Interleukin-10 inhibits activation of coagulation and fibrinolysis during human endotoxemia

Interleukin-10 (IL-10) has been found to inhibit lipopolysaccharide (LPS)-induced tissue factor expression by monocytes in vitro. To determine the effects of IL-10 on LPS-induced activation of the hemostatic mechanisms in vivo, we performed a placebo-controlled, cross-over study of human endotoxemia. Two groups of eight volunteers were challenged with LPS (4 ng/kg) on two occasions: once in conjunction with placebo, and once with recombinant human IL-10 (rhIL-10; 25 microg/kg). In group 1, placebo or rhIL-10 was given 2 minutes before LPS challenge, group 2 received placebo or rhIL-10 1 hour after LPS administration. Pretreatment with rhIL-10 reduced both LPS-induced activation of the fibrinolytic system (plasma concentrations of tissue type plasminogen activator, plasmin-alpha2-antiplasmin complexes, and D-dimer), and inhibition of fibrinolysis (plasma levels of plasminogen activator inhibitor 1), whereas posttreatment only inhibited the latter response. Both IL-10 pre- and posttreatment attenuated activation of the coagulation system (plasma levels of prothrombin fragment F1 + 2 and thrombin-antithrombin complexes). These results indicate that rhIL-10, besides its well-described inhibitory effects on cytokine release, potently modulates the fibrinolytic system and inhibits the coagulant responses during endotoxemia.     

Systemic hemodynamic and microvascular responses in spontaneously hypertensive rats during Escherichia coli bacteremia

Renovascular hypertension profoundly alters skeletal muscle arteriolar responses to sepsis, yet systemic hemodynamics to sepsis are not affected by hypertension. In this study, we hypothesized that microvascular responses of skeletal muscle and systemic hemodynamics are changed during high- and low-cardiac-output Escherichia coli bacteremia in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). During high-cardiac-output bacteremia, blood pressure and heart rate increased in WKY, but blood pressure decreased in SHR. During low-cardiac-output bacteremia, blood pressure initially decreased in WKY, while in SHR, pressure dropped significantly and remained severely depressed. Heart rate increased by 50% in SHR, but only by 10-15% in WKY during low-cardiac-output bacteremia. Large A1 and A2 arterioles constricted in both WKY and SHR during both phases of bacteremia. Small A3 and A4 arterioles dilated in WKY during bacteremia, but this small arteriole dilation was blunted in SHR. However, nitroprusside, an endothelium-derived relaxing factor (EDRF)-independently acting vasodilator, caused maximal dilation of these small arterioles of SHR. We conclude that there are profound changes and differences in systemic hemodynamics during bacteremia between the normotensive and the genetically hypertensive groups, whereas despite a possibly decreased endothelium-dependent vasodilator responsiveness in small arterioles of SHR during bacteremia, overall blood flow changes in skeletal muscle were similar among the two groups.     

Interleukin-10 controls interferon-gamma and tumor necrosis factor production during experimental endotoxemia

Interleukin-10 (IL-10) is a potent inhibitor of lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF) production and has been shown to protect mice from endotoxin shock. As IFN-gamma is another important mediator of LPS toxicity, we studied the effects of IL-10 on LPS-induced IFN-gamma synthesis in vitro and in vivo. First, we found that the addition of recombinant human IL-10 (rhIL-10) (10 U/ml) to human whole blood markedly suppressed LPS-induced IFN-gamma release while neutralization of endogenously synthesized IL-10 resulted in increased IFN-gamma levels. The ability of rIL-10 to inhibit LPS-induced IFN-gamma synthesis was also observed in vivo in mice. Indeed, administration of 1000 U recombinant mouse IL-10 (rmIL-10) 30 min before and 3 h after challenge of BALB/c mice with 100 micrograms LPS resulted in a threefold decrease in peak IFN-gamma serum levels. We then examined the production and the role of IL-10 during murine endotoxemia. We found that LPS injection causes the rapid release of IL-10, peak IL-10 serum levels being observed 90 min after LPS challenge. Neutralization of endogenously produced IL-10 by administration of 2 mg JES5-2A5 anti-IL-10 monoclonal antibody (mAb) 2 h before LPS challenge resulted in a marked increase in both TNF and IFN-gamma serum levels while irrelevant isotype-matched mAb had no effect. The enhanced production of inflammatory cytokines in anti-IL-10 mAb-treated mice was associated with a 60% lethality after injection of 500 micrograms LPS, while all mice pretreated with control mAb survived. We conclude that the rapid release of IL-10 during endotoxemia is a natural antiinflammatory response controlling cytokine production and LPS toxicity.     

