Interleukin-1β and Tumor Necrosis Factor-α Produce Distinct, Time-dependent Patterns of Acute Arthritis in the Rat Knee

Interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) synergistically induce and sustain arthritis. Two competing hypotheses of arthritis induction are 1) that TNF preferentially mediates inflammation, whereas IL-1 impels bone destruction, or 2) that either cytokine controls the entire process. In this study, these propositions were tested in two experiments by instilling IL-1β or TNF-α into one knee of Lewis rats ( n = 6/group) to incite arthritis, after which semiquantitative scores for inflammation, bone resorption, osteoclasts, and cartilage integrity were acquired. In the induction study, IL-1β or TNF-α (3, 10, or 30 μg) was given once to incite arthritis. After 2 days, IL-1β induced significant, dose-dependent increases in inflammation (mild to marked), bone resorption (minimal to moderate), and osteoclasts (minimal to moderate). In contrast, TNF-α induced minimal to mild inflammation but had little impact on resorption or osteoclasts. Both IL-1 and TNF (≥10 μg) yielded mild cartilage degeneration. Most lesion scores in TNF-treated rats were significantly lower than those in animals given the same dose of IL-1β. In the persistence study, rats were injected once with IL-1 or TNF (10 μg) and maintained for 2, 3, or 7 days. IL-1β significantly enhanced inflammation (all 3 days), bone resorption (days 2 and 3), osteoclasts (days 2 and 3), and cartilage matrix loss (days 2 and 3), whereas TNF-α augmented inflammation (days 2 and 3) and cartilage degeneration (day 2) but not bone resorption or osteoclasts. Thus, both IL-1β and TNF-α can launch inflammation, but IL-1β drives skeletal destruction.

Generalized Degenerative Joint Disease in Osteoprotegerin (Opg) Null Mutant Mice

Bone structure is modulated by the interaction between receptor activator of nuclear factor-κB (RANK) and RANK ligand (RANKL). Osteoprotegerin (OPG), a decoy receptor for RANKL, modifies osteoclast-mediated bone resorption directly and spares articular cartilage indirectly in rodents with immune-mediated arthritis by preventing subchondral bone destruction. The OPG/RANKL balance also seems to be critical in maintaining joint integrity in osteoarthritis, a condition featuring articular bone and cartilage damage in the absence of profound inflammation. The current study explored the role of OPG in sparing articular cartilage by evaluating joint lesions in adult C57BL/6J mice lacking osteoprotegerin (Opg (-) (/-)). At 3, 5, 7, 9, and 12 months of age, both sexes of Opg (-) (/-) mice developed severe degenerative joint disease (DJD) characterized by progressive loss of cartilage matrix and eventually articular cartilage. Lesions developed earlier and more severely in Opg (-) (/-) mice relative to age-matched, wild-type (Opg (+) (/+)), or heterozygous (Opg (+) (/-)) littermates (P ≤ .05). The femorotibial joint was affected bilaterally at 3 months, while other key weight-bearing diarthrodial joints (eg, coxofemoral, scapulohumeral, humeroradioulnar) were affected later and unilaterally. Cortical bone in subchondral plates and long bone diaphyses of Opg (-) (/-) mice but not Opg (+/+) or Opg (+) (/-) animals was osteoporotic by 3 months of age (P ≤ .05); the extent of porosity was less than the degree of DJD. Closure of the physes in long bones (P ≤ .05) and cartilage retention in the femoral primary spongiosa (P ≤ .05) affected chiefly Opg (-) (/-) mice. These data suggest that OPG plays an essential direct role in maintaining cartilage integrity in the articular surfaces and physes.

RANKL inhibition by osteoprotegerin prevents bone loss without affecting local or systemic inflammation parameters in two rat arthritis models: comparison with anti-TNFalpha or anti-IL-1 therapies

INTRODUCTION

Rat adjuvant-induced arthritis (AIA) and collagen-induced arthritis (CIA) feature bone loss and systemic increases in TNFalpha, IL-1beta, and receptor activator of NF-kappaB ligand (RANKL). Anti-IL-1 or anti-TNFalpha therapies consistently reduce inflammation in these models, but systemic bone loss often persists. RANKL inhibition consistently prevents bone loss in both models without reducing joint inflammation. Effects of these therapies on systemic markers of bone turnover and inflammation have not been directly compared.

METHODS

Lewis rats with established AIA or CIA were treated for 10 days (from day 4 post onset) with either PBS (Veh), TNFalpha inhibitor (pegsunercept), IL-1 inhibitor (anakinra), or RANKL inhibitor (osteoprotegerin (OPG)-Fc). Local inflammation was evaluated by monitoring hind paw swelling. Bone mineral density (BMD) of paws and lumbar vertebrae was assessed by dual X-ray absorptiometry. Markers and mediators of bone resorption (RANKL, tartrate-resistant acid phosphatase 5b (TRACP 5B)) and inflammation (prostaglandin E2 (PGE2), acute-phase protein alpha-1-acid glycoprotein (alpha1AGP), multiple cytokines) were measured in serum (day 14 post onset).

RESULTS

Arthritis progression significantly increased paw swelling and ankle and vertebral BMD loss. Anti-TNFalpha reduced paw swelling in both models, and reduced ankle BMD loss in AIA rats. Anti-IL-1 decreased paw swelling in CIA rats, and reduced ankle BMD loss in both models. Anti-TNFalpha and anti-IL-1 failed to prevent vertebral BMD loss in either model. OPG-Fc reduced BMD loss in ankles and vertebrae in both models, but had no effect on paw swelling. Serum RANKL was elevated in AIA-Veh and CIA-Veh rats. While antiTNFalpha and anti-IL-1 partially normalized serum RANKL without any changes in serum TRACP 5B, OPG-Fc treatment reduced serum TRACP 5B by over 90% in both CIA and AIA rats. CIA-Veh and AIA-Veh rats had increased serum alpha1AGP, IL-1beta, IL-8 and chemokine (C-C motif) ligand 2 (CCL2), and AIA-Veh rats also had significantly greater serum PGE2, TNFalpha and IL-17. Anti-TNFalpha reduced systemic alpha1AGP, CCL2 and PGE2 in AIA rats, while anti-IL-1 decreased systemic alpha1AGP, IL-8 and PGE2. In contrast, RANKL inhibition by OPG-Fc did not lessen systemic cytokine levels in either model.

CONCLUSIONS

Anti-TNFalpha or anti-IL-1 therapy inhibited parameters of local and systemic inflammation, and partially reduced local but not systemic bone loss in AIA and CIA rats. RANKL inhibition prevented local and systemic bone loss without significantly inhibiting local or systemic inflammatory parameters.

Anti-inflammatory and cartilage-protecting effects of an intra-articularly injected anti-TNF{alpha} single-chain Fv antibody (ESBA105) designed for local therapeutic use

OBJECTIVES

(1) To show that a single-chain Fv antibody (scFv) against tumour necrosis factor alpha (TNFalpha) (ESBA105) has efficacy comparable to a full length anti-TNFalpha IgG (infliximab); (2) to evaluate whether ESBA105 has all the properties required for the local treatment of arthritis; and (3) to investigate its discriminative tissue penetration properties.

