Interleukin 21 and its receptor are involved in NK cell expansion and regulation of lymphocyte function

Cytokines are important in the regulation of haematopoiesis and immune responses, and can influence lymphocyte development. Here we have identified a class I cytokine receptor that is selectively expressed in lymphoid tissues and is capable of signal transduction. The full-length receptor was expressed in BaF3 cells, which created a functional assay for ligand detection and cloning. Conditioned media from activated human CD3+ T cells supported proliferation of the assay cell line. We constructed a complementary DNA expression library from activated human CD3+ T cells, and identified a cytokine with a four-helix-bundle structure using functional cloning. This cytokine is most closely related to IL2 and IL15, and has been designated IL21 with the receptor designated IL21 R. In vitro assays suggest that IL21 has a role in the proliferation and maturation of natural killer (NK) cell populations from bone marrow, in the proliferation of mature B-cell populations co-stimulated with anti-CD40, and in the proliferation of T cells co-stimulated with anti-CD3.

Interleukin 20: discovery, receptor identification, and role in epidermal function

A structural, profile-based algorithm was used to identify interleukin 20 (IL-20), a novel IL-10 homolog. Chromosomal localization of IL-20 led to the discovery of an IL-10 family cytokine cluster. Overexpression of IL-20 in transgenic (TG) mice causes neonatal lethality with skin abnormalities including aberrant epidermal differentiation. Recombinant IL-20 protein stimulates a signal transduction pathway through STAT3 in a keratinocyte cell line, demonstrating a direct action of this ligand. An IL-20 receptor was identified as a heterodimer of two orphan class II cytokine receptor subunits. Both receptor subunits are expressed in skin and are dramatically upregulated in psoriatic skin. Taken together, these results demonstrate a role in epidermal function and psoriasis for IL-20, a novel cytokine identified solely by bioinformatics analysis.

A biomaterials approach to peripheral nerve regeneration: bridging the peripheral nerve gap and enhancing functional recovery

Microsurgical techniques for the treatment of large peripheral nerve injuries (such as the gold standard autograft) and its main clinically approved alternative--hollow nerve guidance conduits (NGCs)--have a number of limitations that need to be addressed. NGCs, in particular, are limited to treating a relatively short nerve gap (4 cm in length) and are often associated with poor functional recovery. Recent advances in biomaterials and tissue engineering approaches are seeking to overcome the limitations associated with these treatment methods. This review critically discusses the advances in biomaterial-based NGCs, their limitations and where future improvements may be required. Recent developments include the incorporation of topographical guidance features and/or intraluminal structures, which attempt to guide Schwann cell (SC) migration and axonal regrowth towards their distal targets. The use of such strategies requires consideration of the size and distribution of these topographical features, as well as a suitable surface for cell-material interactions. Likewise, cellular and molecular-based therapies are being considered for the creation of a more conductive nerve microenvironment. For example, hurdles associated with the short half-lives and low stability of molecular therapies are being surmounted through the use of controlled delivery systems. Similarly, cells (SCs, stem cells and genetically modified cells) are being delivered with biomaterial matrices in attempts to control their dispersion and to facilitate their incorporation within the host regeneration process. Despite recent advances in peripheral nerve repair, there are a number of key factors that need to be considered in order for these new technologies to reach the clinic.

Antimicrobial effect of surgical masks coated with nanoparticles

This study assessed the antimicrobial activity of nanoparticles (consisting of a mixture of silver nitrate and titanium dioxide) and nanoparticle-coated facemasks to protect against infectious agents. The minimum inhibitory concentrations of the nanoparticles against Escherichia coli and Staphylococcus aureus were 1/128 and 1/512, respectively. The antibacterial activity of nanoparticle-coated masks was quantified according to the procedures of AATCC 100-1999. A 100% reduction in viable E. coli and S. aureus was observed in the coated mask materials after 48 h of incubation. Skin irritation was not observed in any of the volunteers who wore the facemasks. Nanoparticles show promise when applied as a coating to the surface of protective clothing in reducing the risk of transmission of infectious agents.

