytotoxic activities and cytokine profiles of the CD4+, CD8α+ and CD4−CD8α− double-negative (DN) subsets. CD4+ iNKT cells expanded more readily than CD8α+ and DN iNKT cells upon mitogen stimulation. CD8α+ and DN iNKT cells most frequently expressed CD56, CD161 and NKG2D and most potently killed CD1d+ cell lines and primary leukemia cells. All iNKT subsets released Th1 (IFN-γ and TNF-α) and Th2 (IL-4, IL-5 and IL-13) cytokines. Relative amounts followed a CD8α>DN>CD4 pattern for Th1 and CD4>DN>CD8α for Th2. All iNKT subsets could simultaneously produce IFN-γ and IL-4, but single-positivity for IFN-γ or IL-4 was strikingly rare in CD4+ and CD8α+ fractions, respectively. Only CD4+ iNKT cells produced IL-9 and IL-10; DN cells released IL-17; and none produced IL-22. All iNKT subsets upregulated CD40L upon glycolipid stimulation and induced IL-10 and IL-12 secretion by dendritic cells. Thus, subset composition of iNKT cells is a major determinant of function. Use of enriched CD8α+, DN or CD4+ iNKT cells may optimally harness the immunoregulatory properties of iNKT cells for treatment of disease.

Cutting Edge: CD1d Restriction and Th1/Th2/Th17 Cytokine Secretion by Human Vδ3 T Cells

Human γδ T cells expressing the Vδ3 TCR make up a minor lymphocyte subset in blood but are enriched in liver and in patients with some chronic viral infections and leukemias. We analyzed the frequencies, phenotypes, restriction elements, and functions of fresh and expanded peripheral blood Vδ3 T cells. Vδ3 T cells accounted for ∼0.2% of circulating T cells, included CD4+, CD8+, and CD4−CD8− subsets, and variably expressed CD56, CD161, HLA-DR, and NKG2D but neither NKG2A nor NKG2C. Vδ3 T cells were sorted and expanded by mitogen stimulation in the presence of IL-2. Expanded Vδ3 T cells recognized CD1d but not CD1a, CD1b, or CD1c. Upon activation, they killed CD1d+ target cells, released Th1, Th2, and Th17 cytokines, and induced maturation of dendritic cells into APCs. Thus, Vδ3 T cells are glycolipid-reactive T cells with distinct Ag specificities but functional similarities to NKT cells.

Preadipocyte Factor-1 Is Associated with Metabolic Profile in Severe Obesity

CONTEXT Dysfunctional adipose tissue has been proposed as a key pathological process linking obesity and metabolic disease. Preadipocyte factor-1 (Pref-1) has been shown to inhibit differentiation in adipocyte precursor cells and could thereby play a role in determining adipocyte size, adipose tissue functioning, and metabolic profile in obese individuals. OBJECTIVE We hypothesized that adipose tissue from metabolically healthy obese (MHO) and matched metabolically unhealthy obese individuals would demonstrate distinct differences in relation to Pref-1 expression, adipocyte size, and inflammatory markers. DESIGN, SETTING, AND PATIENTS This was a cross-sectional study, investigating obese patients undergoing bariatric surgery at a tertiary referral centre. Patients included 12 MHO and 17 age- and body mass index-matched metabolically unhealthy obese individuals. MAIN OUTCOME MEASURES Pref-1, monocyte chemotactic protein-1, TNF-α, granulocyte colony-stimulating factor, IL-6, and adiponectin levels, macrophage numbers, and adipocyte size were measured in omental and subcutaneous adipose tissue. RESULTS The MHO group had a lower level of Pref-1 (per 1000 adipocytes) in both subcutaneous [160 (136-177) versus 194 (153-355); P < 0.05] and omental adipose tissue [102 (32-175) versus 194 (100-350); P < 0.005]. This was associated with lower numbers of macrophages, lower levels of TNF-α, monocyte chemotactic protein-1, and granulocyte colony-stimulating factor, and higher levels of adiponectin. Omental Pref-1 showed strong correlations with adipocyte size (r = 0.67, P < 0.0005) and metabolic and adipokine parameters, including percent fatty liver (r = 0.62, P < 0.005), fasting glucose (r = 0.68, P < 0.0005), triglyceride (r = 0.60, P < 0.005), high-density lipoprotein cholesterol (r = -0.46, P < 0.05), and adiponectin (r = -0.71, P < 0.05). CONCLUSION Adipose tissue in MHO individuals had lower levels of Pref-1, a known inhibitor of preadipocyte differentiation, and a more favorable inflammatory profile. These factors may be key to protecting this subgroup of obese individuals from the adverse metabolic profile associated with excess adiposity.