METHODS

In vivo efficacy was measured in arthritis of the knee joint induced by the intra-articular injection of recombinant human TNFalpha (rhTNFalpha) in Lewis rats. Cartilage penetration of scFv (ESBA105) and full length IgG (infliximab) were studied in bovine cartilage specimens ex vivo. Tissue penetration, biodistribution and pharmacokinetics of ESBA105 were followed and compared after intra-articular and intravenous administration.

RESULTS

In cell culture, ESBA105 showed similar TNFalpha inhibitory potency to infliximab. In vivo, ESBA105 inhibited rhTNFalpha-induced synovial inflammation in rats with efficacy again comparable to infliximab. An 11-fold molar excess of ESBA105 over rhTNFalpha resulted in 90% inhibition of knee joint swelling, inflammatory infiltrates and proteoglycan loss from cartilage. In ex vivo studies of bovine cartilage, ESBA105 penetrated well into the cartilage whereas infliximab remained on the surface. In vivo, rapid penetration into the synovial tissue, cartilage and surrounding tissues was observed following intra-articular injection of [(125)I]-ESBA105 into the knee joint of rabbits.

CONCLUSIONS

ESBA105 potently inhibits inflammation and prevents cartilage damage triggered by TNFalpha. In contrast to a full length IgG, ESBA105 also penetrates into cartilage and can be expected to reverse the TNFalpha-induced catabolic state of articular cartilage in arthritides.

RANKL is a marker and mediator of local and systemic bone loss in two rat models of inflammatory arthritis

RANKL is an essential mediator of bone erosions, but the role of RANKL in systemic bone loss had not been studied in arthritis. RANKL protein was increased in rat joint extracts and serum at the earliest stages of arthritis. Osteoprotegerin (OPG) treatment reversed local and systemic bone loss, suggesting that RANKL is both a marker and mediator of bone loss in arthritis.

INTRODUCTION

RANKL is well established as an essential mediator of bone erosions in inflammatory arthritis, but the role of RANKL in systemic bone loss in arthritis had not been studied. We hypothesized that serum RANKL could serve as both a mediator and as a novel biomarker for local and systemic bone loss in arthritis. We challenged this hypothesis in two established rat models of inflammatory arthritis. We sought to determine whether serum RANKL was elevated early in disease progression and whether RANKL suppression could prevent both local and systemic bone loss in these models.

MATERIALS AND METHODS

Detailed time-course studies were conducted in animals with collagen-induced (CIA) or adjuvant-induced (AIA) arthritis to evaluate the onset and progression of inflammation (paw swelling), bone erosions, osteoclast numbers, and RANKL protein levels in arthritic joints and in serum. Additional CIA and AIA rats (n=8/group) received placebo (PBS) or recombinant OPG (3 mg/kg three times weekly) for 10 days beginning 4 days after disease onset (first macroscopic evidence of hind paw erythema and edema) to assess the role of RANKL in local and systemic bone loss.

RESULTS

RANKL protein was significantly elevated in the joints and serum of CIA and AIA rats within 1-2 days of disease onset. Increased RANKL levels were associated with local (hind paw) and systemic (vertebral) osteopenia in both models. The RANKL inhibitor OPG prevented local and systemic osteopenia in both models of established disease.

CONCLUSIONS

RANKL protein is significantly increased both locally and systemically during the earliest stages of inflammatory arthritis in rats, suggesting that serum RANKL might have prognostic value for bone erosions and systemic osteopenia in this condition. RANKL inhibition through OPG prevented local and systemic bone loss in these arthritis models, suggesting that RANKL inhibition is a promising new approach for treating bone loss in arthritis.

Ethanol-Induced Inhibition of Bone Formation in a Rat Model of Distraction Osteogenesis: A Role for the Tumor Necrosis Factor Signaling Axis

BACKGROUND

Chronic ethanol exposure inhibits the rapid bone formation demonstrated during limb lengthening by distraction osteogenesis (DO). This inhibition is attenuated by simultaneous administration of antagonists to the cytokines interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha. The individual effects on inhibition of osteogenesis by these cytokines were tested. We hypothesized that administration of individual antagonists to these cytokines [IL-1 receptor antagonist (IL-1ra) or polyethylene glycol-conjugated soluble TNF receptor type 1 (sTNFR1)] would enhance DO and that the individual administration of each cytokine [recombinant rat (rr) IL-1 or recombinant rat (rr) TNF] would inhibit DO.

METHODS

Rats were either infused with a liquid diet with or without ethanol (antagonist studies) or given rat chow (recombinant studies) and underwent tibial fractures stabilized with external fixators for DO. The bioactive substances were administered by systemic (antagonist studies) or local (recombinant) diffusion.

RESULTS

A comparison of histologic sections from these distracted tibias demonstrated a protective effect on bone formation by sTNFR1 (p<0.05), unexpectedly, an IL-1ra-related decrease in bone formation (p<0.02), significant decreases in bone formation with rrTNF compared with the vehicle controls (p<0.02), and no significant changes in bone formation with rrIL-1. The cellular responses (fibroblastic and inflammatory cells) were unique for each recombinant cytokine administered.

CONCLUSIONS

These results suggest that the osteoinhibitory effects of chronic ethanol exposure are mediated in part by the TNF signaling axis.

Additive bone-protective effects of anabolic treatment when used in conjunction with RANKL and tumor necrosis factor inhibition in two rat arthritis models

OBJECTIVE

To investigate whether the bone-preserving effects of a RANKL antagonist or a tumor necrosis factor (TNF) antagonist could be further improved by the addition of a bone anabolic agent in inflammatory arthritis.

METHODS

Lewis rats with either adjuvant-induced arthritis (AIA) or collagen-induced arthritis (CIA) were treated for 10 days with PEGylated soluble tumor necrosis factor receptor type I (PEG sTNFRI), interleukin-1 receptor antagonist (IL-1Ra), osteoprotegerin (OPG), parathyroid hormone (PTH), or combinations of these agents starting on day 4 after disease onset. Treatment effects were assessed clinically, radiologically, and histologically, and by morphometry for the extent of paw swelling, bone erosive changes, and synovial inflammation.

RESULTS

Paw swelling and synovial inflammation were significantly inhibited by PEG sTNFRI in AIA and CIA, and by IL-1Ra in CIA. OPG and PTH had no significant effect on these parameters. Analysis of bone erosion revealed a significant bone-sparing effect of monotherapy with PEG sTNFRI or OPG in both models, whereas IL-1Ra was only effective in CIA. PTH treatment alone did not show a bone-protective effect in either model. With the combination of PEG sTNFRI and PTH, erosion scores (-74% in AIA and -61% in CIA versus controls) were significantly lower than those elicited by PEG sTNFRI alone (-41% and -29%, respectively, versus controls). Similar results were also obtained with the combination of OPG and PTH (-88% in AIA and -73% in CIA, compared with -70% and -55%, respectively, with OPG monotherapy). Coadministration of IL-1Ra and PTH had no synergistic bone-sparing effect. Morphometric analysis revealed that the addition of PTH to PEG sTNFRI or OPG resulted in higher bone volume and higher osteoblast numbers in both AIA and CIA.