The pleckstrin homology domain of Bruton tyrosine kinase interacts with protein kinase C

Bruton tyrosine kinase (EC 2.7.1.112) [Btk, encoded by Btk in mice and BTK in humans (formerly known as atk, BPK, or emb)], which is variously mutated in chromosome X-linked agammaglobulinemia patients and X-linked immunodeficient (xid) mice, has the pleckstrin homology (PH) domain at its amino terminus. The PH domain of Btk expressed as a bacterial fusion protein directly interacts with protein kinase C in mast cell lysates. Evidence was obtained that Btk is physically associated with protein kinase C in intact murine mast cells as well. Both Ca(2+)-dependent (alpha, beta I, and beta II) and Ca(2+)-independent protein kinase C isoforms (epsilon and zeta) in mast cells interact with the PH domain of Btk in vitro, and protein kinase C beta I is associated with Btk in vivo. Btk served as a substrate of protein kinase C, and its enzymatic activity was down-regulated by protein kinase C-mediated phosphorylation. Furthermore, depletion or inhibition of protein kinase C with pharmacological agents resulted in an enhancement of the tyrosine phosphorylation of Btk induced by mast cell activation.

Alteration in left ventricular diastolic filling and accumulation of myocardial collagen at insulin-resistant prediabetic stage of a type II diabetic rat model

BACKGROUND

Considerable controversy exists regarding impairment of cardiac function in diabetes mellitus (DM). We investigated the serial changes in left ventricular (LV) histopathology and LV filling dynamics in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, which have been established as an animal model of type II DM.

METHODS AND RESULTS

In 54 OLETF and 54 non-DM rats, body weight, blood pressure, heart rate, and transmitral pulsed Doppler examinations were performed from 5 to 47 weeks of age. An oral glucose tolerance test was performed at 10, 20, and 30 weeks of age. The hearts were excised for histopathology, including immunohistochemistry and histomorphometry of collagen, and measurement of hydroxyproline at baseline and each stage of developing DM. In the prediabetic stage (15 weeks of age), in which fast blood glucose remained normal, OLETF rats manifested mild obesity, postprandial hyperglycemia, and hyperinsulinemia, and early diastolic transmitral inflow exhibited prolonged deceleration time (OLETF, 59+/-10 ms versus non-DM, 49+/-8 ms, P<0.01) and low peak velocity (OLETF, 73+/-11 cm/s versus non-DM, 88+/-11 cm/s, P<0.01). Histopathology revealed extracellular fibrosis and abundant transforming growth factor-beta(1) receptor II in LV myocytes of OLETF rats. At 15 weeks of age, the ratio of collagen area/visual field of LV wall in OLETF rats (8.3+/-1.3%) was larger than that in non-DM rats (4.9+/-1.8%, P<0.0001), and the collagen content/dry tissue weight ratio of heart was significantly higher in OLETF (2. 0+/-0.5 mg/g) than non-DM (1.3+/-0.2 mg/g, P<0.01) rats.

CONCLUSIONS

A metabolic abnormality present in the prestage of type II DM may produce LV fibrosis and alteration in cardiac function.

Vasostatin, a calreticulin fragment, inhibits angiogenesis and suppresses tumor growth

An endothelial cell inhibitor was purified from supernatant of an Epstein-Barr virus-immortalized cell line and identified as fragments of calreticulin. The purified recombinant NH2-terminal domain of calreticulin (amino acids 1-180) inhibited the proliferation of endothelial cells, but not cells of other lineages, and suppressed angiogenesis in vivo. We have named this NH2-terminal domain of calreticulin vasostatin. When inoculated into athymic mice, vasostatin significantly reduced growth of human Burkitt lymphoma and human colon carcinoma. Compared with other inhibitors of angiogenesis, vasostatin is a small, soluble, and stable molecule that is easy to produce and deliver. As an angiogenesis inhibitor that specifically targets proliferating endothelial cells, vasostatin has a unique potential for cancer treatment.

Anterior cruciate ligament tears: MR imaging compared with arthroscopy and clinical tests

Seventy-nine magnetic resonance (MR) studies of the knee were reviewed in an evaluation of the ability of MR imaging to demonstrate arthroscopically proved anterior cruciate ligament (ACL) tears. MR findings were also compared with the findings of two commonly applied clinical tests of ACL instability: the Lachman test and the anterior drawer test. The sensitivity of MR imaging was 94% (17 of 18), compared with 78% (14 of 18) for the anterior drawer test and 89% (16 of 18) for the Lachman test. The specificity was 100% for all three. Three MR criteria were applied: irregularity or a wavy contour of the anterior margin of the ligament, high-signal-intensity change within the substance of the ligament on T2-weighted images, and discontinuity of that substance. The sagittal T2-weighted image was especially helpful, producing an "arthrographic" effect, in which the anterior margin of the ACL is outlined by high-signal-intensity joint fluid. By demonstrating ACL and other extrameniscal lesions, MR imaging may help clarify the mechanisms of knee injury.

