The Role of Activating Protein 1 in the Transcriptional Regulation of the Human FCGR2B Promoter Mediated by the -343 G → C Polymorphism Associated with Systemic Lupus Erythematosus

Study of hub nodes of transcription factor-target gene regulatory network and immune mechanism for type 2 diabetes based on chip analysis of GEO database

Identification of novel therapeutic targets for type 2 diabetes is a key area of contemporary research. In this study, we screened differentially expressed genes in type 2 diabetes through the GEO database and sought to identify the key virulence factors for type 2 diabetes through a transcription factor regulatory network. Our findings may help identify new therapeutic targets for type 2 diabetes. Data pertaining to the humoral (whole blood) gene expression profile of diabetic patients were obtained from the NCBI's GEO Datasets database and gene sets with differential expression were identified. Subsequently, the TRED transcriptional regulatory element database was integrated to build a gene regulatory network for type 2 diabetes. Functional analysis (GO-Analysis) and Pathway-analysis of differentially expressed genes were performed using the DAVID database and the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Finally, gene-disease correlation analysis was performed using the DAVID online annotation tool. A total of 236 pathogenic genes, four transcription factors related to the pathogenic genes, and 261 corresponding target genes were identified. A transcription factor-target gene regulatory network for type 2 diabetes was constructed. Most of the key factors of the transcription factor-target gene regulatory network for type 2 diabetes were found closely related to the immune metabolic system and the functions of cell proliferation and transformation.

Six macrophage-associated genes in synovium constitute a novel diagnostic signature for osteoarthritis

Background

Synovial macrophages play important roles in the formation and progression of osteoarthritis (OA). This study aimed to explore the biological and clinical significance of macrophage-associated genes (MAGs) in OA.

Methods

The OA synovial gene expression profiles GSE89408 and GSE82107 were obtained from the GEO database. Single-sample gene set enrichment analysis (ssGSEA) and GSEA were employed to decipher differences in immune infiltration and macrophage-associated biological pathways, respectively. Protein–protein interaction (PPI) network analysis and machine learning were utilized to establish a macrophage-associated gene diagnostic signature (MAGDS). RT-qPCR was performed to test the expression of key MAGs in murine models.

Results

OA synovium presented high levels of immune infiltration and activation of macrophage-associated biological pathways. A total of 55 differentially expressed MAGs were identified. Using PPI analysis and machine learning, a MAGDS consisting of IL1B, C5AR1, FCGR2B, IL10, IL6, and TYROBP was established for OA diagnosis (AUC = 0.910) and molecular pathological evaluation. Patients with high MAGDS scores may possess higher levels of immune infiltration and expression of matrix metalloproteinases (MMPs), implying poor biological alterations. The diagnostic value of MAGDS was also validated in an external cohort (AUC = 0.886). The expression of key MAGs was validated in a murine model using RT-qPCR. Additionally, a competitive endogenous RNA network was constructed to reveal the potential posttranscriptional regulatory mechanisms.

Conclusions

We developed and validated a MAGDS model with the ability to accurately diagnose and characterize biological alterations in OA. The six key MAGs may also be latent targets for immunoregulatory therapy.

FcɣRIIB regulates autoantibody responses by limiting marginal zone B cell activation

FcɣRIIB is an inhibitory receptor expressed throughout B cell development. Diminished expression or function is associated with lupus in mice and humans, in particular through an effect on autoantibody production and plasma cell differentiation. Here, we analysed the effect of B cell-intrinsic FcɣRIIB expression on B cell activation and plasma cell differentiation. Loss of FcɣRIIB on B cells (Fcgr2b cKO mice) led to a spontaneous increase in autoantibody titers. This increase was most striking for IgG3, suggestive of increased extrafollicular responses. Marginal zone (MZ) B cells had the highest expression of FcɣRIIB in both mouse and human. This high expression of FcɣRIIB was linked to increased MZ B cell activation, Erk phosphorylation, and calcium fluxin the absence of FcɣRIIB triggering. Marked increases in IgG3+ plasma cells and B cells were observed during extrafollicular plasma cell responses in Fcgr2b cKO mice. The increased IgG3 response following immunization of Fcgr2b cKO mice was lost in MZ-deficient Notch2/Fcgr2b cKO mice. Importantly, SLE patients exhibited decreased expression of FcɣRIIB, most strongly in MZ B cells. Thus, we present a model where high FcɣRIIB expression in MZ B cells prevents their hyperactivation and ensuing autoimmunity.

