Activation-induced tumor necrosis factor receptor-associated factor 3 (Traf3) alternative splicing controls the noncanonical nuclear factor κB pathway and chemokine expression in human T cells

Get Spliced: Uniting Alternative Splicing and Arthritis

Immune responses demand the rapid and precise regulation of gene protein expression. Splicing is a crucial step in this process; ~95% of protein-coding gene transcripts are spliced during mRNA maturation. Alternative splicing allows for distinct functional regulation, as it can affect transcript degradation and can lead to alternative functional protein isoforms. There is increasing evidence that splicing can directly regulate immune responses. For several genes, immune cells display dramatic changes in isoform-level transcript expression patterns upon activation. Recent advances in long-read RNA sequencing assays have enabled an unbiased and complete description of transcript isoform expression patterns. With an increasing amount of cell types and conditions that have been analyzed with such assays, thousands of novel transcript isoforms have been identified. Alternative splicing has been associated with autoimmune diseases, including arthritis. Here, GWASs revealed that SNPs associated with arthritis are enriched in splice sites. In this review, we will discuss how alternative splicing is involved in immune responses and how the dysregulation of alternative splicing can contribute to arthritis pathogenesis. In addition, we will discuss the therapeutic potential of modulating alternative splicing, which includes examples of spliceform-based biomarkers for disease severity or disease subtype, splicing manipulation using antisense oligonucleotides, and the targeting of specific immune-related spliceforms using antibodies.

Alternative Splicing of RIOK3 Engages the Noncanonical NFκB Pathway during Rift Valley Fever Virus Infection

Although the noncanonical NFκB pathway was originally identified as a cellular pathway contributing to lymphoid organogenesis, in the past 20 years, its involvement in innate immunity has become more appreciated. In particular, the noncanonical NFκB pathway has been found to be activated and even exploited by some RNA viruses during infection. Intriguingly, activation of this pathway has been shown to have a role in disrupting transcription of type 1 interferon (IFN), suggesting a rationale for why this response could be co-opted by some viruses. Rift Valley fever virus (RVFV) is a trisegmented ambisense RNA virus that poses a considerable threat to domestic livestock and human health. Previously, we showed the atypical kinase RIOK3 is important for mounting an IFN response to RVFV infection of human epithelial cells, and shortly following infection with RVFV (MP12 strain), RIOK3 mRNA is alternatively spliced to its X2 isoform that encodes a truncated RIOK3 protein. Alternative splicing of RIOK3 mRNA has an inhibitory effect on the IFN response but also stimulates an NFκB-mediated inflammatory response. Here, we demonstrate alternative splicing of RIOK3 mRNA is associated with activation of the noncanonical NFκB pathway and suggest this pathway is co-opted by RVFV (MP12) to enhance viral success during infection.

In silico analysis of alternative splicing events implicated in intracellular trafficking during B-lymphocyte differentiation

There are multiple regulatory layers that control intracellular trafficking and protein secretion, ranging from transcriptional to posttranslational mechanisms. Finely regulated trafficking and secretion is especially important for lymphocytes during activation and differentiation, as the quantity of secretory cargo increases once the activated cells start to produce and secrete large amounts of cytokines, cytotoxins, or antibodies. However, how the secretory machinery dynamically adapts its efficiency and specificity in general and specifically in lymphocytes remains incompletely understood. Here we present a systematic bioinformatics analysis to address RNA-based mechanisms that control intracellular trafficking and protein secretion during B-lymphocyte activation, and differentiation, with a focus on alternative splicing. Our in silico analyses suggest that alternative splicing has a substantial impact on the dynamic adaptation of intracellular traffic and protein secretion in different B cell subtypes, pointing to another regulatory layer to the control of lymphocyte function during activation and differentiation. Furthermore, we suggest that NERF/ELF2 controls the expression of some COPII-related genes in a cell type-specific manner. In addition, T cells and B cells appear to use different adaptive strategies to adjust their secretory machineries during the generation of effector and memory cells, with antibody secreting B cell specifically increasing the expression of components of the early secretory pathway. Together, our data provide hypotheses how cell type-specific regulation of the trafficking machinery during immune cell activation and differentiation is controlled that can now be tested in wet lab experiments.