Isoproterenol induction of vasodepressor-type reaction in vasodepressor-prone persons

The ability of isoproterenol to induce symptoms and laboratory findings of a vasodepressor reaction was tested in 48 patients, ages 17 to 74, divided into 4 groups according to the reason for their referral. Group 1 comprised 12 patients with vasodepressor syncope, group 2 had 8 patients with syncope of unknown origin, group 3 included 11 patients with syncope due to seizures in 2 and ventricular tachycardia in 9, group 4 had 17 patients with various arrhythmias not associated with syncope. Isoproterenol boluses were administered starting at 2 micrograms and increased in 2-micrograms steps to a maximum of 8 micrograms at 0 degree and +60 degrees. The responses at 0 degrees were all normal. At +60 degrees a vasodepressor reaction consisting of syncope or near syncope, hypotension and bradycardia was produced by isoproterenol (mean dose 6.0 +/- 0.26 micrograms) in 8 patients from group 1 (66.6%), 4 from group 2 (50%), 0 from group 3 and 4 from group 4 (23.5%). Three of the 4 patients in group 4 had a remote history of classic vasodepressor syncope. The overall sensitivity and specificity of the test were 73 and 85%, respectively, while the predictive accuracy of a test with positive or negative outcome were 69 and 89%, respectively. Muscarinic receptor blockade with atropine in 4 patients prevented isoproterenol-induced bradycardia but not hypotension or symptoms of fainting. Beta-adrenergic receptor blockade with propranolol inhibited all aspects of the isoproterenol-induced faint. Thus, the administration of isoproterenol during a passive upright tilt may identify persons who suffer from or are prone to a vasodepressor reaction.

Involvement of Bruton's tyrosine kinase in FcepsilonRI-dependent mast cell degranulation and cytokine production

We investigated the role of Bruton's tyrosine kinase (Btk) in FcepsilonRI-dependent activation of mouse mast cells, using xid and btk null mutant mice. Unlike B cell development, mast cell development is apparently normal in these btk mutant mice. However, mast cells derived from these mice exhibited significant abnormalities in FcepsilonRI-dependent function. xid mice primed with anti-dinitrophenyl monoclonal IgE antibody exhibited mildly diminished early-phase and severely blunted late-phase anaphylactic reactions in response to antigen challenge in vivo. Consistent with this finding, cultured mast cells derived from the bone marrow cells of xid or btk null mice exhibited mild impairments in degranulation, and more profound defects in the production of several cytokines, upon FcepsilonRI cross-linking. Moreover, the transcriptional activities of these cytokine genes were severely reduced in FcepsilonRI-stimulated btk mutant mast cells. The specificity of these effects of btk mutations was confirmed by the improvement in the ability of btk mutant mast cells to degranulate and to secrete cytokines after the retroviral transfer of wild-type btk cDNA, but not of vector or kinase-dead btk cDNA. Retroviral transfer of Emt (= Itk/Tsk), Btk's closest relative, also partially improved the ability of btk mutant mast cells to secrete mediators. Taken together, these results demonstrate an important role for Btk in the full expression of FcepsilonRI signal transduction in mast cells.

Digoxin metabolism in the elderly

Tritiated digoxin (0.5 mg) was given intravenously to five elderly men (mean age, 77 years) and nine young men (mean age, 27 years). The elderly were not in congestive heart failure. The serum creatinines of the old and young were not different. However, the creatinine clearance averaged 56 ml/min/1.73 m 2 in the old and 122 ml/min/1.73 m 2 in the young ( P <0.001). Digoxin clearance averaged 53 ml/min/1.73 m 2 in the old and 83 ml/min/1.73 m 2 in the young ( P <0.001). The blood concentrations of tritiated digoxin were significantly higher in the elderly throughout the study ( P <0.05). When blood digoxin concentrations were corrected for body surface area, there was no significant difference between the two groups during the first 24 hr, but thereafter the concentrations in the elderly were higher.

The same dose of digoxin resulted in higher blood concentrations and longer blood half-life in the elderly. This is due to the smaller body size and a diminished urinary excretion of digoxin in the elderly.

