Prolonged proinflammatory cytokine production in monocytes modulated by interleukin 10 after influenza vaccination in older adults

We evaluated in vivo innate immune responses in monocyte populations from 67 young (aged 21-30 years) and older (aged ≥65 years) adults before and after influenza vaccination. CD14(+)CD16(+) inflammatory monocytes were induced after vaccination in both young and older adults. In classical CD14(+)CD16(-) and inflammatory monocytes, production of tumor necrosis factor α and interleukin 6, as measured by intracellular staining, was strongly induced after vaccination. Cytokine production was strongly associated with influenza vaccine antibody response; the highest levels were found as late as day 28 after vaccination in young subjects and were substantially diminished in older subjects. Notably, levels of the anti-inflammatory cytokine interleukin 10 (IL-10) were markedly elevated in monocytes from older subjects before and after vaccination. In purified monocytes, we found age-associated elevation in phosphorylated signal transducer and activator of transcription-3, and decreased serine 359 phosphorylation of the negative IL-10 regulator dual-specificity phosphatase 1. These findings for the first time implicate dysregulated IL-10 production in impaired vaccine responses in older adults.

Common genetic variants modulate pathogen-sensing responses in human dendritic cells

Little is known about how human genetic variation affects the responses to environmental stimuli in the context of complex diseases. Experimental and computational approaches were applied to determine the effects of genetic variation on the induction of pathogen-responsive genes in human dendritic cells. We identified 121 common genetic variants associated in cis with variation in expression responses to Escherichia coli lipopolysaccharide, influenza, or interferon-β (IFN-β). We localized and validated causal variants to binding sites of pathogen-activated STAT (signal transducer and activator of transcription) and IRF (IFN-regulatory factor) transcription factors. We also identified a common variant in IRF7 that is associated in trans with type I IFN induction in response to influenza infection. Our results reveal common alleles that explain interindividual variation in pathogen sensing and provide functional annotation for genetic variants that alter susceptibility to inflammatory diseases.

Increased Th17 response to myelin peptides in pediatric MS

Studies of the underlying immune mechanisms of multiple sclerosis (MS) in children may shed light on the initial events of MS pathogenesis. We studied T cell responses to myelin peptides in 10 pediatric MS patients (PMS), 10 pediatric healthy controls (PHC), 10 adult MS patients (AMS) and 10 adult healthy controls (AHC). A significantly higher proportion of divided CD4+ T cell responses in response to myelin peptides by the CFSE assay in PMS compared to PHC at both concentrations of myelin peptide tested (t test, 95% CI, p=0.0067 for MP1; p=0.0086 for MP10), and between PMS and AMS (p=0.0012 at 1 μg/mL of myelin peptides, p<0.0001 at 10 μg/mL) was found. In addition, T cells with a central memory phenotype producing IL-17 were increased in PMS compared to PHC (p<0.05). IL-7 levels in culture supernatants were elevated in PMS compared to PHC and AMS (t test<0.01).

Increased frequencies of myelin oligodendrocyte glycoprotein/MHC class II-binding CD4 cells in patients with multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disease characterized by infiltration of pathogenic immune cells in the CNS resulting in destruction of the myelin sheath and surrounding axons. We and others have previously measured the frequency of human myelin-reactive T cells in peripheral blood. Using T cell cloning techniques, a modest increase in the frequency of myelin-reactive T cells in patients as compared with control subjects was observed. In this study, we investigated whether myelin oligodendrocyte glycoprotein (MOG)-specific T cells could be detected and their frequency was measured using DRB1*0401/MOG(97-109(107E-S)) tetramers in MS subjects and healthy controls expressing HLA class II DRB1*0401. We defined the optimal culture conditions for expansion of MOG-reactive T cells upon MOG peptide stimulation of PMBCs. MOG(97-109)-reactive CD4(+) T cells, isolated with DRB1*0401/MOG(97-109) tetramers, and after a short-term culture of PMBCs with MOG(97-109) peptides, were detected more frequently from patients with MS as compared with healthy controls. T cell clones from single cell cloning of DRB1*0401/MOG(97-109(107E-S)) tetramer(+) cells confirmed that these T cell clones were responsive to both the native and the substituted MOG peptide. These data indicate that autoantigen-specific T cells can be detected and enumerated from the blood of subjects using class II tetramers, and the frequency of MOG(97-109)-reactive T cells is greater in patients with MS as compared with healthy controls.

