A new agarose-based microsystem to investigate cell response to prolonged confinement.

Emerging evidence suggests the importance of mechanical stimuli in normal and pathological situations for the control of many critical cellular functions. While the effect of matrix stiffness has been and is still extensively studied, few studies have focused on the role of mechanical stresses. The main limitation of such analyses is the lack of standard in vitro assays enabling extended mechanical stimulation compatible with dynamic biological and biophysical cell characterization. We have developed an agarose-based microsystem, the soft cell confiner, which enables the precise control of confinement for single or mixed cell populations. The rigidity of the confiner matches physiological conditions and its porosity enables passive medium renewal. It is compatible with time-lapse microscopy, in situ immunostaining, and standard molecular analyses, and can be used with both adherent and non-adherent cell lines. Cell proliferation of various cell lines (hematopoietic cells, MCF10A epithelial breast cells and HS27A stromal cells) was followed for several days up to confluence using video-microscopy and further documented by Western blot and immunostaining. Interestingly, even though the nuclear projected area was much larger upon confinement, with many highly deformed nuclei (non-circular shape), cell viability, assessed by live and dead cell staining, was unaffected for up to 8 days in the confiner. However, there was a decrease in cell proliferation upon confinement for all cell lines tested. The soft cell confiner is thus a valuable tool to decipher the effects of long-term confinement and deformation on the biology of cell populations. This tool will be instrumental in deciphering the impact of nuclear and cytoskeletal mechanosensitivity in normal and pathological conditions involving highly confined situations, such as those reported upon aging with fibrosis or during cancer.

Successful transcatheter pulmonary valve implantation in a dog: first clinical report.

Transcatheter pulmonary valve (TPV) implantation is a therapeutic approach approved by the United States Food and Drug Administration for human patients with failing pulmonary conduits in 2010 and for failing bioprosthetic surgical pulmonary valves in 2017. We report here the first successful transcatheter implantation of a stented valve in a pulmonary position in a dog with congenital pulmonary valve disease. A 3-year-old, 10.9 kg, client-owned Beagle dog was referred for a follow-up visit after a percutaneous balloon valvuloplasty performed 22 months before for treatment of a severe type A valvular pulmonary stenosis. The Doppler-derived peak pressure gradient was 348 mmHg before the procedure and 66 mmHg 24 h after. The dog was lethargic. Echocardiography revealed a mild pulmonary stenosis (pressure gradient-43 mmHg), severe pulmonary regurgitation, and secondary severe right ventricular and right atrial dilation. Worsening of right heart dilation was observed 2 months later despite medical therapy. A TPV implantation was performed using a prestented Melody bovine jugular bioprosthetic valve. The dog recovered uneventfully and was discharged 10 days after the procedure. Right heart dilation resolved within 15 days. The dog was doing well 7 months after valve implantation. This case demonstrates that TPV implantation with a stented valve is technically feasible in dogs with severe pulmonary valve disease. Stringent postoperative care, with particular attention to thrombosis and infectious endocarditis, and appropriate sizing and positioning of the valve stent are keys to the success of this procedure.

CXCR4 inhibitors could benefit to HER2 but not to triple-negative breast cancer patients.

The CXCR4 receptor and its ligand CXCL12 (also named stromal cell-derived factor 1, SDF1) have a critical role in chemotaxis and homing, key steps in cancer metastasis. Although myofibroblasts expressing CXCL12 are associated with the presence of axillary metastases in HER2 breast cancers (BC), the therapeutic interest of targeting CXCR4/CXCL12 axis in the different BC subtypes remains unclear. Here, we investigate this question by testing antitumor activity of CXCR4 inhibitors in patient-derived xenografts (PDX), which faithfully reproduce human tumor properties. We observed that two CXCR4 inhibitors, AMD3100 and TN14003, efficiently impair tumor growth and metastasis dissemination in both Herceptin-sensitive and Herceptin-resistant HER2 BC. Conversely, blocking CXCR4/CXCL12 pathway in triple-negative (TN) BC does not reduce tumor growth, and can even increase metastatic spread. Moreover, although CXCR4 inhibitors significantly reduce myofibroblast content in all BC subtypes, they decrease angiogenesis only in HER2 BC. Thus, our findings suggest that targeting CXCR4 could provide some therapeutic interest for HER2 BC patients, whereas it has no impact or could even be detrimental for TN BC patients.

Vigilance in industry: cosmetics and household cleaning products. Balance sheet of case report from 2005 to 2007.