Epinephrine inhibits tumor necrosis factor-alpha and potentiates interleukin 10 production during human endotoxemia

Short-term preexposure of mononuclear cells to epinephrine inhibits LPS-induced production of TNF, whereas preexposure for 24 h results in increased TNF production. To assess the effects of epinephrine infusions of varying duration on in vivo responses to LPS, the following experiments were performed: (a) Blood obtained from eight subjects at 4-24 h after the start of a 24-h infusion of epinephrine (30 ng/kg per min) produced less TNF after ex vivo stimulation with LPS compared with blood drawn before the start of the infusion, and (b) 17 healthy men who were receiving a continuous infusion of epinephrine (30 ng/kg per min) started either 3 h (EPI-3; n = 5) or 24 h (EPI-24; n = 6) were studied after intravenous injection of LPS (2 ng/kg, lot EC-5). EPI-3 inhibited LPS-induced in vivo TNF appearance and also increased IL-10 release (both P < 0.005 versus LPS), whereas EPI-24 only attenuated TNF secretion (P = 0.05). In separate in vitro experiments in whole blood, epinephrine increased LPS-induced IL-10 release by a combined effect on alpha and beta adrenergic receptors. Further, in LPS-stimulated blood, the increase on IL-10 levels caused by epinephrine only marginally contributed to concurrent inhibition of TNF production. Epinephrine, either endogenously produced or administered as a component of sepsis treatment, may have a net antiinflammatory effect on the cytokine network early in the course of systemic infection.     

Capillaries, caveolae, calcium and cyclic nucleotides: a new look at microvascular permeability

Over the past 35 years much effort has been directed at identifying the pathways through microvascular endothelium and unravelling the interactions between the convective and diffusive forces which drive fluid and solutes through them. While increases in permeability induced by inflammatory mediators are known to result from the formation of gaps in venular endothelium, it is only recent advances in cell biology that have allowed the mechanisms regulating permeability to be investigated from a sound base. Results from the general biology of vesicular transport have been applied in studies on the caveolae of microvascular endothelium. Work on single perfused microvessels and on endothelial cell cultures have revealed the importance of intracellular Ca2+ and both cAMP and cGMP in regulating permeability. Even the belief that permeability is increased by gaps developing between the cells has been challenged. Although the mechanisms regulating permeability remain far from clear, sensible hypotheses can now be proposed and tested.     

Monocyte-endothelial cell interactions in vitro, with reference to the influence of interleukin-1 and tumor necrosis factor

This review discusses augmentation strategies for patients with obsessive-compulsive disorder who fail to respond to treatment. A patient's failure to respond to treatment may be due to any of a number of factors, such as noncompliance with a behavioral program, concurrent severe depression or personality disorder, certain ritualistic behaviors, inaccurate diagnosis, and inadequate treatment. It is particularly important that comorbid psychiatric disorders be diagnosed and treated. A review of the literature and my experience with the use of augmenting agents such as lithium, buspirone, clonidine, fenfluramine, antidepressants, anxiolytic agents, and neuroleptics in treatment-resistant obsessive-compulsive disorder are presented. Existing evidence suggests that some of these approaches are useful for some patients. However, many questions remain, and much research remains to be done on this topic.     

Synergistic augmentative effect of interleukin-10 and CD27/CD70 interactions on B-cell immunoglobulin synthesis

BACKGROUND: Patients who complain of constipation can be divided into those who have lost the natural call to stool, but develop abdominal discomfort after several days without a bowel movement (no urge); and those who experience a constant sensation of incomplete evacuation (urge). AIMS: To determine whether the two groups differ in symptoms, colonic transit, and perceptual responses to controlled rectal distension. METHODS: Forty four patients with constipation were evaluated with a bowel symptom questionnaire, colonic transit (radiopaque markers), and rectal balloon distension. Stool (S) and discomfort (D) thresholds to slow ramp (40 ml/min) and rapid phasic distension (870 ml/min) were determined with an electronic distension device. Fifteen healthy controls were also studied. RESULTS: All patients had Rome positive irritable bowel syndrome (IBS); 17 were no urge and 27 urge. Mean D threshold to phasic rectal distensions was 28 (3) mm Hg in no urge, 27 (3) mm Hg in urge (NS), but higher in the control group (46 (2) mm Hg; p < 0.01). Sixty seven per cent of no urge and 69% of urge were hypersensitive for D. Slow ramp distension thresholds were higher in no urge (S: 26 (3); D: 45 (4) mm Hg) compared with urge (S: 16 (2); D: 31 (3) mm Hg; p < 0.01), or with controls (S: 15 (1); D: 30 (3); p < 0.01). CONCLUSIONS: Hyposensitivity to slow rectal distension is found in patients with IBS who complain of constipation and have lost the call to stool even though their sensitivity to phasic distension is increased.     