Role of Alternative Splicing in Regulating Host Response to Viral Infection

The importance of transcriptional regulation of host genes in innate immunity against viral infection has been widely recognized. More recently, post-transcriptional regulatory mechanisms have gained appreciation as an additional and important layer of regulation to fine-tune host immune responses. Here, we review the functional significance of alternative splicing in innate immune responses to viral infection. We describe how several central components of the Type I and III interferon pathways encode spliced isoforms to regulate IFN activation and function. Additionally, the functional roles of splicing factors and modulators in antiviral immunity are discussed. Lastly, we discuss how cell death pathways are regulated by alternative splicing as well as the potential role of this regulation on host immunity and viral infection. Altogether, these studies highlight the importance of RNA splicing in regulating host-virus interactions and suggest a role in downregulating antiviral innate immunity; this may be critical to prevent pathological inflammation.

Hypoxic colorectal cancer-derived extracellular vesicles deliver microRNA-361-3p to facilitate cell proliferation by targeting TRAF3 via the noncanonical NF-κB pathways

BACKGROUND

Hypoxic tumour microenvironment (TME) is a key regulator in cancer progression. However, the communications between hypoxic cells and other components in TME during colorectal cancer (CRC) progression via extracellular vesicles (EVs) remain unclear.

METHODS

High-throughput sequencing was employed to detect aberrantly expressed microRNAs (miRNAs) in hypoxic EVs. Quantitative real-time PCR was used to confirm and screen preliminarily candidate miRNAs. The effects of EVs derived from hypoxia (<1% O2 ) and miR-361-3p on CRC growth were assessed using CCK-8 assays, colony formation assays, EdU assays, flow cytometric assays and mouse xenograft. Then, the specific mechanisms of miR-361-3p were investigated by RNA immunoprecipitation, luciferase reporter assay, Western blot, chromatin immunoprecipitation, immunohistochemistry and rescue experiments.

RESULTS

The level of miR-361-3p expression was remarkably elevated in hypoxic EVs and can be transferred to CRC cells. Functional experiments exhibited that hypoxic EVs facilitated cell growth and suppressed cell apoptosis by transferring miR-361-3p of CRC. Hypoxia-inducible factor-1α induced the elevation of miR-361-3p levels in hypoxic EVs. Upregulated miR-361-3p in CRC inhibited cell apoptosis and facilitated cell growth by directly targeting TNF receptor-associated factor 3, which consequently activated the noncanonical NF-κB pathway. Moreover, the high expression of circulating exosomal miR-361-3p was correlated to worse prognosis of CRC patients.

CONCLUSIONS

Altogether, the abnormality of exosomal miR-361-3p derived from hypoxia acts vital roles in the regulation of CRC growth and apoptosis and can be an emerging prognostic biomarker and a therapeutic target for CRC patients.

A Nonsense N -Terminus NFKB2 Mutation Leading to Haploinsufficiency in a Patient with a Predominantly Antibody Deficiency

The noncanonical NF-κB pathway is implicated in diverse biological and immunological processes. Monoallelic C-terminus loss-of-function and gain-of-function mutations of NFKB2 have been recently identified as a cause of immunodeficiency manifesting with common variable immunodeficiency (CVID) or combined immunodeficiency (CID) phenotypes. Herein we report a family carrying a heterozygous nonsense mutation in NFKB2 (c.809G > A, p.W270*). This variant is associated with increased mRNA decay and no mutant NFKB2 protein expression, leading to NFKB2 haploinsufficiency. Our findings demonstrate that bona fide NFKB2 haploinsufficiency, likely caused by mutant mRNA decay and protein instability leading to the transcription and expression of only the wild-type allele, is associated with clinical immunodeficiency, although with incomplete clinical penetrance. Abnormal B cell development, hypogammaglobulinemia, poor antibody response, and abnormal noncanonical (but normal canonical) NF-κB pathway signaling are the immunologic hallmarks of this disease. This adds a third allelic variant to the pathophysiology of NFKB2-mediated immunodeficiency disorders.

Metabonomic-Transcriptome Integration Analysis on Osteoarthritis and Rheumatoid Arthritis

Purpose

This study is aimed at exploring the potential metabolite/gene biomarkers, as well as the differences between the molecular mechanisms, of osteoarthritis (OA) and rheumatoid arthritis (RA).

Methods

Transcriptome dataset GSE100786 was downloaded to explore the differentially expressed genes (DEGs) between OA samples and RA samples. Meanwhile, metabolomic dataset MTBLS564 was downloaded and preprocessed to obtain metabolites. Then, the principal component analysis (PCA) and linear models were used to reveal DEG-metabolite relations. Finally, metabolic pathway enrichment analysis was performed to investigate the differences between the molecular mechanisms of OA and RA.