BACKGROUND: Unlike medicinal products, cosmetics are not subject to marketing authorization in France. Nevertheless, the Agence Francaise de Sécurité Sanitaire des Produits de Santé (AFSSAPS; French Agency for the Safety of Healthcare Products) has been working on the development of a cosmetovigilance system for several years, with the aim of establishing standard procedures for collecting adverse reactions to cosmetics from the manufacturers. AIM: To assess the incidence of skin reactions to cosmetics or household products. Unilever established its own 'vigilance' standard system in France in late 2003. This report describes the experience acquired from 2005 to 2007. METHODS: Case reports were collected in compliance with a standard procedure. The cases were then analysed by the consultant dermatologist in accordance with a pharmacovigilance-based method (chronological criteria, clinical criteria, possible rechallenge test, patch tests). RESULTS: During the period 2005 to 2007, a total of 102,689 consumers contacted the consumer department, including 842 (0.82%) who reported skin reactions. After analysis of the collected data, 0.144 skin reaction cases per million units sold were found to be attributable to cosmetic or household products. CONCLUSIONS: The implementation of a structured vigilance system in the cosmetics and household products industry is an efficient tool for manufacturers, both for information purposes and for product improvement, as well as meeting the transparency requirements of health authorities and consumers.

Increased tumorigenicity of cells carrying recombinant human herpesvirus 8.

Human herpesvirus 8 (HHV-8) infection is associated with the development of Kaposi's sarcoma and primary effusion lymphoma. The cloning of the HHV-8 genome into a bacterial artificial chromosome (BAC) allows researchers to mutate and identify the relative importance of HHV-8 genes essential for growth and replication in tissue culture systems. However, in vivo models to study the impact of such mutations are very limited. Consequently, the objective of this study was to determine whether cells carrying the HHV-8 BAC would form tumors when injected into mice, enabling the use of this model to assess the influence of viral gene mutation on tumorigenesis. To do so, 293T and 293T-E1 cells carrying recombinant HHV-8 were injected into SCID mice and tumor growth was analyzed. Our results clearly show that mice injected with 293T-E1 cells had a significantly higher tumor incidence level as well as increased tumor volumes and weights compared to mice injected with 293T control cells. Cells carrying the HHV-8 genome grew faster and more aggressively in SCID mice than control 293T cells, highlighting the oncogenic properties of HHV-8. The model presented could therefore be used for the identification of HHV-8 genes contributing to tumorigenesis in the context of the entire viral genome.

Clinical course of premature infants intubated in the delivery room, submitted or not to porcine-derived lung surfactant therapy within the first hour of life.

OBJECTIVES: The aim of this study was to perform a comparative analysis of the clinical outcome, gasometric course and ventilatory indices of premature infants with a gestational age of < or = 34 weeks who were intubated in the delivery room, owing to respiratory insufficiency, according to whether or not they were submitted to porcine-derived lung surfactant therapy within the first hour of life. METHODS: The study was randomized and controlled. A total of 75 premature infants were classified into two groups: group A, comprising 35 neonates who were submitted to surfactant within the first hour of life; and group B, comprising 40 neonates who were not submitted to surfactant within the first hour of life. RESULTS: Exogenous surfactant therapy after establishment of respiratory distress syndrome (RDS) was necessary in eight neonates of group A (22.9%) and 31 neonates of group B (77.5%) (p < 0.001). The neonates in group A presented higher levels in relation to group B for the variables: partial pressure of arterial oxygen (PaO2)/fraction of inspired oxygen (FiO2) and PaO2/partial pressure of alveolar oxygen (PAO2), while neonates in group B presented higher levels for FiO2, PAO2 and difference D(A - a)O2 in relation to group A. Weight affected the oxygenation index (OI) parameter, in that neonates with lower weight presented greater values of the OI. CONCLUSIONS: In premature infants with established RDS, the need for exogenous surfactant was lower in the group that received surfactant within the first hour of life. Furthermore, the gasometric parameters and ventilatory indexes presented a better course in the first 24 h of life among premature infants who received exogenous surfactant within the first hour of life, in relation to those who did not.

A test of Braden's Self-Help Model in adults with chronic pain.