Altered Distribution and Increased IL-17 Production by Mucosal-Associated Invariant T Cells in Adult and Childhood Obesity

Mucosal-associated invariant T (MAIT) cells are innate MHC-unrestricted cells that regulate inflammatory responses through the rapid production of cytokines. In this article, we show that circulating MAIT cells are depleted in obese adults, and depletion is associated with diabetic status. Circulating MAIT cells more frequently produced IL-17 upon stimulation ex vivo, a cytokine implicated in insulin resistance. MAIT cells were enriched in adipose tissue (AT) compared with blood. AT MAIT cells, but not circulating MAIT cells, were capable of producing IL-10. In AT from obese subjects, MAIT cells were depleted, were less likely to produce IL-10, and more frequently produced IL-17. Finally, we show that IL-17+ MAIT cells are also increased in childhood obesity, and altered MAIT cell frequencies in obese children are positively associated with insulin resistance. These data indicate that MAIT cells are enriched in human AT and display an IL-17+ phenotype in both obese adults and children, correlating with levels of insulin resistance. The alterations in MAIT cells may be contributing to obesity-related sterile inflammation and insulin resistance.

The Impact of Childhood Obesity on Inflammation, Innate Immune Cell Frequency, and Metabolic MicroRNA Expression

BACKGROUND Obesity is characterized by chronic inflammation, immune dysregulation, and alteration of gene expression, associated with type 2 diabetes mellitus and cardiovascular disease. The degree to which these changes occur in childhood obesity is not fully defined. AIMS AND METHODS The aim was to investigate the effect of childhood obesity on immune cell frequency, macrophage activation, cytokine production, and specific regulators of metabolic gene expression. Profiling was performed on peripheral blood from 29 obese and 20 nonobese children using real-time PCR, ELISA, and flow cytometry. RESULTS Fasting glucose was similar in both groups, but there was a higher degree of insulin resistance in obese subjects (homeostasis model of assessment for insulin resistance, 4.8 vs 0.84; P < .001). Soluble CD163, a marker of macrophage polarization to a proinflammatory profile, was elevated in the obese compared to nonobese children (135 vs 105 ng/mL; P = .03). Invariant natural killer T cells were reduced in the obese children (CD3 T cells, 0.31 vs 0.53%; P = .001). Cytokine profiling revealed significantly elevated TNF-α (6.7 vs 5.1 pg/mL; P = .01) and leptin (1186 vs 432 pg/mL; P < .001) and reduced adiponectin (884 vs 1321 pg/mL; P = .001) in obese compared to nonobese children. Stimulation of peripheral blood mononuclear cells from obese children resulted in higher levels of IL-1β (2100 vs 1500 pg/mL; P = .018). There was a 4-fold increase in expression of microRNA33a (P = .001) and a 3-fold increase in microRNA33b (P = .017) in obese children. CONCLUSION Childhood obesity is associated with changes in immune cell frequency, inflammatory environment, and regulation of metabolic gene expression. These changes have been causally linked to the onset of metabolic disease in adulthood and suggest the future trajectory of obese children to the development of type 2 diabetes mellitus and premature cardiovascular disease.

Glucagon-like peptide-1 analogue therapy for psoriasis patients with obesity and type 2 diabetes: a prospective cohort study.

Background  Diabetes and obesity are more prevalent amongst psoriasis patients as is disturbance of the innate immune system. GLP‐1 analogue therapy considerably improves weight and glycaemic control in people with type 2 diabetes and its receptor is present on innate immune cells.