rZIP, a RING-leucine zipper protein that regulates cell fate determination during Dictyostelium development

Catabolite repression of Bacillus subtilis catabolic operons is supposed to occur via a negative regulatory mechanism involving the recognition of a cis-acting catabolite-responsive element (cre) by a complex of CcpA, which is a member of the GalR-Lacl family of bacterial regulatory proteins, and the seryl-phosphorylated form of HPr (P-ser-HPr), as verified by recent studies on catabolite repression of the gnt operon. Analysis of the gnt promoter region by deletions and point mutations revealed that in addition to the cre in the first gene (gntR) of the gnt operon (credown), this operon contains another cre located in the promoter region (creup). A translational gntR'-'lacZ fusion expressed under the control of various combinations of wild-type and mutant credown and creup was integrated into the chromosomal amyE locus, and then catabolite repression of beta-galactosidase synthesis in the resultant integrants was examined. The in vivo results implied that catabolite repression exerted by creup was probably independent of catabolite repression exerted by credown; both creup and credown catabolite repression involved CcpA. Catabolite repression exerted by creup was independent of P-ser-HPr, and catabolite repression exerted by credown was partially independent of P-ser-HPr. DNase I footprinting experiments indicated that a complex of CcpA and P-ser-HPr did not recognize creup, in contrast to its specific recognition of credown. However, CcpA complexed with glucose-6-phosphate specifically recognized creup as well as credown, but the physiological significance of this complexing is unknown.     

Interleukin-10, interferon gamma, interleukin-2, and soluble interleukin-2 receptor alpha detected during peritonitis in the dialysate and serum of patients on continuous ambulatory peritoneal dialysis

OBJECTIVE: To analyze interleukin (IL)-10, interferon gamma (IFN-gamma), IL-2, and soluble IL-2 receptor alpha (sIL-2R alpha) in the dialysate and serum of patients on continuous ambulatory peritoneal dialysis (CAPD). DESIGN AND PATIENTS: Samples from dialysate bags were collected during the initial month of dialysis. During peritonitis, samples were collected from the first three bags on the day of admittance to the hospital and from the night bags on days 3 and 10. Serum samples were drawn on days 1 and 10. RESULTS: IL-10 was detected in all dialysate samples except one on the first day of infection, with a peak median level of 50 pg/mL and a slow decrease thereafter. In serum the median levels never exceeded detectable levels. Patients infected with Escherichia coli or Staphylococcus aureus had higher IL-10 levels in dialysate on day 3 as compared to the remaining patients (p < 0.05). If the catheter had to be drawn, because of persistent cloudy dialysate, the IL-10 levels remained elevated for a longer time (p < 0.05). IFN-gamma and IL-2 were detected only in the dialysate of patients infected with either S. aureus or S. epidermidis. Only one serum sample showed increased IFN-gamma. SIL-2R alpha was found in all the serum and dialysis samples from the first day of infection. Contrary to the analyzed cytokines, the receptor showed severalfold higher levels in serum as compared to the dialysate. During the infection the receptor levels in the dialysate increased, while they remained stationary in the serum, indicating a local production. CONCLUSION: This is the first time IL-10 has been demonstrated in the dialysate during peritonitis in CAPD patients. In view of its role as a suppressor of the immune and inflammatory responses, it is a potentially important observation, which might have clinical implications in the future.     

Changes in hemodynamic and metabolic parameters during controlled muscular exertion in a group of international-level professional cyclists

The behaviour of some cardiovascular and metabolic parameters have been studied in 11 competitive road-cyclists under controlled submaximal work load. The test used was intermittent with load increasing from 100 to 250 watt, independent from age and body weight of the athletes. The results obtained have shown that whereas the estimated VO2 was 4,76 LO2/min, the extrapolated VO2max goes up to 6,08 LO2/min, corresponding to 84,55 m102/Kg X min. Particularly interesting seems to be the way through which the high VO2 levels can be obtained in these subjects: small increment of the mean arterial blood pressure together with large oxygen extraction and high vasodilatation.     