Interleukin 4 or oncostatin M induces a prolonged increase in P-selectin mRNA and protein in human endothelial cells

During acute inflammation, P-selectin is transiently mobilized from Weibel-Palade bodies to the surface of histamine-activated endothelial cells, where it mediates rolling adhesion of neutrophils under hydrodynamic flow. During chronic or allergic inflammation, sustained expression of P-selectin on the endothelial cell surface has been observed. We found that the cytokines interleukin 4 (IL-4) or oncostatin M (OSM) induced a five- to ninefold increase in P-selectin messenger RNA (mRNA) in human umbilical vein endothelial cells (HUVEC) that persisted as long as 72 h. IL-4 elevated P-selectin mRNA by increasing its transcription rate rather than by prolonging its already long half-life. Stimulation of P-selectin transcription by IL-4 or OSM required new protein synthesis and tyrosine phosphorylation of cellular proteins. Tumor necrosis factor alpha, IL-1 beta, lipopolysaccharide, or IL-3 did not increase P-selectin mRNA in HUVEC, and did not augment the IL-4-induced increase in P-selectin transcripts. IL-4 or OSM increased P-selectin protein on the cell surface as well as in Weibel-Palade bodies. Under flow conditions, neutrophils rolled on P-selectin expressed by IL-4-treated HUVEC, and even more neutrophils rolled on P-selectin after IL-4-treated HUVEC were stimulated with histamine. These data demonstrate that IL-4 or OSM stimulates endothelial cells to synthesize more P-selectin over prolonged periods. The increased expression of P-selectin may facilitate the emigration of leukocytes into sites of chronic or allergic inflammation.

Diagnosis of soft-tissue masses with MR imaging: can benign masses be differentiated from malignant ones?

A blinded, retrospective review of 83 soft-tissue masses (49 benign and 34 malignant) was performed to evaluate the ability to distinguish benign from malignant soft-tissue masses with magnetic resonance (MR) imaging. The correct histologic diagnosis was reached in 31% of cases by one reader and in 16% of cases by the second reader. Mean sensitivity was 50% for benign masses and 80% for malignant masses. The majority of both benign and malignant masses had inhomogeneous signal intensity and at least partially irregular borders. Malignant masses uncommonly had smooth borders and homogeneous signal intensity. MR imaging can be used to evaluate the extent of soft-tissue masses, but most masses will require biopsy to determine if they are benign or malignant.

Phenotypic Drift in Human Tenocyte Culture

Tendon ruptures are increasingly common, repair can be difficult, and healing is poorly understood. Tissue engineering approaches often require expansion of cell numbers to populate a construct, and maintenance of cell phenotype is essential for tissue regeneration. Here, we characterize the phenotype of human Achilles tenocytes and assess how this is affected by passaging. Tenocytes, isolated from tendon samples from 6 patients receiving surgery for rupture of the Achilles tendon, were passaged 8 times. Proliferation rates and cell morphology were recorded at passages 1, 4, and 8. Total collagen, the ratio of collagen types I and III, and decorin were used as indicators of matrix formation, and expression of the integrin beta1 subunit as a marker of cell-matrix interactions. With increasing passage number, cells became more rounded, were more widely spaced at confluence, and confluent cell density declined from 18,700/cm2 to 16,100/cm2 ( p = 0.009). No change to total cell layer collagen was observed but the ratio of type III to type I collagen increased from 0.60 at passage 1 to 0.89 at passage 8 ( p < 0.001). Decorin expression significantly decreased with passage number, from 22.9 +/- 3.1 ng/ng of DNA at passage 1, to 9.1 +/- 1.8 ng/ng of DNA at passage 8 ( p < 0.001). Integrin expression did not change. We conclude that the phenotype of tenocytes in culture rapidly drifts with progressive passage.

Occult intraosseous fracture: detection with MR imaging

Magnetic resonance (MR) images were retrospectively evaluated in eight patients who had recent, symptomatic knee injuries and in whom plain radiographs showed no fractures. T2-weighted images revealed irregular, intraosseous areas of high signal intensity; T1-weighted and proton density images revealed speckled or linear regions of low signal intensity in corresponding areas. In the seven patients whose injuries did not result from direct contusion, abnormalities occurred in subchondral locations. Two patients underwent bone scintigraphy, which showed increased activity in locations corresponding to areas of abnormality noted on MR images. Two patients underwent follow-up MR imaging at 6 weeks and 3 months, which showed complete resolution of the abnormalities. The authors speculate that the MR imaging findings represent microscopic compression fracture of trabecular bone and discuss the related entity, stress fracture.