HIF activation enhances FcγRIIb expression on mononuclear phagocytes impeding tumor targeting antibody immunotherapy

BACKGROUND

Hypoxia is a hallmark of the tumor microenvironment (TME) and in addition to altering metabolism in cancer cells, it transforms tumor-associated stromal cells. Within the tumor stromal cell compartment, tumor-associated macrophages (TAMs) provide potent pro-tumoral support. However, TAMs can also be harnessed to destroy tumor cells by monoclonal antibody (mAb) immunotherapy, through antibody dependent cellular phagocytosis (ADCP). This is mediated via antibody-binding activating Fc gamma receptors (FcγR) and impaired by the single inhibitory FcγR, FcγRIIb.

METHODS

We applied a multi-OMIC approach coupled with in vitro functional assays and murine tumor models to assess the effects of hypoxia inducible factor (HIF) activation on mAb mediated depletion of human and murine cancer cells. For mechanistic assessments, siRNA-mediated gene silencing, Western blotting and chromatin immune precipitation were utilized to assess the impact of identified regulators on FCGR2B gene transcription.

RESULTS

We report that TAMs are FcγRIIbbright relative to healthy tissue counterparts and under hypoxic conditions, mononuclear phagocytes markedly upregulate FcγRIIb. This enhanced FcγRIIb expression is transcriptionally driven through HIFs and Activator protein 1 (AP-1). Importantly, this phenotype reduces the ability of macrophages to eliminate anti-CD20 monoclonal antibody (mAb) opsonized human chronic lymphocytic leukemia cells in vitro and EL4 lymphoma cells in vivo in human FcγRIIb+/+ transgenic mice. Furthermore, post-HIF activation, mAb mediated blockade of FcγRIIb can partially restore phagocytic function in human monocytes.

CONCLUSION

Our findings provide a detailed molecular and cellular basis for hypoxia driven resistance to antitumor mAb immunotherapy, unveiling a hitherto unexplored aspect of the TME. These findings provide a mechanistic rationale for the modulation of FcγRIIb expression or its blockade as a promising strategy to enhance approved and novel mAb immunotherapies.

Data Mining Mycobacterium tuberculosis Pathogenic Gene Transcription Factors and Their Regulatory Network Nodes

Tuberculosis (TB) is one of the deadliest infectious diseases worldwide. In Mycobacterium tuberculosis, changes in gene expression are highly variable and involve many genes, so traditional single-gene screening of M. tuberculosis targets has been unable to meet the needs of clinical diagnosis. In this study, using the National Center for Biotechnology Information (NCBI) GEO Datasets, whole blood gene expression profile data were obtained in patients with active pulmonary tuberculosis. Linear model-experience Bayesian statistics using the Limma package in R combined with t-tests were applied for nonspecific filtration of the expression profile data, and the differentially expressed human genes were determined. Using DAVID and KEGG, the functional analysis of differentially expressed genes (GO analysis) and the analysis of signaling pathways were performed. Based on the differentially expressed gene, the transcriptional regulatory element databases (TRED) were integrated to construct the M. tuberculosis pathogenic gene regulatory network, and the correlation of the network genes with disease was analyzed with the DAVID online annotation tool. It was predicted that IL-6, JUN, and TP53, along with transcription factors SRC, TNF, and MAPK14, could regulate the immune response, with their function being extracellular region activity and protein binding during infection with M. tuberculosis.

Deregulated Fcγ receptor expression in patients with CIDP

Objective:

To evaluate the expression of activating and inhibitory Fc-gamma receptors (FcγRs) before and during clinically effective therapy with IV immunoglobulin (IVIg) in patients with chronic inflammatory demyelinating polyneuropathy (CIDP).

Methods:

Peripheral blood leukocyte subsets, including classical CD14^highCD16⁻ and nonclassical inflammatory CD14^lowCD16⁺ monocytes as well as naive CD19⁺CD27⁻ and memory CD19⁺CD27⁺ B cells, were obtained at baseline and monitored at 2 and 4–8 weeks after initiation of IVIg therapy.