Absence of regulation of human polymorphonuclear oxidative burst by interleukin-10, interleukin-4, interleukin-13 and transforming growth factor-beta in whole blood

PURPOSE: To develop an animal model of a fibrin- and platelet-rich intraluminal arterial thrombus with abnormal mural substrate to simulate in situ thrombosis of human atherosclerotic arteries. MATERIALS AND METHODS: Parallel studies of the crush-thrombin model (CT) and double-tuck model (DT) were performed and evaluated with use of angiography and histologic analysis. Ten Yorkshire swine (1-6 months; 20-30 kg; 10 females) underwent right femoral and carotid cutdowns performed after administration of general anesthesia (4 mL intravenous thiopental sodium, isoflurane 2% in 1 L of oxygen). After angiography, the CT model was created in the left carotid artery and the DT model was performed in the right carotid artery. Angiograms were obtained at 20 minutes (n = 1), at 1 hour (n = 3), at 2 hours (n = 4), and at 3 hours (n = 2) before sacrifice. After sacrifice, histologic specimens were stained with hematoxylin-eosin (H-E stain) and phosphotungstic acid hematoxylin for fibrin. The specimens were examined for endothelial irregularity and adhesion, platelet aggregation, fibrin layering, vessel wall injury, and adventitial hemorrhage. The findings were quantified as 0 = absent, 1+ = slight, 2+ = moderate, and 3+ = severe. RESULTS: Angiographic results were similar. However, histologic analysis of the CT model showed severe damage to the arterial wall with dissection in nine of 10 animals. In the DT model, no dissection was found (n = 10). Endothelial irregularity was found in six of 10 arteries treated with the CT method, as compared with nine of 10 arteries prepared with the DT model; endothelial adhesion was found in five DT arteries and in four CT arteries. Platelet aggregation was present equally in both methods. A fibrin- and platelet-rich thrombus was created in five of 10 examined arteries by both methods. CONCLUSIONS: The DT model creates endothelial irregularity leading to formation of a platelet- and fibrin-rich thrombus, adherent to the vessel wall without damage to the media. This contrasts with the CT method, which created medial dissection in nine of 10 arteries. One hour is the minimum time required to produce a good quality thrombus; 2 hours is the optimum time. The DT model is proposed as a useful tool in the development of new devices, drugs, and biotechnologic advances.     

Pityrosporum ovale extracts increase interleukin-4, interleukin-10 and IgE synthesis in patients with atopic eczema

The increasing number of cystic fibrosis (CF) mutations is a great obstacle to the use of DNA procedures in the detection of gene defects. We describe a fast, cheap and non-radioactive procedure, Reverse dot-blot analysis (RDB), for the simultaneous detection of CF mutations in the Italian population. We used this approach to study seven exons of the CF gene for 14 CF gene defects and were able to characterize 222 of 272 CF chromosomes (80%). The cost of the procedure was $25 per sample analysed.     

Interleukin-10 production by human carcinoma cell lines and its relationship to interleukin-6 expression

Recent data indicate a major role for IL-10 in suppressing immune and inflammatory reactions. To date, expression of human IL-10 has been attributed primarily to helper T lymphocytes, activated monocytes, and neoplastic B cells, and was often found to be associated with IL-6 expression. In this study we sought to determine whether non-hematopoietic human tumor cell lines produce IL-10 and, if so, what is the relationship between IL-10 and IL-6. Using ELISA, we determined IL-10 and IL-6 levels in culture supernatants of 48 cell lines established from carcinomas of the kidney, colon, breast and pancreas, malignant melanomas and neuroblastomas. IL-6 protein was secreted by 28 of the tumor cell lines; IL-10 was measurable in 15 cell lines. IL-6 secretion was maximal and most frequent in renal-cancer cell lines, while IL-10 production was found to be highest and most common among cell lines derived from colon carcinomas. IL-10 in conditioned medium of one of the colon carcinoma cell lines (CCL222) was bio-active, as demonstrated in the mouse MC/9 mast-cell-line assay and in human mixed-lymphocyte reactions. In both assays, IL-10 bio-activity was neutralized by an anti-IL-10 monoclonal antibody. Expression of IL-6 and IL-10 was confirmed by RNA analysis using message amplification by PCR and sequencing of amplified cDNA. LPS, IL-1 alpha, and TNF-alpha strongly enhanced the release of IL-6 by RCC cells, but only marginally affected IL-10 production in colon-carcinoma cells. IL-10 secretion by colon-carcinoma cells was moderately stimulated by IFN-gamma and IL-4. Dexamethasone suppressed the release of IL-6, but had no inhibitory effect on IL-10 secretion. Our results demonstrate that tumor cell lines established from certain types of human carcinomas are capable of expressing and releasing IL-6 and/or IL-10, suggesting a role of these cytokines in solid-tumor development and anti-tumor immunity.     