Results

A total of 976 DEGs and 171 metabolites were explored between OA samples and RA samples. The PCA and linear module analysis investigated 186 DEG-metabolite interactions including Glycogenin 1- (GYG1-) asparagine_54, hedgehog acyltransferase- (HHAT-) glucose_70, and TNF receptor-associated factor 3- (TRAF3-) acetoacetate_35. Finally, the KEGG pathway analysis showed that these metabolites were mainly enriched in pathways like gap junction, phagosome, NF-kappa B, and IL-17 pathway.

Conclusions

Genes such as HHAT, GYG1, and TRAF3, as well as metabolites including glucose, asparagine, and acetoacetate, might be implicated in the pathogenesis of OA and RA. Metabolites like ethanol and tyrosine might participate differentially in OA and RA progression via the gap junction pathway and phagosome pathway, respectively. TRAF3-acetoacetate interaction may be involved in regulating inflammation in OA and RA by the NF-kappa B and IL-17 pathway.

NFKB2 regulates human Tfh and Tfr pool formation and germinal center potential

Mutations affecting the non-canonical pathway of NF-κB were recently identified to underlie a form of common variable immunodeficiency strongly associated with autoimmunity. Although intrinsic B-cell abnormalities explain most of the humoral defects of this disease, detailed data on the impact of NFKB2 on follicular helper (Tfh) and regulatory (Tregs) T cells are scarce. Here, we show that Tfh, CXCR5⁺, and CXCR5^- Treg cell subsets were significantly reduced in patients heterozygous for a truncating mutation of NFKB2. Plasma CXCL13 levels were reduced, underlining an important role for NFKB2 in regulating the germinal center (GC) response. Proinflammatory IFNγ, IL-17 and IL-10 cytokine production by CD4 T cells was lower in the mutated patients, but the production of IL-4 and IL-21 was not altered. Taken together, our findings show that NFKB2 influences the quality and efficiency of human GC reaction, by affecting not only the B cells but also GC-relevant T cell subsets.

Differential Interleukin-2 Transcription Kinetics Render Mouse but Not Human T Cells Vulnerable to Splicing Inhibition Early after Activation

T cells are nodal players in the adaptive immune response against pathogens and malignant cells. Alternative splicing plays a crucial role in T cell activation, which is analyzed mainly at later time points upon stimulation. Here we have discovered a 2-h time window early after stimulation where optimal splicing efficiency or, more generally, gene expression efficiency is crucial for successful T cell activation. Reducing the splicing efficiency at 4 to 6 h poststimulation significantly impaired murine T cell activation, which was dependent on the expression dynamics of the Egr1-Nab2-interleukin-2 (IL-2) pathway. This time window overlaps the time of peak IL-2 de novo transcription, which, we suggest, represents a permissive time window in which decreased splicing (or transcription) efficiency reduces mature IL-2 production, thereby hampering murine T cell activation. Notably, the distinct expression kinetics of the Egr1-Nab2-IL-2 pathway between mouse and human render human T cells refractory to this vulnerability. We propose that the rational temporal modulation of splicing or transcription during peak de novo expression of key effectors can be used to fine-tune stimulation-dependent biological outcomes. Our data also show that critical consideration is required when extrapolating mouse data to the human system in basic and translational research.

A Perspective Review on the Role of Nanomedicine in the Modulation of TNF-TNFR2 Axis in Breast Cancer Immunotherapy

In the past decade, nanomedicine research has provided us with highly useful agents (nanoparticles) delivering therapeutic drugs to target cancer cells. The present review highlights nanomedicine applications for breast cancer immunotherapy. Recent studies have suggested that tumour necrosis factor (TNF) and its receptor 2 (TNFR2) expressed on breast cancer cells have important functional consequences. This cytokine/receptor interaction is also critical for promoting highly immune-suppressive phenotypes by regulatory T cells (Tregs). This review generally provides a background for nanoparticles as potential drug delivery agents for immunomodulators and further discusses in depth the potential of TNF antagonists delivery to modulate TNF-TNFR2 interactions and inhibit breast cancer progression.