Results:

Compared with healthy donors matched by age and sex, patients with CIDP showed increased expression levels of the activating high-affinity FcγR1 on CD14^highCD16⁻ (p < 0.001) and CD14^lowCD16⁺ monocytes (p < 0.001). Expression of the activating low-affinity FcγRIIA was increased on CD14^lowCD16⁺ monocytes (p = 0.023). Conversely, expression of the inhibitory FcγRIIB was reduced on naive (p = 0.009) and memory (p = 0.002) B cells as well as on CD14^highCD16⁻ monocytes (p = 0.046). Clinically effective IVIg therapy partially restored deregulated FcγR expression on B cell subsets and monocytes.

Conclusions:

The FcγR regulatory system is disturbed in patients with CIDP. Balancing activating vs inhibitory FcγR expression might provide a clinical benefit for patients with CIDP.

Human FcR polymorphism and disease

Fc receptors play a central role in maintaining the homeostatic balance in the immune system. Our knowledge of the structure and function of these receptors and their naturally occurring polymorphisms, including single nucleotide polymorphisms and/or copy number variations, continues to expand. Through studies of their impact on human biology and clinical phenotype, the contributions of these variants to the pathogenesis, progression, and/or treatment outcome of many diseases that involve immunoglobulin have become evident. They affect susceptibility to bacterial and viral pathogens, constitute as risk factors for IgG or IgE mediated inflammatory diseases, and impact the development of many autoimmune conditions. In this chapter, we will provide an overview of these genetic variations in classical FcγRs, FcRLs, and other Fc receptors, as well as challenges in achieving an accurate and comprehensive understanding of the FcR polymorphisms and genomic architecture.

Genetic variants in CCNB1 associated with differential gene transcription and risk of coronary in-stent restenosis

BACKGROUND

The development of diagnostic tools to assess restenosis risk after stent deployment may enable the intervention to be tailored to the individual patient, for example, by targeting the use of drug-eluting stent to high-risk patients, with the goal of improving safety and reducing costs. The CCNB1 gene (encoding cyclin B1) positively regulates cell proliferation, a key component of in-stent restenosis. Therefore, we hypothesized that single-nucleotide polymorphisms in CCNB1 may serve as useful tools in risk stratification for in-stent restenosis.

METHODS AND RESULTS

We identified 3 single-nucleotide polymorphisms in CCNB1 associated with increased restenosis risk in a cohort of 284 patients undergoing coronary angioplasty and stent placement (rs350099: TT versus CC+TC; odds ratio [OR], 1.82; 95% confidence interval [CI], 1.09-3.03; P=0.023; rs350104: CC versus CT+TT; OR, 1.82; 95% CI, 1.02-3.26; P=0.040; and rs164390: GG versus GT+TT; OR, 2.27; 95% CI, 1.33-3.85; P=0.002). These findings were replicated in another cohort study of 715 patients (rs350099: TT versus CC+TC; OR, 1.88; 95% CI, 0.92-3.81; P=0.080; rs350104: CC versus CT+TT; OR, 2.23; 95% CI, 1.18-4.25; P=0.016; and rs164390: GG versus GT+TT; OR, 1.87; 95% CI, 1.03-3.47; P=0.040). Moreover, the haplotype containing all 3 risk alleles is associated with higher CCNB1 mRNA expression in circulating lymphocytes and increased in-stent restenosis risk (OR, 1.43; 95% CI, 1.00-1.823; P=0.039). The risk variants of rs350099, rs350104, and rs164390 are associated with increased reporter gene expression through binding of transcription factors nuclear factor-Y, activator protein 1, and specificity protein 1, respectively.

CONCLUSIONS

Allele-dependent transcriptional regulation of CCNB1 associated with rs350099, rs350104, and rs164390 affects the risk of in-stent restenosis. These findings reveal these common genetic variations as attractive diagnostic tools in risk stratification for restenosis.

FcγRIIb mediates amyloid-β neurotoxicity and memory impairment in Alzheimer's disease

Amyloid-β (Aβ) induces neuronal loss and cognitive deficits and is believed to be a prominent cause of Alzheimer's disease (AD); however, the cellular pathology of the disease is not fully understood. Here, we report that IgG Fcγ receptor II-b (FcγRIIb) mediates Aβ neurotoxicity and neurodegeneration. We found that FcγRIIb is significantly upregulated in the hippocampus of AD brains and neuronal cells exposed to synthetic Aβ. Neuronal FcγRIIb activated ER stress and caspase-12, and Fcgr2b KO primary neurons were resistant to synthetic Aβ-induced cell death in vitro. Fcgr2b deficiency ameliorated Aβ-induced inhibition of long-term potentiation and inhibited the reduction of synaptic density by naturally secreted Aβ. Moreover, genetic depletion of Fcgr2b rescued memory impairments in an AD mouse model. To determine the mechanism of action of FcγRIIb in Aβ neurotoxicity, we demonstrated that soluble Aβ oligomers interact with FcγRIIb in vitro and in AD brains, and that inhibition of their interaction blocks synthetic Aβ neurotoxicity. We conclude that FcγRIIb has an aberrant, but essential, role in Aβ-mediated neuronal dysfunction.