CONCLUSION

The bone-protective effects resulting from RANKL or TNF antagonism can be further improved by the addition of a bone anabolic agent.

Role of interleukin-1 and tumor necrosis factor alpha in matrix degradation of human osteoarthritic cartilage

OBJECTIVE

To determine whether interleukin-1 (IL-1) or tumor necrosis factor alpha (TNFalpha), or both, plays a role in the excessive degradation that is observed in cultured osteoarthritic (OA) articular cartilage.

METHODS

Antagonists of IL-1 and TNFalpha, namely, IL-1 receptor antagonist and the PEGylated soluble TNFalpha receptor I, respectively, were added at different concentrations to explant cultures of nonarthritic (5 obtained at autopsy) and OA (15 obtained at arthroplasty) articular cartilage. The cleavage of type II collagen (CII) by collagenase was measured by an immunoassay in cartilage and culture media. Proteoglycan (mainly aggrecan) content and degradation were measured by a colorimetric assay for glycosaminoglycan (GAG) content in cartilage and culture media. Reverse transcriptase-polymerase chain reaction was used to analyze gene expression of matrix metalloproteases (MMPs) 1, 3, and 13, CII, aggrecan, IL-1, and TNFalpha.

RESULTS

Antagonists of IL-1 and TNFalpha inhibited the increase in CII cleavage by collagenase as well as the increase in GAG release observed in OA cartilage compared with normal cartilage. Inhibition was significant in tissue from some patients but not from others, although significant inhibition was observed when all the results were analyzed together. An increase in the GAG content in cartilage was seen in 4 of 15 cases. However, this increase was not significant when all the data were combined. Preliminary results indicated no effect of these antagonists on nonarthritic cartilage from 3 different donors. Independent analyses of gene expression in cultured cartilage from 9 other OA patients revealed that IL-1 or TNFalpha blockade, either alone and/or in combination, frequently down-regulated MMP-1, MMP-3, and MMP-13 expression. Expression of IL-1 and TNFalpha was inhibited by either antagonist or by the combination in essentially half the cases. The combined blockade up-regulated aggrecan and CII gene expression in approximately half the cases.

CONCLUSION

These results suggest that the autocrine/paracrine activities of TNFalpha and IL-1 in articular cartilage may play important roles in cartilage matrix degradation in OA patients but not in all patients. Inhibition of either or both of these cytokines may offer a useful therapeutic approach to the management of OA by reducing gene expression of MMPs involved in cartilage matrix degradation and favoring its repair.

Analysis of the kinetics of osteoclastogenesis in arthritic rats

OBJECTIVE

To analyze the kinetics of osteoclastogenesis in 2 models of chronic immune-mediated arthritis and 1 model of acute arthritis.

METHODS

Adjuvant-induced arthritis (AIA) and collagen-induced arthritis (CIA) in Lewis rats were used as models of chronic arthritis. Acute arthritis was induced in Lewis rats by injecting carrageenan into the hind paw. Osteoclasts were identified by cathepsin K immunohistochemistry at various time points after the onset of arthritis. The location, size, and nucleation of osteoclasts were also analyzed.

RESULTS

In both AIA and CIA, multinucleated and cathepsin K-positive osteoclasts first were observed on the day of disease onset. Initially, osteoclasts were localized at the periosteum next to the synovial membrane and in subchondral bone channels. The number, size, and nucleation of osteoclasts rapidly increased, leading to severe bone loss within days after disease onset. In addition, numerous mononucleated cathepsin K-positive osteoclast precursor cells emerged in the synovial membrane. All osteoclasts (cathepsin K-positive, multinucleated, attached to bone) and osteoclast precursors (cathepsin K-positive, mononucleated or multinucleated, within synovial tissue) were also positive for a macrophage-specific marker. Upon induction of acute arthritis with carrageenan, osteoclasts formed transiently in subchondral bone, but regressed 7 days after disease onset.

CONCLUSION

Functional osteoclasts are generated at the earliest stage of arthritis, and new precursors are continuously formed in the synovial membrane to replenish the osteoclast pool. These data indicate that anti-resorptive therapies may provide the most effective bone protection, when treatment is started soon after the onset of arthritis.

IL-1 and TNF Antagonists Prevent Inhibition of Fracture Healing by Ethanol in Rats

We tested the hypothesis that combined administration of IL-1 and TNF antagonists would protect fracture healing from inhibition by chronic ethanol exposure. Adult male rats were fed a liquid diet +/- ethanol (CON and ETOH) by intragastric infusion for three weeks prior to and three weeks after creation of an externally fixated tibial fracture. Beginning the day of fracture, one-half of each dietary group received 2.0 mg/kg/day IL-1ra and 2.0 mg/kg/2-days sTNFR1 (CON + ANTAG and ETOH + ANTAG), while all other animals received vehicle alone (CON + VEH and ETOH + VEH). Scoring of ex vivo radiographs and analysis by pQCT revealed a significantly lower incidence of bridging and reduced total mineral content in the ETOH + VEH group compared to all other groups. These results support, for the first time, the hypothesis that IL-1 and TNF antagonists are capable of protecting fracture healing from the inhibition associated with chronic ethanol consumption.

Osteoclast numbers in Lewis rats with adjuvant-induced arthritis: identification of preferred sites and parameters for rapid quantitative analysis

This study defined the best site for quantifying osteoclasts in male Lewis rats with mycobacteria-induced adjuvant arthritis. Hind paw sections of normal and arthritic rats (n = 6 per group) taken 7 days after disease onset were stained for osteoclasts using an anti-human cathepsin K primary antibody. Erosions and osteoclasts were assessed using semiquantitative scores (entire section) and quantitative measures (in calcaneus, navicular tarsal, and tibia). Bone area in arthritic rats was significantly reduced (P </= 0.05) by 39-55%, with the greatest decrease in the tarsal. Osteoclasts in arthritic rats were significantly increased (P </= 0.05) relative to normal in calcaneus (sevenfold), tarsal (194-fold), and tibia (threefold). The most useful quantitative indices were bone area and total osteoclasts, both defined as a percentage of total area measured. Semiquantitative scores for bone erosion and osteoclasts paralleled the quantitative indices. These data show that the navicular tarsal is the most sensitive site at which to assess arthritis in rats with this variant of adjuvant-induced arthritis.