Genome-wide identification of alternative splicing events that regulate protein transport across the secretory pathway

Alternative splicing (AS) strongly increases proteome diversity and functionality in eukaryotic cells. Protein secretion is a tightly-controlled process, especially in a tissue-specific and differentiation-dependent manner. While previous work has focussed on transcriptional and post-translational regulatory mechanisms, the impact of AS on the secretory pathway remains largely unexplored. Here we integrate a published screen for modulators of protein transport and RNA-Seq analyses to identify over 200 AS events as secretion regulators. We confirm that splicing events along all stages of the secretory pathway regulate the efficiency of membrane trafficking using Morpholinos and CRISPR/Cas9. We furthermore show that these events are highly tissue-specific and adapt the secretory pathway during T-cell activation and adipocyte differentiation. Our data substantially advance the understanding of AS functionality, add a new regulatory layer to a fundamental cell biological process and provide a resource of alternative isoforms that control the secretory pathway.

Role of TRAFs in Signaling Pathways Controlling T Follicular Helper Cell Differentiation and T Cell-Dependent Antibody Responses

Follicular helper T (T_FH) cells represent a highly specialized CD4⁺ T cell subpopulation that supports the generation of germinal centers (GC) and provides B cells with critical signals promoting antibody class switching, generation of high affinity antibodies, and memory formation. T_FH cells are characterized by the expression of the chemokine receptor CXCR5, the transcription factor Bcl-6, costimulatory molecules ICOS, and PD-1, and the production of cytokine IL-21. The acquisition of a T_FH phenotype is a complex and multistep process that involves signals received through engagement of the TCR along with a multitude of costimulatory molecules and cytokines receptors. Members of the Tumor necrosis factor Receptor Associated Factors (TRAF) represent one of the major classes of signaling mediators involved in the differentiation and functions of T_FH cells. TRAF molecules are the canonical adaptor molecules that physically interact with members of the Tumor Necrosis Factor Receptor Superfamily (TNFRSF) and actively modulate their downstream signaling cascades through their adaptor function and/or E3 ubiquitin ligase activity. OX-40, GITR, and 4-1BB are the TRAF-dependent TNFRSF members that have been implicated in the differentiation and functions of T_FH cells. On the other hand, emerging data demonstrate that TRAF proteins also participate in signaling from the TCR and CD28, which deliver critical signals leading to the differentiation of T_FH cells. More intriguingly, we recently showed that the cytoplasmic tail of ICOS contains a conserved TANK-binding kinase 1 (TBK1)-binding motif that is shared with TBK1-binding TRAF proteins. The presence of this TRAF-mimicking signaling module downstream of ICOS is required to mediate the maturation step during T_FH differentiation. In addition, JAK-STAT pathways emanating from IL-2, IL-6, IL-21, and IL-27 cytokine receptors affect T_FH development, and crosstalk between TRAF-mediated pathways and the JAK-STAT pathways can contribute to generate integrated signals required to drive and sustain T_FH differentiation. In this review, we will introduce the molecular interactions and the major signaling pathways controlling the differentiation of T_FH cells. In each case, we will highlight the contributions of TRAF proteins to these signaling pathways. Finally, we will discuss the role of individual TRAF proteins in the regulation of T cell-dependent humoral responses.

Negative Regulation of Interferon-β Production by Alternative Splicing of Tumor Necrosis Factor Receptor-Associated Factor 3 in Ducks

Tumor necrosis factor receptor-associated factor 3 (TRAF3), an intracellular signal transducer, is identified as an important component of Toll-like receptors and RIG-I-like receptors induced type I interferon (IFN) signaling pathways. Previous studies have clarified TRAF3 function in mammals, but little is known about the role of TRAF3 in ducks. Here, we cloned and characterized the full-length duck TRAF3 (duTRAF3) gene and an alternatively spliced isoform of duTRAF3 (duTRAF3-S) lacking the fragment encoding amino acids 217–319, from duck embryo fibroblasts (DEFs). We found that duTRAF3 and duTRAF3-S played different roles in regulating IFN-β production in DEFs. duTRAF3 through its TRAF domain interacted with duMAVS or duTRIF, leading to the production of IFN-β. However, duTRAF3-S, containing the TRAF domain, was unable to bind duMAVS or duTRIF due to the intramolecular binding between the N- and C-terminal of duTRAF3-S that blocked the function of its TRAF domain. Further analysis identified that duTRAF3-S competed with duTRAF3 itself for binding to duTRAF3, perturbing duTRAF3 self-association, which impaired the assembly of duTRAF3-duMAVS/duTRIF complex, ultimately resulted in a reduced production of IFN-β. These findings suggest that duTRAF3 is an important regulator of duck innate immune signaling and reveal a novel mechanism for the negative regulation of IFN-β production via changing the formation of the homo-oligomerization of wild molecules, implying a novel regulatory role of truncated proteins.