Modulated expression of the epidermal growth factor-like homeotic protein dlk influences stromal-cell-pre-B-cell interactions, stromal cell adipogenesis, and pre-B-cell interleukin-7 requirements

A close relationship exists between adipocyte differentiation of stromal cells and their capacity to support hematopoiesis. The molecular basis for this is unknown. We have studied whether dlk, an epidermal growth factor-like molecule that intervenes in adipogenesis and fetal liver hematopoiesis, affects both stromal cell adipogenesis and B-cell lymphopoiesis in an established pre-B-cell culture system. Pre-B-cell cultures require both soluble interleukin-7 (IL-7) and interactions with stromal cells to promote cell growth and prevent B-cell maturation or apoptosis. We found that BALB/c 3T3 fibroblasts express dlk and function as stromal cells. Transfection of these cells with antisense dlk decreased dlk expression and increased insulin-induced adipocytic differentiation. When antisense transfectants were used as stroma, IL-7 was no longer required to support the growth of pre-B cells and prevent maturation or apoptosis. Antisense dlk transfectants of S10 stromal cells also promoted pre-B-cell growth in the absence of IL-7. These results show that modulation of dlk on stromal cells can influence their adipogenesis and the IL-7 requirements of the pre-B cells growing in contact with them. These results indicate that dlk influences differentiation signals directed both to the stromal cells and to the lymphocyte precursors, suggesting that dlk may play an important role in the bone marrow hematopoietic environment.     

Interactions of erythropoietin, granulocyte colony-stimulating factor, stem cell factor, and interleukin-11 on murine hematopoiesis during simultaneous administration

We investigated how in vivo effects of single hematopoietic cytokines change if given in combination for a prolonged time. Mice were treated with every combination of recombinant human (rh) erythropoietin (EPO), rh granulocyte colony-stimulating factor (G-CSF), recombinant rat (rr) stem cell factor (SCF), and rh interleukin (IL)-11 by continuous infusion over 7 days (full factorial design with three dose levels for each cytokine). Burst-forming unit-erythroid (BFU-E), colony-forming unit-erythroid (CFU-E), and colony-forming unit-granulocyte-macrophage (CFU-GM) were determined in bone marrow and spleen, reticulocytes, hematocrit, granulocytes, and thrombocytes in the peripheral blood. An analysis of variance (ANOVA) and multiple comparison of means was used to evaluate the data. For several cell types, cytokine effects superimposed in an additive way if combined. However, in a large number of circumstances, nonadditive pairwise interactions were found. They differed in type and magnitude involving high-dose saturation, high-dose antagonistic effects, and even effect reversals (qualitative interactions). Hence, in general, it was not possible to foresee the combination effects on the basis of existing knowledge of single effects. On the other hand, the cytokine network was robust and no system hazards were observed under multiple cytokine combinations. The results illustrate that the cytokine network has nonlinear dynamic properties in vivo with dose-response characteristics of one cytokine being continuously modified by other cytokines.     

Modulation of human microvascular endothelial cell bioenergetic status and glutathione levels during proliferative and differentiated growth

During angiogenesis, formerly differentiated human microvascular endothelial cells (HMECs) return to a proliferative growth state. Many fundamental questions regarding HMEC function, such as how HMECs adapt to changes in bioenergetic requirements upon return to proliferative growth, remained unanswered. In this study, we evaluated whether modifications in HMEC bioenergetic profiles and glutathione (GSH) levels accompanied the cellular transition between differentiated and proliferative growth. To provide insight into the continuum of cellular adaptations that occur during this transition, we used a method recently developed in our laboratory that induces a state of morphological and functional predifferentiation in HMECs. Cellular morphology, in conjunction with flow cytometric DNA analyses and HMEC functional assays (the directed migration and intercellular association involved in microtubule formation) were employed to validate the HMEC culture state of growth. Analysis of the HPLC nucleotide profiles disclosed several findings common to all culture growth states. These uniform findings, e.g., cellular energy charges > 0.90, and highly reduced redox states, revealed that cultured HMECs maintain high rates of oxidative metabolism. However, there were also significant, culture growth state related differences in the nucleotide profiles. Proliferative HMECs were shown to possess significantly higher (relative to both large vessel endothelial cells, and differentiated HMECs) levels of GSH and specific nucleotides which were related with a return to the active cell cycle-ATP, GTP, UTP, and CTP, and NADPH. Further, the nucleotide profiles and GSH levels of the predifferentiated HMECs were determined to be intermediate between levels obtained for the proliferative and differentiated HMECs. The results of this study demonstrate that the capacity to modulate their cellular bioenergetic status during growth state transitions is one of the adaptations that enable HMECs to retain a growth state reciprocity. In addition, our findings also show that HMECs, especially during the proliferative growth state, are biochemically distinct from endothelial cells harvested from large vessels, and therefore suggest that HMECs are the cells of choice to employ when studying diseases that affect the human microvasculature.     