Design of PEGylated soluble tumor necrosis factor receptor type I (PEG sTNF-RI) for chronic inflammatory diseases

A recombinant C-terminal truncated form of the human soluble tumor necrosis factor receptor type I (sTNF-RI) was produced in E. coli. This soluble receptor contains the first 2.6 of the 4 domains of the intact sTNF-RI molecule. A monoPEGylated form of this molecule was produced using a 30 kD methoxyPEG aldehyde with approximately 85% selectivity for the N-terminal amino group. This molecule was shown to be less immunogenic in primates than the full length (4.0 domain) molecule or other versions of sTNF-RI which were either PEGylated at different sites or with different molecular weight PEGs. The 30 kD PEG also has a longer serum half-life to the molecule than lower molecular weight PEGs. This molecule markedly blunts the inflammatory response in a number of rheumatoid arthritis animal models. In addition, phase I/II and early phase II data in humans indicate that PEG sTNF-RI is non-immunogenic and that weekly dosing with this drug can reduce the number of tender and swollen joints in rheumatoid arthritis patients. PEG sTNF-RI has comparable American College of Rheumatology (ACR) efficacy scores as other anti-TNF molecules currently used to treat rheumatoid arthritic patients.

Single and combined inhibition of tumor necrosis factor, interleukin-1, and RANKL pathways in tumor necrosis factor-induced arthritis: Effects on synovial inflammation, bone erosion, and cartilage destruction

OBJECTIVE

To investigate the efficacy of single and combined blockade of tumor necrosis factor (TNF), interleukin-1 (IL-1), and RANKL pathways on synovial inflammation, bone erosion, and cartilage destruction in a TNF-driven arthritis model.

METHODS

Human TNF-transgenic (hTNFtg) mice were treated with anti-TNF (infliximab), IL-1 receptor antagonist (IL-1Ra; anakinra), or osteoprotegerin (OPG; an OPG-Fc fusion protein), either alone or in combinations of 2 agents or all 3 agents. Synovial inflammation, bone erosion, and cartilage damage were evaluated histologically.

RESULTS

Synovial inflammation was inhibited by anti-TNF (-51%), but not by IL-1Ra or OPG monotherapy. The combination of anti-TNF with either IL-1Ra (-91%) or OPG (-81%) was additive and almost completely blocked inflammation. Bone erosion was effectively blocked by anti-TNF (-79%) and OPG (-60%), but not by IL-1Ra monotherapy. The combination of anti-TNF with IL-1Ra, however, completely blocked bone erosion (-98%). Inhibition of bone erosion was accompanied by a reduction of osteoclast numbers in synovial tissue. Cartilage destruction was inhibited by anti-TNF (-43%) and was weakly, but not significantly, inhibited by IL-1Ra, but was not inhibited by OPG monotherapy. The combination of anti-TNF with IL-1Ra was the most effective double combination therapy in preventing cartilage destruction (-80%). In all analyses, the triple combination of anti-TNF, IL-1Ra, and OPG was not superior to the double combination of anti-TNF and IL-1Ra.

CONCLUSION

Articular changes caused by chronic overexpression of TNF are not completely blockable by monotherapies that target TNF, IL-1, or RANKL. However, combined approaches, especially the combined blockade of TNF and IL-1 and, to a lesser extent, TNF and RANKL, lead to almost complete remission of disease. Differences in abilities to block synovial inflammation, bone erosion, and cartilage destruction further strengthen the rationale for using combined blockade of more than one proinflammatory pathway.

Prevention of primary non-function of islet xenografts in autoimmune diabetic NOD mice by anti-inflammatory agents

AIMS/HYPOTHESIS

High levels of inflammation locally in the graft during the initial days after transplantation can cause primary non-function (PNF) of grafted xenogeneic islets in NOD mice. The aim of this study was to explore in a model of spontaneous diabetes, the NOD mouse, the potential of anti-inflammatory agents in the prevention of PNF after xenogeneic islet transplantation.

METHODS

Spontaneously diabetic NOD mice were transplanted with 300 rat islets. Animals were treated with acetylsalicylic acid (AsA), rofecoxib, TGF-beta or IL-1 receptor antagonist (IL-1ra). Intra-graft expression of inflammation-related molecules was measured by real time PCR 8 h post-transplantation. At the same time point, plasma nitrite levels were measured.

RESULTS

Xenogeneic islets transplanted in control spontaneously diabetic mice resulted in PNF in 16 out of 38 mice (42%). Initial graft loss was not altered by administration of rofecoxib (30%) or TGF-beta (25%). AsA reduced the rate of rapid graft loss to 8% ( p<0.05 vs controls) and administration of IL-1ra even totally prevented PNF (0%, p<0.05 vs controls). Furthermore, all therapies prolonged the mean survival time of xenogeneic islet grafts. The inhibition of PNF by AsA was associated with decreased intra-islet levels of inflammation-related molecules (IL-1, TNF-alpha, iNOS, COX-2) and chemokines (MCP-1 and MIP-3alpha). Finally, also a diminished production of systemic nitrite levels was observed in AsA- and IL-1ra-treated islet recipients.

CONCLUSIONS/INTERPRETATION

These data show that treatment with AsA or IL-1ra prevents PNF after islet transplantation in spontaneously diabetic NOD mice. Moreover, the involvement of non-specific inflammation is recognized in xenogeneic islet PNF in spontaneously diabetic NOD mice.

Interleukin-1 and tumor necrosis factor antagonists attenuate ethanol-induced inhibition of bone formation in a rat model of distraction osteogenesis

Chronic ethanol exposure inhibits rapid bone formation during distraction osteogenesis (DO; fracture and limb lengthening) and decreases volumetric bone mineral density (BMD) in a model of intragastric dietary infusion [total enteral nutrition (TEN)] in the rat. The hypothesis tested herein was that overexpression of interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha mediates these deleterious effects of ethanol on the rat skeleton. Two studies (study 1, female rats; study 2, male rats) were performed to test the potential protective effects of the IL-1 and TNF antagonists: IL-1 receptor antagonist (IL-1ra) and 30-kDa polyethylene glycol-conjugated soluble TNF receptor type 1 (sTNFR1). All rats were infused with a liquid diet +/- ethanol (EtOH) and underwent tibial fractures and DO. During distraction, the animals received a combination of IL-1ra (1.8-2.0 mg/kg/day) and sTNFR1 (2.0 mg/kg/2 days) or vehicle. A comparison of distracted tibial histological sections demonstrated 1) significant antagonist-related increases in bone column formation over the EtOH controls (studies 1 and 2), and 2) restoration of new bone equivalent to that of the TEN controls (study 2). In contrast, examination of intact proximal tibial metaphyses by peripheral quantitative computerized tomography revealed decreases in volumetric BMD of both EtOH control and EtOH antagonist groups (study 2). These results demonstrate that short-term systemic administration of IL-1 and TNF antagonists together protect rapid bone formation during DO from the deleterious effects of chronic ethanol but are ineffective in regard to intact bone homeostasis.