Novel nonsense gain-of-function NFKB2 mutations associated with a combined immunodeficiency phenotype

NF-κB signaling through its NFKB1-dependent canonical and NFKB2-dependent noncanonical pathways plays distinctive roles in a diverse range of immune processes. Recently, mutations in these 2 genes have been associated with common variable immunodeficiency (CVID). While studying patients with genetically uncharacterized primary immunodeficiencies, we detected 2 novel nonsense gain-of-function (GOF) NFKB2 mutations (E418X and R635X) in 3 patients from 2 families, and a novel missense change (S866R) in another patient. Their immunophenotype was assessed by flow cytometry and protein expression; activation of canonical and noncanonical pathways was examined in peripheral blood mononuclear cells and transfected HEK293T cells through immunoblotting, immunohistochemistry, luciferase activity, real-time polymerase chain reaction, and multiplex assays. The S866R change disrupted a C-terminal NF-κΒ2 critical site affecting protein phosphorylation and nuclear translocation, resulting in CVID with adrenocorticotropic hormone deficiency, growth hormone deficiency, and mild ectodermal dysplasia as previously described. In contrast, the nonsense mutations E418X and R635X observed in 3 patients led to constitutive nuclear localization and activation of both canonical and noncanonical NF-κΒ pathways, resulting in a combined immunodeficiency (CID) without endocrine or ectodermal manifestations. These changes were also found in 2 asymptomatic relatives. Thus, these novel NFKB2 GOF mutations produce a nonfully penetrant CID phenotype through a different pathophysiologic mechanism than previously described for mutations in NFKB2.

Activation-Dependent TRAF3 Exon 8 Alternative Splicing Is Controlled by CELF2 and hnRNP C Binding to an Upstream Intronic Element

Cell-type-specific and inducible alternative splicing has a fundamental impact on regulating gene expression and cellular function in a variety of settings, including activation and differentiation. We have recently shown that activation-induced skipping of TRAF3 exon 8 activates noncanonical NF-κB signaling upon T cell stimulation, but the regulatory basis for this splicing event remains unknown. Here we identify cis- and trans-regulatory elements rendering this splicing switch activation dependent and cell type specific. The cis-acting element is located 340 to 440 nucleotides upstream of the regulated exon and acts in a distance-dependent manner, since altering the location reduces its activity. A small interfering RNA screen, followed by cross-link immunoprecipitation and mutational analyses, identified CELF2 and hnRNP C as trans-acting factors that directly bind the regulatory sequence and together mediate increased exon skipping in activated T cells. CELF2 expression levels correlate with TRAF3 exon skipping in several model systems, suggesting that CELF2 is the decisive factor, with hnRNP C being necessary but not sufficient. These data suggest an interplay between CELF2 and hnRNP C as the mechanistic basis for activation-dependent alternative splicing of TRAF3 exon 8 and additional exons and uncover an intronic splicing silencer whose full activity depends on the precise location more than 300 nucleotides upstream of the regulated exon.

TRAF3 as a powerful and multitalented regulator of lymphocyte functions

This review summarizes the current state of knowledge regarding the roles of the signaling adapter protein tumor necrosis factor receptor (TNFR)-associated factor 3 in regulating the functions of B and T lymphocytes. In B lymphocytes, TNFR-associated factor 3 inhibits signaling by TNFR superfamily receptors, Toll-like receptors, and interleukin-6R. In contrast, signaling to B cells by the virally encoded oncogenic protein latent membrane protein 1 is promoted by TNFR-associated factor 3. An important B cell-specific role for TNFR-associated factor 3 is the inhibition of homeostatic survival, directly relevant to the common occurrence of TNFR-associated factor 3 mutations in human B cell malignancies. TNFR-associated factor 3 was recently found to be a resident nuclear protein in B cells, where it interacts with and inhibits gene expression mediated by the cAMP response element-binding protein transcription complex, including expression of the prosurvival protein myeloid leukemia cell differentiation protein 1. In T lymphocytes, TNFR-associated factor 3 is required for normal signaling by the T cell antigen receptor, while inhibiting signaling by the interleukin-2 receptor. Cytoplasmic TNFR -associated factor 3 restrains nuclear factor-κB2 activation in both T and B cells. Clinical implications and future directions for the study of this context-dependent signaling regulator are discussed.