Analysis of a wild mouse promoter variant reveals a novel role for FcγRIIb in the control of the germinal center and autoimmunity

Genetic variants of the inhibitory Fc receptor FcγRIIb have been associated with systemic lupus erythematosus in humans and mice. The mechanism by which Fcgr2b variants contribute to the development of autoimmunity is unknown and was investigated by knocking in the most commonly conserved wild mouse Fcgr2b promoter haplotype, also associated with autoimmune-prone mouse strains, into the C57BL/6 background. We found that in the absence of an AP-1-binding site in its promoter, FcγRIIb failed to be up-regulated on activated and germinal center (GC) B cells. This resulted in enhanced GC responses, increased affinity maturation, and autoantibody production. Accordingly, in the absence of FcγRIIb activation-induced up-regulation, mice developed more severe collagen-induced arthritis and spontaneous glomerular immune complex deposition. Our data highlight how natural variation in Fcgr2b drives the development of autoimmune disease. They also show how the study of such variants using a knockin approach can provide insight into immune mechanisms not possible using conventional genetic manipulation, in this case demonstrating an unexpected critical role for the activation-induced up-regulation of FcγRIIb in controlling affinity maturation, autoantibody production, and autoimmunity.

Association of c-Jun gene polymorphism with susceptibility to systemic lupus erythematosus in a Chinese population

C-Jun has been proved as playing an important role in the pathogenesis of tumors, as a main component of Activator protein 1 and c-Jun gene polymorphisms are associated with colorectal cancer. However, the relationship between the c-Jun gene polymorphism and the susceptibility to systemic lupus erythematosus (SLE) has not been known. Our purpose is to evaluate whether the c-Jun gene polymorphism (SNP rs3748814) is associated with susceptibility to SLE in a Chinese population. In this study, we enrolled 502 SLE patients and 652 healthy controls. The c-Jun polymorphism (rs3748814) was specified from genomic DNA using the TaqMan genotyping assay on a 7300 real-time reverse transcription polymerase chain reaction system. We found that the frequency of the A/G genotype in SLE patients was lower than in healthy controls, whereas the frequency of the G/G genotype was significantly higher in SLE patients than in healthy controls (A/G vs. G/G p = 8.670e-08, odds ratio [OR] = 0.290, 95% confidence interval [CI] = 0.184-0.456). In addition, the frequency of allele A in the patients group was significantly lower than in the control group (A vs. G p=5.221e-09, OR = 0.308, 95% CI = 0.212-0.466). The distribution of genotype and allele frequency in SLE patients with lupus nephritis (LN) compared with SLE patients without LN was not statistically significant (A/G vs. G/G p = 0.744, OR = 1.157, 95% CI=0.481-2.785; A vs. G p = 0.748, OR = 1.152, 95% CI = 0.486-2.734; A/A+A/G vs. G/G p = 0.744, OR = 1.157, 95% CI = 0.481-2.785). Furthermore, we did not find any significant association between other clinical features and genotypes. Our findings suggest that the c-Jun polymorphism (rs3748814) may be significantly associated with the susceptibility to SLE in a Chinese population.

Aim2 deficiency in mice suppresses the expression of the inhibitory Fcgamma receptor (FcgammaRIIB) through the induction of the IFN-inducible p202, a lupus susceptibility protein