Impaired thymic tolerance to α-myosin directs autoimmunity to the heart in mice and humans

Autoimmunity has long been linked to myocarditis and its sequela, dilated cardiomyopathy, the leading causes of heart failure in young patients. However, the underlying mechanisms are poorly defined, with most clinical investigations focused on humoral autoimmunity as the target for intervention. Here, we show that the α-isoform of myosin heavy chain (α-MyHC, which is encoded by the gene Myh6) is the pathogenic autoantigen for CD4+ T cells in a spontaneous mouse model of myocarditis. Further, we found that Myh6 transcripts were absent in mouse medullary thymic epithelial cells (mTECs) and peripheral lymphoid stromal cells, which have been implicated in mediating central and peripheral T cell tolerance, respectively. Transgenic expression of α-MyHC in thymic epithelium conferred tolerance to cardiac myosin and prevented myocarditis, demonstrating that α-MyHC is a primary autoantigen in this disease process. Remarkably, we found that humans also lacked α-MyHC in mTECs and had high frequencies of α-MyHC-specific T cells in peripheral blood, with markedly augmented T cell responses to α-MyHC in patients with myocarditis. Since α-MyHC constitutes a small fraction of MyHC in human heart, these findings challenge the longstanding notion that autoimmune targeting of MyHC is due to its cardiac abundance and instead suggest that it is targeted as a result of impaired T cell tolerance mechanisms. These results thus support a role for T cell-specific therapies for myocarditis.

On-chip activation and subsequent detection of individual antigen-specific T cells

The frequencies of antigen-specific CD4+ T cells in samples of human tissue have been difficult to determine accurately ex vivo, particularly for autoimmune diseases such as multiple sclerosis or type 1 diabetes. Conventional approaches involve the expansion of primary T cells in vitro to increase the numbers of cells, and a subsequent assessment of the frequencies of antigen-specific T cells in the expanded population by limiting dilution or by using fluorescently labeled tetramers of peptide-loaded major histocompatibility complex (MHC) receptors. Here we describe an alternative approach that uses arrays of subnanoliter wells coated with recombinant peptide-loaded MHC class II monomers to isolate and stimulate individual CD4+ T cells in an antigen-specific manner. In these experiments, activation was monitored using microengraving to capture two cytokines (IFNgamma and IL-17) released from single cells. This new method should enable direct enumeration of antigen-specific CD4+ T cells ex vivo from clinical samples.

Monocytes from patients with type 1 diabetes spontaneously secrete proinflammatory cytokines inducing Th17 cells

Autoimmune diseases including type 1 diabetes (T1D) are thought to have a Th1/Th17 bias. The underlying mechanisms driving the activation and differentiation of these proinflammatory T cells are unknown. We examined the monocytes isolated directly from the blood of T1D patients and found they spontaneously secreted the proinflammatory cytokines IL-1beta and IL-6, which are known to induce and expand Th17 cells. Moreover, these in vivo-activated monocytes from T1D subjects induced more IL-17-secreting cells from memory T cells compared with monocytes from healthy control subjects. The induction of IL-17-secreting T cells by monocytes from T1D subjects was reduced in vitro with a combination of an IL-6-blocking Ab and IL-1R antagonist. In this study, we report a significant although modest increase in the frequency of IL-17-secreting cells in lymphocytes from long-term patients with T1D compared with healthy controls. These data suggest that the innate immune system in T1D may drive the adaptive immune system by expanding the Th17 population of effector T cells.

Differential gene expression profiles are dependent upon method of peripheral blood collection and RNA isolation

BACKGROUND

RNA isolation and purification steps greatly influence the results of gene expression profiling. There are two commercially available products for whole blood RNA collection, PAXgene and Tempus blood collection tubes, and each comes with their own RNA purification method. In both systems the blood is immediately lysed when collected into the tube and RNA stabilized using proprietary reagents. Both systems enable minimal blood handling procedures thus minimizing the risk of inducing changes in gene expression through blood handling or processing. Because the RNA purification steps could influence the total RNA pool, we examined the impact of RNA isolation, using the PAXgene or Tempus method, on gene expression profiles.

RESULTS

Using microarrays as readout of RNA from stimulated whole blood we found a common set of expressed transcripts in RNA samples from either PAXgene or Tempus. However, we also found several to be uniquely expressed depending on the type of collection tube, suggesting that RNA purification methods impact results of differential gene expression profiling. Specifically, transcripts for several known PHA-inducible genes, including IFNgamma, IL13, IL2, IL3, and IL4 were found to be upregulated in stimulated vs. control samples when RNA was isolated using the ABI Tempus method, but not using the PAXgene method (p < 0.01, FDR corrected). Sequenom Quantiative Gene Expression (QGE) (SanDiego, CA) measures confirmed IL2, IL4 and IFNgamma up-regulation in Tempus purified RNA from PHA stimulated cells while only IL2 was up-regulated using PAXgene purified (p < 0.05).