Inhibition of interleukin-1 but not tumor necrosis factor suppresses neovascularization in rat models of corneal angiogenesis and adjuvant arthritis

OBJECTIVE

To assess the capacities of the cytokine inhibitors interleukin-1 receptor antagonist (IL-1Ra; anakinra) and PEGylated soluble tumor necrosis factor receptor I (PEG sTNFRI; pegsunercept) to suppress neovascularization.

METHODS

A corneal angiogenesis assay was performed by implanting nylon discs impregnated with an angiogenic stimulator (basic fibroblast growth factor or vascular endothelial growth factor) into one cornea of female Sprague-Dawley rats. Animals were treated with IL-1Ra or PEG sTNFRI for 7 days, after which new vessels were quantified. In a parallel study, male Lewis rats with mycobacteria-induced adjuvant-induced arthritis were treated with IL-1Ra or PEG sTNFRI for 7 days beginning at disease onset, after which scores for inflammation and bone erosion as well as capillary counts were acquired from sections of arthritic hind paws.

RESULTS

Treatment with IL-1Ra yielded a dose-dependent reduction in growth factor-induced corneal angiogenesis, while PEG sTNFRI did not. IL-1Ra, but not PEG sTNFRI, significantly reduced the number of capillaries in arthritic paws, even though both anticytokines reduced inflammation and bone erosion to a similar degree.

CONCLUSION

These data support a major role for IL-1, but not TNFalpha, in angiogenesis and suggest that an additional antiarthritic mechanism afforded by IL-1 inhibitors, but not anti-TNF agents, is the suppression of the angiogenic component of pannus.

Duration of bone protection by a single osteoprotegerin injection in rats with adjuvant-induced arthritis

Daily osteoprotegerin (OPG) injection for 7 or more days prevents bone loss for 3 weeks in rats with adjuvant-induced arthritis (AdA). The present experiments defined the duration of bone protection in AdA provided by a single OPG bolus. Male Lewis rats received OPG at the onset or peak of clinical disease, after which bone mineral density (BMD), erosions, and osteoclasts were evaluated. An OPG bolus (4 mg/kg subcutaneously) at onset eliminated osteoclasts, preserved BMD for 7 days, and prevented bone erosions for 4 days. In contrast, an OPG bolus (1, 3, 10, or 30 mg/kg intravenously) given at the peak of disease eradicated osteoclasts in a dose-dependent manner but had no impact on bone integrity due to extensive pre-existing bone loss. These data indicate that one OPG injection will inhibit joint erosions for several days, and confirm that bone-sparing therapy must be initiated early in disease to protect joint integrity.

Kinetics of bone protection by recombinant osteoprotegerin therapy in Lewis rats with adjuvant arthritis

OBJECTIVE

To assess the effect of different dosages and treatment schedules of osteoprotegerin (OPG) on joint preservation in an experimental model of adjuvant-induced arthritis (AIA).

METHODS

Male Lewis rats with AIA (6-8 per group) were treated with a subcutaneous bolus of recombinant human OPG according to one of the following schedules: daily OPG (an efficacious regimen) starting at disease onset (days 9-15), early intervention (days 9-11), delayed intervention (days 13-15), and extended therapy (days 9-22). Inflammation (hind paw swelling) was quantified throughout the clinical course; osteoporosis (bone mineral density [BMD], by quantitative dual x-ray absorptiometry) and morphologic appraisals of inflammation, bone damage, intralesional osteoclasts (by semiquantitative histopathologic scoring), and integrity of the articular cartilage matrix (by retention of toluidine blue stain) were determined in histology sections of arthritic hind paws.

RESULTS

OPG provided dose- and schedule-dependent preservation of BMD and periarticular bone while essentially eliminating intralesional osteoclasts. Dosages > or = 2.5 mg/kg/day preserved or enhanced BMD and prevented essentially all erosions. A dosage of 4 mg/kg/day protected joint integrity to a comparable degree when given for 7 (days 9-15) or 14 (days 9-22) consecutive days. At this dosage, early intervention (days 9-11) was twice as effective as delayed intervention (days 13-15) at preventing joint dissolution. Erosions and osteoclast scores were greatly decreased for 26 days (measured from the first treatment) after 7 or 14 daily doses of OPG (4 mg/kg/day). OPG treatment also prevented loss of cartilage matrix proteoglycans, an indirect consequence of protecting the subchondral bone. No OPG dosage or regimen alleviated weight loss, inflammation, or periosteal osteophyte production.

CONCLUSION

These data indicate that OPG preserves articular bone and (indirectly) articular cartilage in arthritic joints in a dose- and schedule-dependent manner, halts bone erosion when given at any point during the course of arthritis, produces sustained antierosive activity after a short course, and is most effective when initiated early in the disease.

Development of a novel, nonimmunogenic, soluble human TNF receptor type I (sTNFR-I) construct in the baboon

Pharmacokinetics and immunogenicity of six different recombinant human soluble p55 tumor necrosis factor (TNF) receptor I (sTNFR-I) constructs were evaluated in juvenile baboons. The constructs included either an sTNFR-I IgG1 immunoadhesin (p55 sTNFR-I Fc) or five different sTNFR-I constructs covalently linked to polyethylene glycol. The constructs were administered intravenously three times, and pharmacokinetics and immunogenicity were examined over 63 days. All of the constructs were immunogenic, with the exception of a 2.6-domain monomeric sTNFR-I. To evaluate whether the nonimmunogenic 2.6-domain monomeric construct could protect baboons against TNF-alpha-induced mortality, baboons were pretreated with 1, 5, or 10 mg/kg body wt and were compared with baboons receiving either placebo or 1 mg/kg body wt of the dimeric 4.0-domain sTNFR-I construct (n = 3 each) before lethal Escherichia coli bacteremia. The monomeric construct protected baboons and neutralized TNF bioactivity, although greater quantities were required compared with the dimeric 4.0-domain sTNFR-I construct. We conclude that E. coli-recombinant-derived human sTNFR-I constructs can be generated with minimal immunogenicity on repeated administration and still protect against the consequences of exaggerated TNF-alpha production.

Anti-interleukin-1 therapy in rheumatic diseases

Recent research has shown that in the processes of rheumatoid arthritis (RA), interleukin (IL)-1 is one of the pivotal cytokines in initiating disease, and the body's natural response, IL-1 receptor antagonist (IL-1Ra), has been shown conclusively to block its effects. In laboratory and animal studies inhibition of IL-1 by either antibodies to IL-1 or IL-1Ra proved beneficial to the outcome. To date, two large well-controlled studies in patients with RA led to the conclusion that IL-1Ra is clinically effective and that it slows progression of bone damage as measured radiographically. Being a specific, selective inhibitor of the IL-1 pathway, IL-1Ra could constitute an important new approach to treating patients with RA that significantly reduces the signs and symptoms of the disease, reduces joint destruction and up to now has proved safe and well tolerated.