A soluble class II cytokine receptor, IL-22RA2, is a naturally occurring IL-22 antagonist

IL-22 is an IL-10 homologue that binds to and signals through the class II cytokine receptor heterodimer IL-22RA1/CRF2-4. IL-22 is produced by T cells and induces the production of acute-phase reactants in vitro and in vivo, suggesting its involvement in inflammation. Here we report the identification of a class II cytokine receptor designated IL-22RA2 (IL-22 receptor-alpha 2) that appears to be a naturally expressed soluble receptor. IL-22RA2 shares amino acid sequence homology with IL-22RA1 (also known as IL-22R, zcytor11, and CRF2-9) and is physically adjacent to IL-20Ralpha and IFN-gammaR1 on chromosome 6q23.3-24.2. We demonstrate that IL-22RA2 binds specifically to IL-22 and neutralizes IL-22-induced proliferation of BaF3 cells expressing IL-22 receptor subunits. IL-22RA2 mRNA is highly expressed in placenta and spleen by Northern blotting. PCR analysis using RNA from various tissues and cell lines showed that IL-22RA2 was expressed in a range of tissues, including those in the digestive, female reproductive, and immune systems. In situ hybridization revealed the dominant cell types expressing IL-22RA2 were mononuclear cells and epithelium. Because IL-22 induces the expression of acute phase reactants, IL-22RA2 may play an important role as an IL-22 antagonist in the regulation of inflammatory responses.

Stress fractures: MR imaging

Five cases of stress fracture were studied with high-field-strength magnetic resonance (MR) imaging. In all cases, MR images showed bandlike areas of very low signal intensity in the intramedullary space, which were continuous with the cortex. These findings corresponded in location to the sites of fracture or new bone formation noted on radiographs. Surrounding areas of decreased signal intensity in the marrow space were also consistently seen on T1-weighted images. In three cases, prominent intramedullary areas of high signal intensity were noted on T2-weighted images obtained within 3 weeks of the onset of symptoms. Juxtacortical and/or subperiosteal areas of high signal intensity were also seen on T2-weighted images in two cases. Characteristic MR findings may distinguish stress fracture from occult intraosseous fracture.

Coordinated movement of RACK1 with activated betaIIPKC

Protein kinase C (PKC) isozymes move upon activation from one intracellular site to another. PKC-binding proteins, such as receptors for activated C kinase (RACKs), play an important role in regulating the localization and diverse functions of PKC isozymes. RACK1, the receptor for activated betaIIPKC, determines the localization and functional activity of betaIIPKC. However, the mechanism by which RACK1 localizes activated betaIIPKC is not known. Here, we provide evidence that the intracellular localization of RACK1 changes in response to PKC activation. In Chinese hamster ovary cells transfected with the dopamine D2L receptor and in NG108-15 cells, PKC activation by either phorbol ester or a dopamine D2 receptor agonist caused the movement of RACK1. Moreover, PKC activation resulted in the in situ association and movement of RACK1 and betaIIPKC to the same intracellular sites. Time course studies indicate that PKC activation induces the association of the two proteins prior to their co-movement. We further show that association of RACK1 and betaIIPKC is required for the movement of both proteins. Our results suggest that RACK1 is a PKC shuttling protein that moves betaIIPKC from one intracellular site to another.

Fibroblast growth factor-18 is a trophic factor for mature chondrocytes and their progenitors

OBJECTIVE

The aim of this study was to examine the effects of recombinant human Fgf18 on chondrocyte proliferation and matrix production in vivo and in vitro. In addition, the expressions of Fgf18 and Fgf receptors (Fgfr) in adult human articular cartilage were examined.

METHODS

Adenovirus-mediated transfer of Fgf18 into murine pinnae and addition of FGF18 to primary cultures of adult articular chondrocytes were used to assess the effects of FGF18 on chondrocytes. In situ hybridization was used to examine the expression of Fgf18 and Fgfr s in adult human articular cartilage.