CONCLUSION

Here, we demonstrate that peripheral blood RNA isolation methods can critically impact differential expression results, particularly in the clinical setting where fold-change differences are typically small and there is inherent variability within biological cohorts. A modified method based upon the Tempus system was found to provide high yield, good post-hybridization array quality, low variability in expression measures and was shown to produce differential expression results consistent with the predicted immunologic effects of PHA stimulation.

Distinct functions of autoreactive memory and effector CD4+ T cells in experimental autoimmune encephalomyelitis

The persistence of human autoimmune diseases is thought to be mediated predominantly by memory T cells. We investigated the phenotype and migration of memory versus effector T cells in vivo in experimental autoimmune encephalomyelitis (EAE). We found that memory CD4(+) T cells up-regulated the activation marker CD44 as well as CXCR3 and ICOS, proliferated more and produced more interferon-gamma and less interleukin-17 compared to effector T cells. Moreover, adoptive transfer of memory T cells into T cell receptor (TCR)alphabeta(-/-) recipients induced more severe disease than did effector CD4(+) T cells with marked central nervous system inflammation and axonal damage. The uniqueness of disease mediated by memory T cells was confirmed by the differential susceptibility to immunomodulatory therapies in vivo. CD28-B7 T cell costimulatory signal blockade by CTLA4Ig suppressed effector cell-mediated EAE but had minimal effects on disease induced by memory cells. In contrast, ICOS-B7h blockade exacerbated effector T cell-induced EAE but protected from disease induced by memory T cells. However, blockade of the OX40 (CD134) costimulatory pathway ameliorated disease mediated by both memory and effector T cells. Our data extend the understanding of the pathogenicity of autoreactive memory T cells and have important implications for the development of novel therapies for human autoimmune diseases.

Elevated neuronal expression of CD200 protects Wlds mice from inflammation-mediated neurodegeneration

Axonal damage secondary to inflammation is likely the substrate of chronic disability in multiple sclerosis and is found in the animal model of experimental autoimmune encephalomyelitis (EAE). Wld(s) mice have a triplication of the fusion gene Ube4b/Nmnat and a phenotype of axon protection. Wld(s) mice develop an attenuated disease course of EAE, with decreased demyelination, reduced axonal pathology, and decreased central nervous system (CNS) macrophage and microglial accumulation. We show that attenuated disease in Wld(s) mice was associated with robust constitutive expression of the nonsignaling CD200 molecule on neurons in the CNS compared with control mice. CD200 interacts with its signaling receptor CD200R, which we found to be expressed on microglia, astrocytes, and oligodendrocytes at similar levels in control and Wld(s) mice. Administration of blocking anti-CD200 antibody to Wld(s) mice abrogated disease attenuation and was associated with increased CNS inflammation and neurodegeneration. In vitro, Wld(s) neuronal cultures were protected from microglial-induced neurotoxicity compared with control cultures, but protection was abrogated by anti-CD200 antibody. The CD200-CD200R pathway plays a critical role in attenuating EAE and reducing inflammation-mediated damage in the CNS. Strategies that up-regulate the expression of CD200 in the CNS or molecules that ligate the CD200R may be relevant as neuroprotective strategies in multiple sclerosis.

The cell cycle associated protein, HTm4, is expressed in differentiating cellsof the hematopoietic and central nervous system in mice

HTm4 is a member of a newly defined family of human and murine proteins, the MS4 (membrane-spanning four) protein group, which has a distinctive four-transmembrane structure. MS4 protein functions include roles as cell surface signaling receptors and intracellular adapter proteins. We have previously demonstrated that HTm4 regulates the function of the KAP phosphatase, a key regulator of cell cycle progression. In humans, the expression of HTm4 is largely restricted to cells of the hematopoietic lineage, possibly reflecting a causal role for this molecule in differentiation/proliferation of hematopoietic lineage cells. In this study, we show that, like the human homologue, murine HTm4 is also predominantly a hematopoietic protein with distinctive expression patterns in developing murine embryos and in adult animals. In addition, we observed that murine HTm4 is highly expressed in the developing and adult murine nervous system, suggesting a previously unrecognized role in central and peripheral nervous system development.