Anti-interleukin-1 and anti-tumor necrosis factor-alpha synergistically inhibit adjuvant arthritis in Lewis rats

Interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) play dominant roles in mediating the progression of many inflammatory joint diseases, including rheumatoid arthritis in humans, collagen-induced arthritis in mice and rats, and adjuvant arthritis in rats. Blockade of either cytokine partially controls these diseases. The present study investigated the value of combination anti-cytokine therapy in arthritis: the efficacy of IL-1 receptor antagonist (IL-1ra) and 30 kDa polyethylene glycol (PEG)-conjugated soluble TNF receptor type I (PEG sTNF-RI) given together was assessed in Lewis rats with adjuvant arthritis. Administration of either IL-1ra or PEG sTNF-RI partially alleviated joint inflammation, loss of bone mineral density, and loss of body weight. In contrast, combination of these anti-cytokine treatments exhibited a synergistic capacity to inhibit these changes, even when combining doses of IL-1ra and PEG sTNF-RI that did not affect lesion severity when used alone. Statistical analysis of these adjuvant arthritis data using the isobologram method proved that IL-1ra and PEG sTNF-RI were clearly synergistic in inhibiting inflammation, loss of bone mineral density, loss of body weight, and histopathologic parameters of inflammation and joint destruction. These results suggest that treating autoimmune arthritic diseases with combinations of anti-IL-1 and anti-TNF molecules will achieve superior efficacy compared to the use of a single class of anti-cytokine agent and may allow for dose reductions that could prove useful in minimizing potential side effects.

Activated T cells regulate bone loss and joint destruction in adjuvant arthritis through osteoprotegerin ligand

Bone remodelling and bone loss are controlled by a balance between the tumour necrosis factor family molecule osteoprotegerin ligand (OPGL) and its decoy receptor osteoprotegerin (OPG). In addition, OPGL regulates lymph node organogenesis, lymphocyte development and interactions between T cells and dendritic cells in the immune system. The OPGL receptor, RANK, is expressed on chondrocytes, osteoclast precursors and mature osteoclasts. OPGL expression in T cells is induced by antigen receptor engagement, which suggests that activated T cells may influence bone metabolism through OPGL and RANK. Here we report that activated T cells can directly trigger osteoclastogenesis through OPGL. Systemic activation of T cells in vivo leads to an OPGL-mediated increase in osteoclastogenesis and bone loss. In a T-cell-dependent model of rat adjuvant arthritis characterized by severe joint inflammation, bone and cartilage destruction and crippling, blocking of OPGL through osteoprotegerin treatment at the onset of disease prevents bone and cartilage destruction but not inflammation. These results show that both systemic and local T-cell activation can lead to OPGL production and subsequent bone loss, and they provide a novel paradigm for T cells as regulators of bone physiology.

Dexamethasone enhances CTLA-4 expression during T cell activation

T cell activation is enhanced by the costimulatory interaction of B7 on antigen-presenting cells and CD28 on T cells, resulting in long-term T cell proliferation, differentiation and production of large amounts of cytokines, such as interleukin (IL)-2. CTLA-4 is a co-stimulation receptor that shares 31% homology with CD28 and binds B7 family members with higher affinity. CTLA-4 is transiently expressed intracellularly and on the cell surface following activation of T cells. We have studied the kinetics of CTLA-4 expression and the effects of dexamethasone on CTLA-4 expression during T cell activation in cultures of mouse spleen cells stimulated by a mixture of immobilized anti-CD3 and anti-CD28 monoclonal antibodies (anti-CD3/CD28 mAb) or concanavalin A (ConA). CTLA-4 expression peaked on day 2 and returned to background levels after 7 days. Dexamethasone was found to potentiate CTLA-4 expression in a dose-dependent manner with an EC50 effective concentration 50%) of about 10(-8) M. In contrast, other immunosuppressive agents, such as rapamycin or cyclosporin A had no or an inhibitory effect on CTLA-4 expression, respectively. Dexamethasone also stimulated CD28 expression, but inhibited IL-2R expression during anti-CD3/CD28 mAb-induced mouse splenic T cell activation. Western blot analyses of lysates of activated mouse T cells showed that dexamethasone increased CTLA-4 protein levels twofold during anti-CD3/CD28 mAb-induced activation. Dexamethasone also enhanced CTLA-4 messenger RNA twofold as quantified by ribonuclease protection assay. The effects of dexamethasone on CTLA-4 expression were glucocorticoid-specific and completely inhibited by the glucocorticoid receptor antagonist mifepristone (RU486), indicating that the effect of dexamethasone on CTLA-4 expression is mediated through the glucocorticoid receptor. In conclusion, the immunosuppressive agent dexamethasone actually stimulates CTLA-4 expression, which is involved in downregulation of T cell activation.

Infection, autoimmunity and autoimmune disease

Studies of the immune response of mammals to infectious agents have revealed that members of the hsp60 and hsp 70 family are highly immunodominant. Given their high conservation during evolution this was surprising, because of the apparent risk of triggering of autoimmunity and autoimmune disease during the defense of a mammal against infection. However, detailed studies of the immune responses to HSP in models of autoimmune diseases in animals resulted in a change of the view that autoimmunity necessarily leads to autoimmune disease. It has been found that modulation of autoimmunity to HSP is one way to prevent autoimmune disease. At least in some cases even treatment of autoimmune diseases by immunization with heat shock protein appears feasible. This was shown in adjuvant arthritis in Lewis rats and insulin dependent diabetes in NOD mice. Hsp60 and hsp70 are ubiquitous proteins. Their involvement in regulatory loops of autoimmunity may serve as basis for the development of strategies, to prevent and/or treat autoimmune diseases even without knowledge of the causative (auto-)antigen.

Effects of the cytokine synthesis inhibitor CGP 47969A on nitric oxide production by lipopolysaccharide-stimulated J774A.1 macrophages

CGP 47969A is a novel inhibitor of the biosynthesis of interleukin-1 and other cytokines, being developed as an anti-arthritic. The effect of the compound on lipopolysaccharide (LPS; 1 microgram/ml) stimulated nitric oxide (NO) production by the mouse macrophage cell line, J774A.1, was examined in the present study. CGP 47969A inhibited NO production in a concentration-dependent fashion (0.1-10 microM; IC50 = 2 microM) in a 24 h assay. Dexamethasone (Dex), which inhibits cytokine and inducible nitric oxide synthase (iNOS) gene transcription, and N-methyl arginine (NMA), a substrate analogue inhibitor of NOS activity, also inhibited NO production in this assay system with IC50 values of approximately 5 nM and 100 microM, respectively. When iNOS expression was induced by LPS for 24 h, CGP 47969A and Dex did not inhibit NO production, whereas NMA retained activity (IC50 = 40 microM). In time course experiments, CGP 47969A (10 microM) or Dex (1 microM) were added to J774A.1 cultures at t = 0, 1, 3 or 6 h after LPS. Dex inhibited NO production by 86%, 57%, 35% and 15% at these time points, while CGP 47969A inhibited by 90%, 91%, 89% and 76%. Taken together, the results indicate that CGP 47969A inhibits NO production by an effect similar to the inhibitory effect on cytokine production rather than by inhibition of iNOS enzyme activity per se or iNOS gene expression. The ability of CGP 47969A to inhibit cytokine and NO production may explain its efficacy in animal models of arthritis.