PURPOSE: To test hypothesized relationships in Braden's Self-Help Model in a sample of people with idiopathic chronic pain. Testing theoretical explanations and predictions with various clinical populations under different sociocultural, economic, climatic, and health system environments provides evidence about the applicability of the underlying theory among diverse populations. DESIGN: This study was part of a larger randomized, controlled trial of a community-based nursing psycho-educational intervention: the Chronic Pain Self-Management Program (CPSMP). Pretest and posttest data were collected in 1995-1996 in Newfoundland, Canada. METHODS: Participants completed a battery of valid and reliable self-report instruments to measure pain, disability, uncertainty, resourcefulness, self-efficacy, adult role behaviors, and life satisfaction. Two tests of the self-help model were performed, the first with pretest data (N = 110) and the second with 3-month posttest data (N = 102) after half the sample had participated in the CPSMP intervention. Causal modeling path analysis was done with the Statistical Package for the Social Sciences (SPSS) program and tests of goodness-of-fit were conducted using EQS for Windows. RESULTS: Results supported the overall hypothesized pattern of relationships in the self-help model. Amounts of variance explained in the two major outcomes of the model (self-help: 42% to 53% and life quality: 45% to 47%) were consistent with results from other studies. Indices of goodness of fit showed an adequate fit of the model to the data, particularly the posttest data. CONCLUSIONS: Braden's Self-Help Model appears to be robust in a variety of clinical populations, among different settings and environmental conditions, and provides a useful framework to guide nursing psycho-educational interventions in chronic illness.

Soluble CD14 acts as a negative regulator of human T cell activation and function.

T cell activation is controlled by the coordination of stimulatory and negative regulatory signals which are not completely defined. In this study we tested for a possible direct effect of CD14 on the regulation of T cell activation and function. We show that soluble CD14 (sCD14) induces inhibition of antigen-mediated peripheral blood mononuclear cells (PBMC) proliferation and anti-CD3-mediated proliferation of CD4+CD8+, CD4+CD8+ and CD4+CD8+ Tcell clones. This effect is not due to cell death, but results from a marked inhibition of IL-2 production. Proliferation of T cell clones due to exogenous IL-2 is not affected by sCD14. We also found that sCD14 inhibits production of another Th1-like cytokine, IFN-gamma and a Th2-like cytokine, IL-4. Importantly, sCD14 induces a progressive accumulation of the inhibitory protein IkappaB-alpha. We show that sCD14 binds to activated T cells. Following cell activation, biotinylated sCD14 stains CD3+ PBMC, as well as human T cell clones with varying intensity. The binding is saturable, can be inhibited by excess of unlabeled sCD14 and, following binding, sCD14 is internalized. Collectively, these findings reveal a previously unrecognized function of sCD14, namely its capacity to negatively regulate T lymphocyte activation and function by interacting directly with activated T cells.

Randomized controlled trial of a community-based psychoeducation program for the self-management of chronic pain.

Although chronic pain is a frequent cause of suffering and disability and is costly to society, there continues to be limited access to specialty pain clinic services. Hence, there is a need for cost-effective, accessible interventions that will help people find ways to better manage this difficult problem. This randomized controlled trial examined the effect of a low-cost, community-based, nurse-delivered, group psychoeducation program entitled the Chronic Pain Self-Management Program (CPSMP). It has a standard protocol that was modified from the successful Arthritis Self-Management Program (ASMP). One hundred and ten individuals with mixed idiopathic chronic pain conditions were enrolled in the study (75% female; mean age 40 years; mean chronicity 6 years) and were randomly assigned to one of two conditions: the 12-h (CPSMP) intervention group, or the 3-month wait-list control group. Self-report measures of pain-related and other quality of life variables as well as two hypothesized mediating variables were collected pre-treatment and 3 months later by assessors blind to group allocation. One hundred and two subjects completed the study. Results of intention-to-treat analysis indicated that the treatment group made significant short-term improvements in pain, dependency, vitality, aspects of role functioning, life satisfaction and in self-efficacy and resourcefulness as compared to the wait-list control group. Because it has a standard protocol, this intervention has the potential to be reliably delivered at low cost in varied urban and rural community settings and hence be more widely accessible to a greater number of people suffering from chronic pain than is currently the case with more specialized pain clinic services. Based on the results of this study, further research evaluating the long-term impact and potential cost savings to the individual and to the health care system is warranted.

Predictors of the development of chronic pain.