Human Invariant NKT Cell Subsets Differentially Promote Differentiation, Antibody Production, and T Cell Stimulation by B Cells In Vitro

Invariant NK T (iNKT) cells can provide help for B cell activation and Ab production. Because B cells are also capable of cytokine production, Ag presentation, and T cell activation, we hypothesized that iNKT cells will also influence these activities. Furthermore, subsets of iNKT cells based on CD4 and CD8 expression that have distinct functional activities may differentially affect B cell functions. We investigated the effects of coculturing expanded human CD4+, CD8α+, and CD4−CD8α− double-negative (DN) iNKT cells with autologous peripheral B cells in vitro. All iNKT cell subsets induced IgM, IgA, and IgG release by B cells without needing the iNKT cell agonist ligand α-galactosylceramide. Additionally, CD4+ iNKT cells induced expansions of cells with phenotypes of regulatory B cells. When cocultured with α-galactosylceramide–pulsed B cells, CD4+ and DN iNKT cells secreted Th1 and Th2 cytokines but at 10–1000-fold lower levels than when cultured with dendritic cells. CD4+ iNKT cells reciprocally induced IL-4 and IL-10 production by B cells. DN iNKT cells expressed the cytotoxic degranulation marker CD107a upon exposure to B cells. Remarkably, whereas iNKT cell subsets could induce CD40 and CD86 expression by B cells, iNKT cell–matured B cells were unable to drive proliferation of autologous and alloreactive conventional T cells, as seen with B cells cultured in the absence of iNKT cells. Therefore, human CD4+, CD8α+, and DN iNKT cells can differentially promote and regulate the induction of Ab and T cell responses by B cells.

Adipose Type One Innate Lymphoid Cells Regulate Macrophage Homeostasis through Targeted Cytotoxicity

SUMMARY Adipose tissue has a dynamic immune system that adapts to changes in diet and maintains homeostatic tissue remodeling. Adipose type 1 innate lymphoid cells (AT1‐ILCs) promote pro‐inflammatory macrophages in obesity, but little is known about their functions at steady state. Here we found that human and murine adipose tissue harbor heterogeneous populations of AT1‐ILCs. Experiments using parabiotic mice fed a high‐fat diet (HFD) showed differential trafficking of AT1‐ILCs, particularly in response to short‐ and long‐term HFD and diet restriction. At steady state, AT1‐ILCs displayed cytotoxic activity toward adipose tissue macrophages (ATMs). Depletion of AT1‐ILCs and perforin deficiency resulted in alterations in the ratio of inflammatory to anti‐inflammatory ATMs, and adoptive transfer of AT1‐ILCs exacerbated metabolic disorder. Diet‐induced obesity impaired AT1‐ILC killing ability. Our findings reveal a role for AT1‐ILCs in regulating ATM homeostasis through cytotoxicity and suggest that this function is relevant in both homeostasis and metabolic disease. Graphical Abstract Figure. No Caption available. HighlightsAT1‐ILCs are enriched in mouse and human adipose tissue and are predominantly tissue residentAT1‐ILCs kill adipose tissue macrophages (ATMs) and maintain ATM homeostasisSubsets of AT1‐ILCs infiltrate adipose tissue during the onset of obesityIn obesity, AT1‐ILCs are reduced and lose their ability to kill &NA; Boulenouar et al. define different subsets of type 1 innate lymphoid cells (AT1‐ILCs) in human and murine adipose tissues and show that at steady state, AT1‐ILCs kill adipose tissue macrophages (ATMs). In obesity, cytotoxicity is impaired. Interference with AT1‐ILC cytotoxicity impacted ATM homeostasis and systemic metabolism, pointing to its importance in homeostasis and disease.

Changes in human dendritic cell number and function in severe obesity may contribute to increased susceptibility to viral infection

Dendritic cells (DCs) are key immune sentinels linking the innate and adaptive immune systems. DCs recognise danger signals and initiate T-cell tolerance, memory and polarisation. They are critical cells in responding to a viral illness. Obese individuals have been shown to have an impaired response to vaccinations against virally mediated conditions and to have an increased susceptibility to multi-organ failure in response to viral illness. We investigated if DCs are altered in an obese cohort (mean body mass index 51.7±7.3 kg m−2), ultimately resulting in differential T-cell responses. Circulating DCs were found to be significantly decreased in the obese compared with the lean cohort (0.82% vs 2.53%). Following Toll-like receptor stimulation, compared with lean controls, DCs generated from the obese cohort upregulated significantly less CD83 (40% vs 17% mean fluorescence intensity), a molecule implicated in the elicitation of T-cell responses, particularly viral responses. Obese DCs produced twofold more of the immunosuppressive cytokine interleukin (IL)-10 than lean controls, and in turn stimulated fourfold more IL-4-production from allogenic naive T cells. We conclude that obesity negatively impacts the ability of DCs to mature and elicit appropriate T-cell responses to a general stimulus. This may contribute to the increased susceptibility to viral infection observed in severe obesity.