A mutational analysis of receptor binding sites of interleukin-1 beta: differences in binding of human interleukin-1 beta muteins to human and mouse receptors

The 3-D crystal structure of interleukin-1 beta (IL-1 beta) has been used to define its receptor binding surface by mutational analysis. The surface of IL-1 beta was probed by site-directed mutagenesis. A total of 27 different IL-1 beta muteins were constructed, purified and analyzed. Receptor binding measurements on mouse and human cell lines were performed to identify receptor affinities. IL-1 beta muteins with modified receptor affinity were evaluated for structural integrity by CD spectroscopy or X-ray crystallography. Changes in six surface loops, as well as in the C- and N-termini, yielded muteins with lower binding affinities. Two muteins with intact binding affinities showed 10- to 100-fold reduced biological activity. The surface region involved in receptor binding constitutes a discontinuous area of approximately 1000 A2 formed by discontinuous polypeptide chain stretches. Based on these results, a subdivision into two distinct local areas is proposed. Differences in receptor binding affinities for human and mouse receptors have been observed for some muteins, but not for wild-type IL-1 beta. This is the first time a difference in binding affinity of IL-1 beta muteins to human and mouse receptors has been demonstrated.

A constitutive 65 kDa chondrocyte protein as a target antigen in adjuvant arthritis in Lewis rats

The autoantigen in adjuvant arthritis in Lewis rats is still unknown despite the knowledge that the 65 kDa mycobacterial heat-shock protein (hsp) is involved in the disease process. T cells and antibodies obtained from rats with adjuvant arthritis respond to chondrocyte membrane antigen(s). In Western blots a 65 kDa chondrocyte membrane protein (CH65) is stained by sera from arthritic rats. In addition, spleen cells from rats with adjuvant arthritis proliferate in vitro to chondrocyte membranes and CH65 as antigens. Furthermore, pretreatment of rats with CH65 or mycobacterial hsp65 but not human hsp60, induces a significant retardation of the onset of adjuvant arthritis in Lewis rats. The data suggest that CH65 is a potential autoantigen involved in the pathogenesis of adjuvant arthritis in Lewis rats.

Interleukin-8 is a cyclosporin A binding protein

Inflammatory immune reactions occur during transplant rejections and autoimmune diseases. Such reactions are mediated by cytokines, including interleukin-8 (IL-8). Cyclosporin A (CsA) exerts immunosuppressive activities by binding to immunoregulatory proteins termed cyclophilins. The anti-inflammatory effects of CsA are still not fully understood. Searching for novel neutrophil-activating proteins, we observed that an antiserum against human recombinant Interleukin-8 (IL-8) cross-reacted with cyclophilins in Western blots. Furthermore, native IL-8 was found to specifically bind CsA, whereas biologically inactive analogs of CsA were not bound by IL-8. Putative binding sites for CsA on IL-8 could be identified on the basis of structural similarities between IL-8 and cyclophilin. However, IL-8 lacks peptidyl-prolyl-isomerase (PPlase) enzyme activity, which is regarded as a characteristic of cyclophilins. We conclude that the specific binding of CsA to IL-8 may explain some of the anti-inflammatory effects of CsA. IL-8 may be a novel member of the cyclophilins lacking PPlase activity.

Heat shock proteins in autoimmune disease. From causative antigen to specific therapy?

Heat shock proteins (hsp) are highly conserved from bacteria to man. Bacterial hsp, with approximate molecular weights of 60 kDa (hsp60), are immunodominant antigens that are immunologically cross-reactive with their mammalian counterparts. Hsp molecules are therefore useful in studies of fundamental questions concerning immune responses to foreign as opposed to self antigens. The finding that immune responses to hsp are associated with both experimentally-induced and spontaneous autoimmune diseases in animals has prompted intensive research to assess the role of bacterial hsp as the etiological agents involved in the development of autoimmune diseases. Recent evidence from animal models of autoimmune disease has clearly demonstrated the involvement of hsp in both the pathogenesis and the immunoregulation of autoimmune diseases. Studies with arthritogenic and diabetogenic T cell clones have identified immunogenic epitopes of hsp. These have been shown to ameliorate adjuvant arthritis in Lewis rats, and insulin-dependent diabetes mellitus (IDDM) in non-obese diabetic (NOD) mice. Such studies may have important therapeutic implications for the future treatment of human autoimmune disease.

Prevention of adjuvant arthritis in rats by a nonapeptide from the 65-kD mycobacterial heat shock protein: specificity and mechanism

In a previous study we have shown that Lewis rats were completely protected from adjuvant arthritis by pretreatment with a nonapeptide (residues 180-188) of the 65-kD mycobacterial heat shock protein. Here we address questions of specificity and mechanism(s) of protection. We demonstrate that complete protection against adjuvant arthritis can only be achieved by pre-immunization with the nonapeptide, while pretreatment with either the octapeptide (residues 181-188) of the 65-kD heat shock protein or unrelated immunogenic peptides failed to affect adjuvant arthritis. Interestingly, pretreatment with the nonapeptide of the 65-kD heat shock protein did not protect Lewis rats from type II collagen-induced arthritis. These results demonstrate that protection is both epitope and disease specific. Co-injection of the nonapeptide with mycobacterial antigen even at a weight ratio of 5:1 (nonapeptide:mycobacteria) failed to influence the disease, suggesting that the role of the nonapeptide is not as a 'blocking peptide'. T cells from rats immunized with nonapeptide respond to the nonapeptide as well as to mycobacteria in vitro, and adoptively transfer protection to naive recipients. The data indicate that the nonapeptide-induced protection may result from a T cell-mediated specific suppression.

Prevention of adjuvant arthritis in rats by a nonapeptide from the 65-kD mycobacterial heat-shock protein

Adjuvant arthritis in Lewis rats is a model of T cell-mediated autoimmune arthritis resembling human rheumatoid arthritis. A nonapeptide from the 65-kD heat-shock protein of Mycobacterium bovis BCG, amino acid sequence 180-188, has been described to carry the dominant immunogenic epitope(s) for both arthritis-protective and arthritogenic T cell clones. Here we demonstrate that immunizations with the synthetic nonapeptide completely protected rats against adjuvant arthritis induced by M. tuberculosis. Interestingly, deletion of the N-terminal threonine of the nonapeptide resulted in loss of the protective activity. Pretreatments with the nonapeptide resulted in an immune response to the nonapeptide and to M. tuberculosis. After immunizations with the synthetic nonapeptide, only low titres of nonapeptide-specific antibodies were produced, whereas a significant cellular immune response to the nonapeptide was observed. In addition, the protection was transferable to naive rats by spleen T cells. These findings document the requirement of a T cell-specific immune response to the dominant epitope of the 65-kD mycobacterial heat-shock protein for the protection against adjuvant arthritis and suggest the feasibility of immune intervention in autoimmune arthritis through the use of synthetic peptides.