RESULTS

Expression of Fgf18 by adenovirus-mediated gene transfer in murine pinnae resulted in a significant increase in chondrocyte number. Chondrocytes were identified by staining with toluidine blue and a monoclonal antibody directed against type II collagen. Fgf18, Fgfr 2-(IIIc), Fgfr 3-(IIIc), and Fgfr 4 mRNAs were detected within these cells by in situ hybridization. The nuclei of the chondrocytes stained with antibodies to PCNA and FGF receptor (FGFR) 2. Addition of FGF18 to the culture media of primary articular chondrocytes increased the proliferation of these cells and increased their production of extracellular matrix. To assess the receptor selectivity of FGF18, BaF3 cells stably expressing the genes for the major splice variants of Fgfr1-3 were used. Proliferation of cells expressing Fgfr 3-(IIIc) or Fgfr 2-(IIIc) was increased by incubation with FGF18. Using FGFR-Fc fusion proteins and BaF3 cells expressing Fgfr 3-(IIIc), only FGFR 3-(IIIc)-Fc, FGFR 2-(IIIc)-Fc or FGFR 4-Fc reduced FGF18-mediated cell proliferation. Expression of Fgf18, Fgfr 3-(IIIc) and Fgfr 2-(IIIc) mRNAs was localized to chondrocytes of human articular cartilage by in situ hybridization.

CONCLUSION

These data demonstrate that Fgf18 can act as a trophic factor for elastic chondrocytes and their progenitors in vivo and articular chondrocytes cultured in vitro. Expression of Fgf18 and the genes for two of its receptors in chondrocytes suggests that Fgf18 may play an autocrine role in the biology of normal articular cartilage.

BioMart Central Portal: an open database network for the biological community

BioMart Central Portal is a first of its kind, community-driven effort to provide unified access to dozens of biological databases spanning genomics, proteomics, model organisms, cancer data, ontology information and more. Anybody can contribute an independently maintained resource to the Central Portal, allowing it to be exposed to and shared with the research community, and linking it with the other resources in the portal. Users can take advantage of the common interface to quickly utilize different sources without learning a new system for each. The system also simplifies cross-database searches that might otherwise require several complicated steps. Several integrated tools streamline common tasks, such as converting between ID formats and retrieving sequences. The combination of a wide variety of databases, an easy-to-use interface, robust programmatic access and the array of tools make Central Portal a one-stop shop for biological data querying. Here, we describe the structure of Central Portal and show example queries to demonstrate its capabilities.

Association between CYP2D6 *10 genotype and survival of breast cancer patients receiving tamoxifen treatment

BACKGROUND

Human cytochrome P450 2D6 (CYP2D6) genotype may affect the efficacy of tamoxifen treatment in Caucasian women with breast cancer. The most common polymorphism of CYP2D6 in Chinese women is variant 10 (188 C to T).

PATIENTS AND METHODS

Tamoxifen and 4-hydroxytamoxifen (4OHtam) were measured in the serum of 37 women with breast cancer who were receiving tamoxifen treatment. The association between CYP2D6 *10 genotype and survival was determined in a cohort of 293 women with breast cancer who received tamoxifen (n = 152) or who did not (n = 141).

RESULTS

The serum 4OHtam concentrations were significantly lower in women with the CYP2D6 *10 homozygous variant T/T genotype than in those with the homozygous wild-type C/C genotype (P = 0.04). Among tamoxifen-treated women, women with the T/T genotype had a significantly worse disease-free survival (DFS) than those with the C/C or C/T genotype, and the T/T genotype remained an independent prognostic factor of DFS in multivariate analysis (hazard ratio = 4.7; 95% confidence interval = 1.1-20.0; P = 0.04). Among women who did not receive tamoxifen, there was no significant association between CYP2D6 *10 genotype and survival.

CONCLUSION

In tamoxifen-treated patients, women with the CYP2D6 *10 T/T genotype have a lower 4OHtam level in the serum and a worse clinical outcome.

Contribution of the CXC chemokines IP-10 and Mig to the antitumor effects of IL-12

The mechanisms by which interleukin-12 (IL-12) exerts antitumor effects have been difficult to dissect. In this study, we examined the potential contribution of the chemokines interferon-gamma-inducible protein-10 (IP-10) and Mig to the antitumor effects of IL-12. Using an athymic mouse model, local inoculations with IL-12 consistently produced tumor size reductions associated with characteristic tumor necrosis and vascular damage. These effects were indistinguishable from those produced by IP-10 or Mig injected locally in the same tumor model. Local and systemic treatment with IL-12 was associated with expression of the interferon-gamma (IFN-gamma), IP-10, and Mig genes and proteins in the tumor. Levels of IP-10 and Mig expression in the tumor, the liver, and the kidney were inversely correlated with tumor size. Administration in vivo of neutralizing antibodies to IP-10 and Mig reduced substantially the antitumor effects of IL-12 inoculated locally into the tumors. These results support the notion that IP-10 and Mig contribute to the antitumor effects of IL-12 through their inhibitory effects on tumor vasculature.