The purpose of this secondary analysis was to explore the role of potential risk factors in predicting the development of chronic pain. Linear discriminant function analysis was used to derive a prediction equation that maximized the differences between a group of hospitalized patients experiencing acute pain who developed chronic pain (n = 171) and a group whose pain resolved (n = 200). Patients who developed chronic pain reported a higher pain intensity, higher anxiety and distress, less certainty that their pain would resolve, longer hospitalization, less independence in ambulation, a diagnosis of trauma, and less need for surgery. Recognition of these factors could lead to early identification of those individuals with acute pain who are at risk for developing chronic pain.

Detection and biochemical characteristics of the receptor for complexes of soluble CD14 and bacterial lipopolysaccharide.

Soluble CD14 (sCD14) has been found to bind LPS and mediate LPS activation of several cell types. It has been postulated that sCD14-LPS complexes induce cell responses by interacting with a cell surface structure, which, in turn, triggers cell activation. There has been no biochemical evidence, however, for a direct interaction of sCD14 with a cell surface structure, and the putative receptor has not been identified. To rigorously test this hypothesis, we studied the interaction of human rsCD14 with cells in the absence of serum and in the presence and the absence of LPS. We found 1) there was specific and saturable binding of 125I-sCD14, indicative of a typical receptor-ligand interaction, to several cell types, including endothelial cells, epithelial cells, astrocytes, and human monocytes; 2) specific binding to all the cell types and IL-6 induction in membrane-bound CD14 (mCD14)-negative cells occurred only when both sCD14 and LPS were present; 3) competitive displacement experiments of 125I-sCD14 binding to astrocytes and Scatchard plots revealed a binding of high affinity (Kd = 3.3 +/- 0.4 nM) and approximately 25,000 single class binding sites/cell; 4) the steady state for the association of 125I-sCD14 was obtained after 180-200 min; 5) chemical cross-linking experiments revealed the association of sCD14 with a binding structure of approximately 216 kDa; 6) binding of 125I-sCD14 to CD14-expressing cell transfectants was about 50% lower than that to nontransfected cells. Maximal binding, however, was recovered after removing mCD14, suggesting that the sCD14-LPS receptor may also interact with mCD14. These results provide direct biochemical evidence for the existence of a cell surface signal-mediating binding structure for LPS-bearing sCD14 and suggest that this structure may represent the signaling unit of the postulated multimeric LPS receptor in mCD14-bearing cells.

A case report of Down syndrome and centroblastic lymphoma.

We describe a case of left cervical stage I centroblastic lymphoma in a 29-year old male patient with Down's syndrome due to a (14; 21) Robertsonian translocation. The disease presented as extensive lymph node necrosis leaving rare areas of tumor cells, accounting for the diagnostic difficulties. According to our review of the literature, lymphoma is one of the most common neoplasms in DS patients and may represent the second most common malignancy in this condition, far behind leukemia.

Cloning and characterization of a specific interleukin (IL)-13 binding protein structurally related to the IL-5 receptor alpha chain.

Interleukin-13 (IL-13) is a cytokine secreted by activated T lymphocytes that shares many, but not all, biological activities with IL-4. These overlapping activities are probably due to the existence of common receptor components. Two proteins have been described as constituents of the IL-4 receptor, a approximately 140-kDa glycoprotein (IL-4R) and the gamma chain (gammac) of the IL-2 receptor, but neither of these proteins binds IL-13. We have cloned a cDNA encoding an IL-13 binding protein (IL-13R) from the Caki-1 human renal carcinoma cell line. The cloned cDNA encodes a 380-amino acid protein with two consensus patterns characteristic of the hematopoietic cytokine receptor family and a short cytoplasmic tail. The IL-13R shows homology with the IL-5 receptor, and to a lesser extent, with the prolactin receptor. COS-7 cells transfected with the IL-13R cDNA bind IL-13 with high affinity but do not bind IL-4. COS-7 cells co-transfected with the cloned IL-13R cDNA and IL-4R cDNA resulted in the reconstitution of a small number of receptors that recognized both IL-4 and IL-13. Reverse transcription-polymerase chain reaction analysis detected the receptor transcript only in cell lines known to bind IL-13.

[Fibrinolysis of deep venous thrombosis on implantable perfusion devices. Apropos of a consecutive series of 57 cases of thrombosis and 32 cases of fibrinolysis]. / Fibrinolyse des thromboses veineuses profondes sur dispositifs de perfusion implantables. A propos d'une série consécutive de 57 thromboses et de 32 fibrinolyses.