Murine Aim2 and Ifi202 genes (encoding for the Aim2 and p202 proteins) are members of the IFN-inducible Ifi200 gene family. The Aim2 deficiency in mice activates IFN signaling and stimulates the expression of the lupus susceptibility gene, the Ifi202, located within the NZB autoimmunity 2 (Nba2) interval. Given that the deficiency in the expression of the Fcgr2b gene (encoding for the inhibitory FcγRIIB receptor) is associated with increased lupus susceptibility in mice, we investigated whether the Aim2 protein could regulate the expression of Fcgr2b gene. In this article, we report that Aim2 deficiency in mice suppresses the expression of the FcγRIIB receptor. Interestingly, the Fcgr2b-deficient cells expressed increased levels of the IFN-β, activated IFN signaling, and expressed reduced levels of the Aim2 protein. Treatment of splenic cells with IFN-α or -γ reduced levels of the FcγRIIB mRNA and protein and also decreased the activity of the FcγRIIB p(-729/+585) Luc reporter. Moreover, levels of the FcγRIIB receptor were significantly higher in the Stat1-deficient splenic cells than in the wild-type cells. Accordingly, increased expression of IFN-β in lupus-prone B6.Nba2-ABC mice, as compared with non-lupus-prone C57BL/6 (B6) or B6.Nba2-C mice, was associated with reduced expression of the FcγRIIB receptor. Notably, overexpression of the p202 protein in cells decreased the expression of the Aim2 gene, activated the IFN response, and suppressed the expression of the Fcgr2b gene. These observations demonstrate that the expression of Aim2 protein is required to maintain the expression of the Fcgr2b gene and also predict epistatic interactions between the Ifi200 genes and the Fcgr2b gene within the Nba2 interval.

Recent progress in studies of infantile hemangioma

A hallmark of infantile hemangioma, the most common tumor of infancy, is its dramatic growth after birth, by diffuse proliferation of immature endothelial cells, followed by spontaneous regression. The growth and involution of infantile hemangioma is quite different from other vascular anomalies, which do not regress and can occur at any time during life. Some hemangioma lesions can be extremely disfiguring and destructive to normal tissue and may even be life-threatening. Unfortunately, existing therapeutic approaches have limited success and significant adverse effects of some treatment modalities limit their use. Better understanding of the pathogenesis of hemangioma will enable the development of better therapeutic strategies. Here, we review recent studies and new hypotheses on the pathogenesis of the tumor. Detailed mechanisms of activated vascular endothelial growth factor signaling in tumor cells, identification of their origin and characterization of multipotent stem cells that can give rise to infantile hemangioma are shedding new light on this intriguing vascular tumor.

Functional and clinical consequences of Fc receptor polymorphic and copy number variants

Receptors for immunoglobulins (Fc receptors) play a central role during an immune response, as they mediate the specific recognition of antigens of almost infinite diversity by leucocytes, thereby linking the humoral and cellular components of immunity. Indeed, engagement of Fc receptors by immunoglobulins initiates a range of immunoregulatory processes that might also play a role in disease pathogenesis. In the circulation, five main types of immunoglobulins (Ig) exist - namely IgG, IgA, IgE, IgM and IgD and receptors with the ability to recognize and bind to IgG (Fc gamma receptor family), IgE (Fc epsilon RI and CD23), IgA (CD89; Fc alpha/microR) and IgM (Fc alpha/microR) have been identified and characterized. However, it is astonishing that nearly all the known human Fc receptors display extensive genetic variation with clear implications for their function, thus representing a substantial genetic risk factor for the pathogenesis of a range of chronic inflammatory disorders.

Impaired inhibitory Fcgamma receptor IIB expression on B cells in chronic inflammatory demyelinating polyneuropathy

The inhibitory Fc-gamma receptor FcgammaRIIB, expressed on myeloid and B cells, has a critical role in the balance of tolerance and autoimmunity, and is required for the antiinflammatory activity of intravenous Ig (IVIG) in various murine disease models. However, the function of FcgammaRIIB and its regulation by IVIG in human autoimmune diseases are less well understood. Chronic inflammatory demyelinating polyneuropathy (CIDP) is the most common treatable acquired chronic polyneuropathy, and IVIG is widely used as a first-line initial and maintenance treatment. We found that untreated patients with CIDP, compared with demographically matched healthy controls, showed consistently lower FcgammaRIIB expression levels on naive B cells, and failed to up-regulate or to maintain up-regulation of FcgammaRIIB as B cells progressed from the naive to the memory compartment. Concomitantly, the rare -386C/-120A FcgammaRIIB promoter polymorphism resulting in reduced promoter activity previously associated with autoimmune phenotypes was overrepresented in CIDP. Also, FcgammaRIIB protein expression was up-regulated on monocytes and B cells after clinically effective IVIG therapy. Thus, our results suggest that the inhibitory FcgammaRIIB is impaired at a critical B cell differentiation checkpoint in CIDP, and that modulating FcgammaRIIB expression might be a promising approach to efficiently limit antibody-mediated immunopathology in CIDP.