Distinct actions of interleukin-9 and interleukin-4 on a hematopoietic stem cell line, EMLC1

EMLC1 is a hematopoietic stem cell line that depends on stem cell factor (SCF) for growth and generates lymphoid, erythroid and myeloid progenitors in the presence of different cytokines. We have studied signaling events leading to cell proliferation and differentiation of EMLC1 mediated by interleukin (IL)-4 and IL-9. It was found that IL-9 enhances SCF-induced cell proliferation and promotes erythropoietin (EPO)-dependent erythroid differentiation of EMLC1 cells. However, IL-9 alone cannot support the growth of this cell line. In contrast, IL-4 by itself is sufficient to promote the growth of EMLC1 cells, even in the absence of SCF. Antiphosphotyrosine immunoblots of total cell lysates demonstrated that IL-4 and IL-9 induce tyrosine phosphorylation of different cellular substrates. Both IL-4 and IL-9 stimulated tyrosine phosphorylation of SHP-2, whereas the 90-kD tyrosine phosphorylated protein induced by IL-9 stimulation is Stat3. We have also shown that IL-4 is much more potent than IL-9 in inducing the expression of primary response gene c-myc. It was further determined that c-myc antisense oligodeoxynucleotide blocked IL-4 supported cell growth. Taken together, these results indicate that IL-4 may serve as a growth-promoting factor for hematopoietic stem cells, and IL-9 enhances both growth and erythroid differentiation of primitive hematopoietic progenitors. The results also suggest that differences in tyrosine phosphorylation induced by IL-4 and IL-9 may in part determine their distinct biological functions.     

Interleukin-4 and interleukin-10 are chondroprotective and decrease mononuclear cell recruitment in human rheumatoid synovium in vivo

We used the severe combined immunodeficient (SCID) mouse model to assess the effect of interleukin-4 (IL-4) or IL-10 injection on cartilage degradation and mononuclear cell (MNC) recruitment to human rheumatoid synovium in vivo. Human rheumatoid synovium and cartilage from five rheumatoid arthritis patients, obtained after joint replacement surgery, were engrafted subcutaneously to 6-8-week-old SCID CB17 mice. Synovial tissues were injected with recombinant human IL-4 (rhIL-4, 100 ng; rhIL-10, 100 ng), both cytokines, or tumour necrosis factor-alpha (TNF-alpha) (1000 U), or phosphate-buffered saline twice a week for 4 weeks. The graft was removed and immunochemical analysis was carried out to assess intracellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin expression. Moreover, cartilage degradation was assessed through the quantification of the erosion surface on a computerized image of the engrafted cartilage at high power view. MNC recruitment in the synovial tissue was determined by labelling blood MNC with indium-111 before their intraperitoneal injection. The activity obtained in the region of the graft were determined with a gamma camera 72 hr postinjection. The results are expressed as a percentage of initial injected activity. After 4 weeks we observed a decrease of cartilage area in controls (77 +/- 8%), inhibited after injection of IL-4, IL-10, or both cytokines (90 +/- 3%, 89.1 +/- 4%, 89.2 +/- 5% respectively), and 57 +/- 17% after TNF-alpha injection. The % MNC activity in the graft decreased to 77 +/- 81% (NS), 9 +/- 4% (P < 0.003) and 19 +/- 6% (P < 0.007) compared with untreated synovial tissue after treatment with IL-4, IL-10, or both cytokines, respectively. Moreover, IL-10 but not IL-4 decreased the expression of ICAM-1 but not VCAM-1 or E-selectin by synovial cells. These results suggest that IL-10 and IL-4 could have chondroprotective properties, and that IL-10 but not IL-4 inhibits MNC traffic towards the synovial tissue efficiently.