The main complication of totally implantable venous access devices is deep venous thrombosis on catheter. It may dramatically reduce the already limited venous capacity of patients undergoing chemotherapy and obturate catheters, causing pulmonary embolism or functional disorders. These thromboses usually involve veins of the superior vena cava system where the catheters are implanted. Generally, they occur early, are extensive and often asymptomatic. Doppler ultrasonography is the diagnostic investigation of choice, phlebography being reserved for particular cases or to specify the limits of the thrombus. In a series of 412 vein access devices implanted and systematically monitored by Doppler ultrasonography, we found 57 thromboses (13.8%), 15 partial and 42 complete. The lowest thrombosis rate was observed in the right internal jugular vein (10% vs 20 to 23%, p = 0.006). Thirty-two patients received a systemic fibrinolytic treatment, 16 with streptokinase (SK), five with urokinase (UK), four with tissue plasminogen activator (rt-PA) and seven with SK/UK association. No serious side effects were observed. Sixteen repermeabilizations (50% of fibrinolysis) were obtained. There were no significant differences with respect to the fibrinolytic, the initial characteristics of thrombosis or the patients. Patients without fibrinolysis received 3 weeks of low molecular weight heparin (curative doses) then warfarin. Only one patient was repermeabilized with this treatment (significative difference with fibrinolysis: p = 0.009). Fibrinolysis is indicated in symptomatic thrombosis and/or in cases of extension to the innominate vein or the superior vena cava. Systematic monitoring by Doppler ultrasonography and prophylactic anti-thrombotic treatment are recommended in patients with implantable venous access devices in order to decrease the occurrence of thromboses, to detect asymptomatic patients at an early stage and to increase the effectiveness of fibrinolysis.

IL-13 and IL-4 share signal transduction elements as well as receptor components in TF-1 cells.

IL-13 and IL-4 are growth factors for the human erythroleukemia cell line TF-1. In these cells both cytokines share overlapping binding sites, but the number of sites for IL-13 is half of that for IL-4. Two monoclonal antibodies against the extracellular domain of the IL-4R alpha chain completely abolish the binding of IL-13, although IL-13 does not bind to this chain. Following receptor triggering, IL-13 and IL-4 induce the phosphorylation of a 170 kDa protein, probably the IL-4-induced phosphotyrosine substrate. In addition the phosphorylation of the 170 kDa protein results in its tight association with phosphatidylinositol-3-kinase.

Characterization and comparison of the interleukin 13 receptor with the interleukin 4 receptor on several cell types.

We describe here the characterization of the interleukin (IL) 13 receptor and a comparison with the IL-4 receptor on different cell types. Several, but not all, of the IL-4 receptor-positive cells showed specific IL-13 binding, which was always completely displaced by IL-4. In the IL-13 receptor-positive cells, the IL-13 either completely or partially displaced the labeled IL-4. Further characterization of the IL-13 receptor in two cell lines, COS-3 and A431, representative of the groups of complete and partial displacement of IL-4 by IL-13, respectively, showed that the IL-13 binds with high affinity (Kd approximately 300 pM) to both cells and that the number of binding sites is, in COS-3 cells, equivalent to that for IL-4 and, in A431 cells, is smaller than that for IL-4. Cross-linking of labeled IL-13 yielded, on COS-3 cells, two affinity-labeled complexes of 220 and 70 kDa, and on A431 cells, one complex of 70 kDa; labeled IL-4 yielded on both cells the same pattern of three complexes of 220, 145, and 70 kDa. Altogether, these results suggest that the IL-13 receptor may be constituted by a subset of the IL-4 receptor complex associated with at least one additional protein.

Return to work following an aquafitness and muscle strengthening program for the low back injured.

Our purpose, in this prospective clinical study, was to identify the best predictors of 2-month return to work or retraining for a group of low back injured subjects (n = 40) who completed at least 8 weeks of a community-based rehabilitation program that combined aerobic and flexibility exercise conducted in the water (aquafitness) with muscle strength and endurance training. Baseline demographic characteristics and changes in physical fitness, pain, disability, and psychological well-being during the course of program participation were compared between two groups of low back injured subjects: those who returned to work (RTW) [n = 24], and those who did not (N-RTW) [n = 16]. Subjects in both groups showed comparable improvement in measures of physical fitness at 8 weeks. However, multivariate analyses showed significant between-group differences in self-report measures. The RTW group showed significant improvement in measures of pain, disability, anxiety, and vigor while self-esteem and affect remained stable. The N-RTW group displayed no change in pain and disability variables and had significant deterioration in mean overall psychological well-being over time. The best predictors of return to work using logistic regression analyses were a first injury rather than a repeat injury to the lower back, and stability in self-esteem. Suggestions are offered for further research to examine the benefits of aquafit exercise for the low back injured, for additional interventions for those with a reinjury, and for maintaining or enhancing self-esteem as a treatment goal.