Do Estrogen Receptor beta Polymorphisms Play A Role in the Pharmacogenetics of Estrogen Signaling?

Estrogen hormones play critical roles in the regulation of many tissue functions. The effects of estrogens are primarily mediated by the estrogen receptors (ER) alpha and beta. ERs are ligand-activated transcription factors that regulate a complex array of genomic events that orchestrate cellular growth, differentiation and death. Although many factors contribute to their etiology, estrogens are thought to be the primary agents for the development and/or progression of target tissue malignancies. Many of the current modalities for the treatment of estrogen target tissue malignancies are based on agents with diverse pharmacology that alter or prevent ER functions by acting as estrogen competitors. Although these compounds have been successfully used in clinical settings, the efficacy of treatment shows variability. An increasing body of evidence implicates ERalpha polymorphisms as one of the contributory factors for differential responses to estrogen competitors. This review aims to highlight the recent findings on polymorphisms of the lately identified ERbeta in order to provide a functional perspective with potential pharmacogenomic implications.

Inhibition of B cell receptor-mediated activation of primary human B cells by coengagement of CD19 and FcgammaRIIb with Fc-engineered antibodies

The humoral immune response requires antigen-specific B cell activation and subsequent terminal differentiation into plasma cells. Engagement of B cell antigen receptor (BCR) on mature B cells activates an intracellular signaling cascade, including calcium mobilization, which leads to cell proliferation and differentiation. Coengagement by immune complex of BCR with the inhibitory Fc receptor FcgammaRIIb, the only IgG receptor expressed on B cells, inhibits B cell activation signals through a negative feedback loop. We now describe antibodies that mimic the inhibitory effects of immune complex by high-affinity coengagement of FcgammaRIIb and the BCR coreceptor complex on human B cells. We engineered the Fc domain of an anti-CD19 antibody to generate variants with up to approximately 430-fold greater affinity to FcgammaRIIb. Relative to native IgG1, the FcgammaRIIb binding-enhanced (IIbE) variants strongly inhibited BCR-induced calcium mobilization and viability in primary human B cells. Inhibitory effects involved phosphorylation of SH2-containing inositol polyphosphate 5-phosphatase (SHIP), which is known to be involved in FcgammaRIIb-induced negative feedback of B cell activation by immune complex. Coengagement of BCR and FcgammaRIIb by IIbE variants also overcame the anti-apoptotic effects of BCR activation. The use of a single antibody to suppress B cell functions by coengagement of BCR and FcgammaRIIb may represent a novel approach in the treatment of B cell-mediated autoimmune diseases.

Transcriptional profiling of murine organ genes in response to infection with Bacillus anthracis Ames spores

Bacillus anthracis is the Gram-positive, spore-forming etiological agent of anthrax, an affliction studied because of its importance as a potential bioweapon. Although in vitro transcriptional responses of macrophages to either spore or anthrax toxins have been previously reported, little is known regarding the impact of infection on gene expression in host tissues. We infected Swiss-Webster mice intranasally with 5 LD(50) of B. anthracis-virulent Ames spores and observed the global transcriptional profiles of various tissues over a 48 h time period. RNA was extracted from spleen, lung, and heart tissues of infected and control mice and examined by Affymetrix GeneChip analysis. Approximately 580 host genes were significantly over or under expressed among the lung, spleen, and heart tissues at 8 and 48 h time points. Expression of genes encoding for surfactant and major histocompatibility complex (MHC) presentation was diminished during the early phase of infection in lungs. By 48 h, a significant number of genes were modulated in the heart, including up-regulation of calcium-binding-related gene expression, and down-regulation of multiple genes related to cell adhesion, formation of the extracellular matrix, and the cell cytoskeleton. Interestingly, the spleen 8h post-infection showed striking increases in the expression of genes that encode hydrolytic enzymes, and these levels remained elevated throughout infection. Further, genes involving antigen presentation and interferon responses were down-regulated in the spleen at 8 h. In late stages of infection, splenic genes related to the inflammatory response were up-regulated. This study is the first to describe the in vivo global transcriptional response of multiple organs during inhalational anthrax. Although numerous genes related to the host immunological response and certain protection mechanisms were up-regulated in these organs, a vast list of genes important for fully developing and maintaining this response were decreased. Additionally, the lung, spleen, and heart showed differential responses to the infection, further validating the demand for a better understanding of anthrax pathogenesis in order to design therapies against novel targets.