Treatment of adjuvant arthritis in rats: vaccination potential of a synthetic nonapeptide from the 65 kDa heat shock protein of mycobacteria

Adjuvant arthritis induced by mycobacteria in rats is a widely used model of chronic arthritis. A previously described nonapeptide (Thr-Phe-Gly-Leu-Gln-Leu-Glu-Leu-Thr, amino acid sequence 180-188) from the recombinant 65 kDa heat shock protein of Mycobacterium bovis BCG, which was found to contain a T-cell epitope recognized by both arthritogenic and protective T-cell clones in vitro, has been investigated for its vaccination and therapeutic potential in adjuvant arthritis in rats. The nonapeptide was found not to be arthritogenic, although the T cells from nonapeptide immunized rats cross-react in vitro with mycobacterial antigens. Intraperitoneal administration of 0.1 mg nonapeptide in oil at day -20 or days -2, -1 and 0, resulted in a marked reduction of incidence and severity of adjuvant arthritis. The disease process and severity were also influenced by therapeutic treatment with 0.1 mg nonapeptide injected intraperitoneally at days 7 to 10. Interestingly, subplantar or intravenous application of the nonapeptide had no influence on the disease process. Deletion of the N-terminal threonine led to complete loss of in vivo activity of the nonapeptide.

Interactions of micromolar concentrations of fluoride with Streptococcus rattus FA-1

Inhibition of the metabolic activities of bacteria by trace amounts of fluoride is manifested phenomenologically as changes in the pH gradient and/or the electrical potential between the cellular interior and the surrounding medium. These data were obtained from the intracellular/extracellular distribution of radioactivity labelled fluoride (18F), 5,5-dimethyloxazolidine-2,4-dione (14C), and tetraphenylphosphonium chloride (14C). When taken up from acidic media, trace concentrations of fluoride (1-100 microM) reduce the intracellular/extracellular pH gradient and affect the electrical potential across the cell membrane. The chromatographic fractionation of fluoride-charged bacterial homogenates showed that fluoride is attached to many proteins of the cytoplasm, the cell membrane, and to nonproteinaceous components of the cell wall. Lysozyme treatment synergistically affects the vulnerability of the bacteria to micromolar concentrations of fluoride.

Differential immunological response of patients with rheumatoid arthritis towards two different Epstein-Barr virus strains: inhibition of interleukin-1 release by the B95-8, but not the P3HR-1 virus strain

An abnormal immune response towards the Epstein-Barr virus (EBV) has been documented in patients with rheumatoid arthritis (RA). To investigate whether these findings are due to the transformation event caused by EBV, RA blood mononuclear cells and monocyte-enriched preparations were incubated with two different EBV strains: the transforming virus secreted by the cell line B95-8 and the virus released by the P3HR-1 cell line that is not able to transform due to a small deletion in the U2 region of the virus genome. Immunological response was determined by the production of interleukin-1 (IL-1) and tumor necrosis factor (TNF) using ELISA and bioassay systems. There was a striking difference in cytokine measurements with a strong inhibition of IL-1 and TNF production after incubation with the B95-8 virus, but not the P3HR-1 virus. These data indicate that the disturbed reaction of the immune system towards EBV is either dependent on the full transformation of B cells in RA patients or alternatively due to the secretion of a cytokine inhibitor by the B95-8 cell line.

Interleukin-1 enhances pain reflexes. Mediation through increased prostaglandin E2 levels

Interleukin-1 (IL-1) has been shown to induce inflammatory reactions in part through increased prostaglandin production. Prostaglandins of the E- and I-type sensitize nociceptors in peripheral tissues. We have therefore investigated the effect of IL-1 perfusion in the isolated rabbit ear, a model which allows the assessment of peripheral pain. Natural IL-1 from human monocytes, IL-1 from glioblastoma cells as well as recombinant IL-1 alpha or beta, increased the pain reflex induced by acetylcholine in a concentration dependent manner. The PGE2 levels were measured in the perfusate and were found to be enhanced more than 10-fold after the infusion of IL-1 alpha or IL-1 beta. This effect was paralleled by the enhanced pain reflexes and persisted for at least one hour after cessation of the IL-1 perfusion. Both the increased pain reflexes as well as the enhanced PGE2 levels were abolished by addition of the cyclooxygenase inhibitor diclofenac-Na (Voltaren) to the perfusion fluid. These results show that besides the numerous known physiological functions of IL-1, it may also play a role in peripheral pain sensations.

Delayed type hypersensitivity (DTH) to type II collagen (CII) in DBA-1 mice

Sensitization of DBA-1 mice with Type II collagen (CII) in complete Freund's adjuvant can cause polyarthritis. A possible link between CII-induced arthritis and delayed type hypersensitivity (DTH) has been suggested, so we decided to investigate the susceptibility of DBA-1 mice to CII induced DTH reactions. The mice were primed with a dose of 10 micrograms CII i.p. 4 days before challenging with 40 micrograms CII in the ear. Swelling was measured 48 h later and was found to be reproducible. Responsiveness to CII could be transferred with whole spleen cell populations from primed animals or with enriched spleen T cells, thus confirming the cellular nature of the reaction. Lymph node cells from CII/CFA footpad immunized animals were restimulated with CII in vitro. These cells were able to passively transfer DTH sensitivity in vivo and exhibited specificity for this antigen in vitro in proliferation assays.

A monoclonal antibody to a differentiation antigen present on mature human macrophages and absent from monocytes

A monoclonal antibody is described that has been generated in the mouse against cultured human blood monocytes/macrophages. The antibody, designated 25F9, belongs to the IgG1 subclass, detects antigens of m.w. 86,000, and does not react with freshly isolated blood monocytes but reacts with monocytes after 3 days of culture. The expression of the 25F9 antigen on macrophages increases with culture time. Furthermore, the antibody is negative on platelets, granulocytes, lymphocytes, and a large number of human cell lines except the two melanoma lines MeWo and Mel 57. In cryostat sections of normal human tissue (skin, lung, liver, thymus) and of inflammatory or neoplastic tissue (cutaneous lymphoma, eczema, BCG-granuloma, and melanoma), the antibody reacts with scattered macrophages in the dermis but not with epidermal Langerhans cells, with alveolar macrophages, with liver Kupffer cells, and with scattered macrophages in the cortex and medulla of thymus. In eczema, BCG-granuloma, and cutaneous lymphoma, only a few infiltrating macrophages were stained. On the other hand, a large number of macrophages and melanophages reacted positively in melanoma. In some cases melanoma cells also stained weakly positive. Thus, the antibody detects a differentiation antigen preferentially expressed on mature, tissue-fixed macrophages and absent from blood monocytes.