Interleukin-6 regulation of CCK/gastrin receptors and amylase secretion in a rat pancreatic acinar cell line (AR4-2J).

In necrotizing pancreatitis a high interleukin-6 (IL-6) serum level has been proposed as a prognostic criterium. However, literature does not report any information about the role of IL-6 in the function of pancreatic acinar cells. Cholecystokinin, gastrin binding, amylase release and intracellular calcium measurement were performed on a rat pancreatoma cell line, AR4-2J, which has been recognized as a useful tool for studies on the long-term regulation of pancreatic acinar cells. The addition of IL-6 (400 pM) for 48hrs to the AR4-2J cells induced no change in the binding affinities but there was a 2 fold increase in the binding capacity of cholecytokinin (CCKA R) and gastrin (CCKB R) receptors. Although IL-6 treatment did not change directly the secretory capacity and did not activate the intracellular calcium mobilization of AR4-2J, it indirectly increased the sensitivity of the cells to the stimulation of amylase release and the intracellular calcium mobilization by cholecystokinin and gastrin. It is most likely this effect was due to the IL-6-induced increase in the numbers of CCKA R and CCKB R. Therefore this report suggests that the cytokine IL-6 acts on the CCK regulation of pancreatic enzyme secretion.

Primary structure and functional expression of mouse pituitary and human brain corticotrophin releasing factor receptors.

Corticotrophin-releasing factor (CRF) is the principal hypothalamic factor governing the pituitary-adrenal axis, but the wide extra-pituitary distribution of CRF and its receptors suggest a major role for this neuropeptide in the integration of the overall physiological and behavioral responses of an organism to stress. We have cloned a CRF receptor complementary DNA (cDNA) by expression in COS-7 cells of a cDNA library from the AtT20 mouse pituitary tumour cell line. The cloned mouse cDNA was then as a probe to isolate a human CRF receptor cDNA from a human brain cDNA library. The mouse and human cDNAs both encode 415 amino acid proteins that are 97% identical, containing seven putative transmembrane domains characteristic of G protein-coupled receptors. The CRF receptor shows homology with the receptors for growth hormone-releasing factor, vasoactive intestinal peptide, secretin, parathyroid hormone, and calcitonin. COS-7 cells transfected with the mouse CRF receptor cDNA bind radiolabelled ovine CRF with high affinity and respond specifically to CRF by accumulation of intracellular cAMP. A 2.7 kb mRNA coding for the CRF receptor could be detected in AtT20 cells and human cortex tissue. PCR analysis also detected the receptor transcript in human pituitary, brainstem, and testis.

Functional linkage of the Gro beta and IL-8 receptors on the surface of human neutrophils.

Gro beta and IL-8 are two pro-inflammatory cytokines with chemotactic activities on neutrophils. Binding studies were performed to ascertain whether their similar biological activities are mediated through the same receptor. Since Gro beta lacks tyrosine residues, recombinant Gro beta containing an additional carboxyterminal tyrosine residue (Gro beta-Tyr) was produced in transfected COS cells, purified to homogeneity and radiolabelled with 125INa. Saturation experiments using [125I]-Gro beta-Tyr allowed us to identify high affinity receptors on human neutrophils (Kd: 2 +/- 0.5 nM and Bmax: 4760 +/- 761 sites/cell). Experiments using [125I]-IL-8 as ligand, showed no significative differences in affinity (Kd: 4 +/- 0.9 nM) but about two times the number of sites (11316 +/- 1810 sites/cell). In competition experiments using [125I]-Gro beta-Tyr, unlabelled IL-8 and Gro beta-Tyr generated superposable displacement curves (IC50: 0.69 +/- 0.15 nM and 0.42 +/- 0.11 nM, respectively). Interesting, IL-8 binding sites could be down-regulated by Gro beta and IL-8, indicating that the two binding sites may be associated. Cross-linking experiments using [125I]-IL-8 revealed two major bands at 70 and 140 kDa, whereas experiments with [125I]-Gro beta-Tyr showed only the 70 kDa band. Taken together, these results suggest that the human neutrophil IL-8/Gro beta receptor is a dimeric complex with two high affinity binding sites for IL-8 and of those two, only one is shared by Gro beta.