Sec16 alternative splicing dynamically controls COPII transport efficiency

The transport of secretory proteins from the endoplasmic reticulum (ER) to the Golgi depends on COPII-coated vesicles. While the basic principles of the COPII machinery have been identified, it remains largely unknown how COPII transport is regulated to accommodate tissue- or activation-specific differences in cargo load and identity. Here we show that activation-induced alternative splicing of Sec16 controls adaptation of COPII transport to increased secretory cargo upon T-cell activation. Using splice-site blocking morpholinos and CRISPR/Cas9-mediated genome engineering, we show that the number of ER exit sites, COPII dynamics and transport efficiency depend on Sec16 alternative splicing. As the mechanistic basis, we suggest the C-terminal Sec16 domain to be a splicing-controlled protein interaction platform, with individual isoforms showing differential abilities to recruit COPII components. Our work connects the COPII pathway with alternative splicing, adding a new regulatory layer to protein secretion and its adaptation to changing cellular environments.

The transport of secretory proteins from the endoplasmic reticulum to the Golgi depends on COPII-coated vesicles. Here, the authors show that activation-induced alternative splicing of Sec16 controls adaptation of COPII transport to increased secretory cargo upon T cell activation.

Roles of TRAF3 in T cells: many surprises

Tumor necrosis factor receptor (TNFR)-associated factor 3 (TRAF3) is broadly involved in different receptor-mediated signaling pathways. Considerable progress was made recently in understanding the role of TRAF3 in T cell biology. Here we review these new findings about how TRAF3 participates in T cell development and function. The different roles of TRAF3 in distinct immune cells are also compared. That TRAF3 is required for T cell effector functions, and invariant Natural Killer T cell function and development, was unexpected. Another surprising finding is that TRAF3 normally restrains regulatory T cell development. It is now clear that TRAF3 regulates signaling to T cells not only through costimulatory members of the TNFR superfamily, but also through the T cell receptor complex, and cytokine receptors. The diverse roles it plays support the multifaceted nature of this molecule. How TRAF3 mediates integration of different signaling cascades is an important topic for future study.

Targeting signaling factors for degradation, an emerging mechanism for TRAF functions

Tumor necrosis factor receptor (TNFR)-associated factors (TRAFs) form a family of proteins that are best known as signaling adapters of TNFRs. However, emerging evidence suggests that TRAF proteins, particularly TRAF2 and TRAF3, also regulate signal transduction by controlling the fate of intracellular signaling factors. A well-recognized function of TRAF2 and TRAF3 in this aspect is to mediate ubiquitin-dependent degradation of nuclear factor-κB (NF-κB)-inducing kinase (NIK), an action required for the control of NIK-regulated non-canonical NF-κB signaling pathway. TRAF2 and TRAF3 form a complex with the E3 ubiquitin ligase cIAP (cIAP1 or cIAP2), in which TRAF3 serves as the NIK-binding adapter. Recent evidence suggests that the cIAP-TRAF2-TRAF3 E3 complex also targets additional signaling factors for ubiquitin-dependent degradation, thereby regulating important aspects of immune and inflammatory responses. This review provides both historical aspects and new insights into the signaling functions of this ubiquitination system.

TNF and TNF-receptors: From mediators of cell death and inflammation to therapeutic giants - past, present and future

Tumor Necrosis Factor (TNF), initially known for its tumor cytotoxicity, is a potent mediator of inflammation, as well as many normal physiological functions in homeostasis and health, and anti-microbial immunity. It also appears to have a central role in neurobiology, although this area of TNF biology is only recently emerging. Here, we review the basic biology of TNF and its normal effector functions, and discuss the advantages and disadvantages of therapeutic neutralization of TNF - now a commonplace practice in the treatment of a wide range of human inflammatory diseases. With over ten years of experience, and an emerging range of anti-TNF biologics now available, we also review their modes of action, which appear to be far more complex than had originally been anticipated. Finally, we highlight the current challenges for therapeutic intervention of TNF: (i) to discover and produce orally delivered small molecule TNF-inhibitors, (ii) to specifically target selected TNF producing cells or individual (diseased) tissue targets, and (iii) to pre-identify anti-TNF treatment responders. Although the future looks bright, the therapeutic modulation of TNF now moves into the era of personalized medicine with society's challenging expectations of durable treatment success and of achieving long-term disease remission.