The tumor necrosis factor (TNF) superfamily of cytokines includes both soluble and membrane-bound proteins that regulate immune responses. A member of the human TNF family, BLyS (B lymphocyte stimulator), was identified that induced B cell proliferation and immunoglobulin secretion. BLyS expression on human monocytes could be up-regulated by interferon-gamma. Soluble BLyS functioned as a potent B cell growth factor in costimulation assays. Administration of soluble recombinant BLyS to mice disrupted splenic B and T cell zones and resulted in elevated serum immunoglobulin concentrations. The B cell tropism of BLyS is consistent with its receptor expression on B-lineage cells. The biological profile of BLyS suggests it is involved in monocyte-driven B cell activation.

DR3 is a death domain-containing receptor that is upregulated during T cell activation and whose overexpression induces apoptosis and NF-kappaB activation in cell lines. Here we show that an endothelial cell-derived TNF-like factor, TL1A, is a ligand for DR3 and decoy receptor TR6/DcR3 and that its expression is inducible by TNF and IL-1alpha. TL1A induces NF-kappaB activation and apoptosis in DR3-expressing cell lines, while TR6-Fc protein antagonizes these signaling events. Interestingly, in T cells, TL1A acts as a costimulator that increases IL-2 responsiveness and secretion of proinflammatory cytokines both in vitro and in vivo. Our data suggest that interaction of TL1A with DR3 promotes T cell expansion during an immune response, whereas TR6 has an opposing effect.

IntroductionThe tumor necrosis factor (TNF) family of ligands encompasses an ever-growing group of proteins, characterized by homologous cysteine-rich domains, that participates in the regulation of diverse immune and inflammatory responses. [1][2][3][4] All the members, with the exception of lymphotoxin-␣, are type II membrane proteins. Their effects are mediated either by cell contact, through the interaction of the membrane-bound form of the ligand with its corresponding receptor, or by processing and shedding of the soluble form of the ligand. 2,[5][6][7] In addition, many of the proteins, including CD27L, CD30L, OX40L, CD40L, FasL, and 4-1BBL, have moderate-sized cytoplasmic regions that are capable of delivering signals when engaged by their receptors. [7][8][9][10] The expression pattern of the family members is usually promiscuous, ranging from the broad cellular expression of TNF-␣ to a more restricted localization, such as that of CD40L expressed only on T cells. Moreover, the expression of the molecules is, in general, dependent on the activation state of the cells, being usually low or undetectable on resting cells.Recently, we described a novel member of the TNF family of ligands, B-lymphocyte stimulator (BLyS), which was identified by searching an expressed sequence tag (EST) database for homology with known TNF-like molecules. 11 The protein has been reported also as TALL-1 (TNF-and ApoL-related leukocyte-expressed ligand 1), BAFF (B-cell activator factor belonging to the TNF family), or THANK (TNF homologue that activates apoptosis, NF-B, and JNK). 12-14 The human BLyS gene encodes for a 285 amino acid (aa) protein presenting a transmembrane region between aa 47 and 73 and lacking a putative signal peptide sequence. The recombinant soluble protein (aa 134-285) binds selectively to human primary B cells and tumor cell lines of the B lineage. 11BLyS was shown to induce B-cell proliferation in standard costimulation assays with Staphylococcus aureus Cowan I (SAC I) or antihuman immunoglobulin M (IgM). BLyS administration in mice resulted in a 5-and 2-fold increase in serum IgM and IgA, respectively. 11 In addition, mice transgenic for BAFF developed autoimmune disorders such as increased germinal center formation, production of autoantibodies, and Ig deposition in kidneys. 15 Collectively, these findings suggest that BLyS has a crucial role in the humoral immune response and that regulation of BLyS expression might consequently modulate B-cell function. Our aim was, therefore, to study synthesis and release of BLyS from cells of myeloid lineage and to investigate the regulation of BLyS expression in response to cytokines. Materials and methods Medium and reagentsThe complete medium used for monocyte culture consisted of RPMI 1640 medium (Gibco BRL, Rockville, MD) supplemented with 10% (vol/vol) heat-inactivated fetal bovine serum (FBS), 2 M L-glutamine, and 50 g/mL gentamycin (Biofluids, Rockville, MD). The following recombinant human (rh) reagents were used: interferon-␥ (rhIFN-␥), interleukin-10 (...

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis in a variety of tumour cells through activation of TRAIL-R1 and TRAIL-R2 death signalling receptors. Here, we describe the characterisation and activity of HGS-ETR1, the first fully human, agonistic TRAIL-R1 mAb that is being developed as an antitumour therapeutic agent. HGS-ETR1 showed specific binding to TRAIL-R1 receptor. HGS-ETR1 reduced the viability of multiple types of tumour cells in vitro, and induced activation of caspase 8, Bid, caspase 9, caspase 3, and cleavage of PARP, indicating activation of TRAIL-R1 alone was sufficient to induce both extrinsic and intrinsic apoptotic pathways. Treatment of cell lines in vitro with HGS-ETR1 enhanced the cytotoxicity of chemotherapeutic agents (camptothecin, cisplatin, carboplatin, or 5-fluorouracil) even in tumour cell lines that were not sensitive to HGS-ETR1 alone. In vivo administration of HGS-ETR1 resulted in rapid tumour regression or repression of tumour growth in pre-established colon, non-smallcell lung, and renal tumours in xenograft models. Combination of HGS-ETR1 with chemotherapeutic agents (topotecan, 5-fluorouracil, and irinotecan) in three independent colon cancer xenograft models resulted in an enhanced antitumour efficacy compared to either agent alone. Pharmacokinetic studies in the mouse following intravenous injection showed that HGS-ETR1 serum concentrations were biphasic with a terminal half-life of 6.9 -8.7 days and a steady-state volume of distribution of approximately 60 ml kg À1 . Clearance was 3.6 -5.7 ml À1 day À1 kg À1 . These data suggest that HGS-ETR1 is a specific and potent antitumour agent with favourable pharmacokinetic characteristics and the potential to provide therapeutic benefit for a broad range of human malignancies.

As part of a large scale effort to discover novel secreted proteins, a cDNA encoding a novel cytokine was identified. Alignments of the sequence of the new protein, designated IL-17B, suggest it to be a homolog of the recently described T cell-derived cytokine, IL-17. By Northern analysis, EST distribution and real-time quantitative polymerase chain reaction analysis, mRNA was detected in many cell types. A novel type I transmembrane protein, identified in an EST data base by homology to IL-17R, was found to bind specifically IL-17B, as determined by surface plasmon resonance analysis, flow cytometry, and co-immunoprecipitation experiments. Readily detectable transcription of IL-17BR was restricted to human kidney, pancreas, liver, brain, and intestines and only a few of the many cell lines tested. By using a rodent ortholog of IL-17BR as a probe, IL-17BR message was found to be drastically up-regulated during intestinal inflammation elicited by indomethacin treatment in rats. In addition, intraperitoneal injection of IL-17B purified from Chinese hamster ovary cells caused marked neutrophil migration in normal mice, in a specific and dose-dependent manner. Together these results suggest that IL-17B may be a novel proinflammatory cytokine acting on a restricted set of target cell types. They also demonstrate the strength of genomic approaches in the unraveling of novel biological pathways.