Autoantibodies are highly prevalent in non-SARS-CoV-2 respiratory infections and critical illness

The widespread presence of autoantibodies in acute infection with SARS-CoV-2 is increasingly recognized, but the prevalence of autoantibodies in non-SARS-CoV-2 infections and critical illness has not yet been reported. We profiled IgG autoantibodies in 267 patients from 5 independent cohorts with non-SARS-CoV-2 viral, bacterial, and noninfectious critical illness. Serum samples were screened using Luminex arrays that included 58 cytokines and 55 autoantigens, many of which are associated with connective tissue diseases (CTDs). Samples positive for anti-cytokine antibodies were tested for receptor blocking activity using cell-based functional assays. Anti-cytokine antibodies were identified in > 50% of patients across all 5 acutely ill cohorts. In critically ill patients, anti-cytokine antibodies were far more common in infected versus uninfected patients. In cell-based functional assays, 11 of 39 samples positive for select anti-cytokine antibodies displayed receptor blocking activity against surface receptors for Type I IFN, GM-CSF, and IL-6. Autoantibodies against CTD-associated autoantigens were also commonly observed, including newly detected antibodies that emerged in longitudinal samples. These findings demonstrate that anti-cytokine and autoantibodies are common across different viral and nonviral infections and range in severity of illness.

Is conservative management of the indeterminate thyroid nodule [Thy3f or Bethesda category IV] safe?

PURPOSE

The histological diagnosis after diagnostic thyroidectomy for indeterminate thyroid nodules is often non-malignant and some cancers detected are considered 'indolent'. The safety and effectiveness of conservative management in these patients are unclear. The aim of this study was to determine the safety of conservative management of indeterminate thyroid nodules and to explore association between clinical features and pathology in patients undergoing surgery.

METHODS

This is a retrospective cohort study of patients presenting to a single centre over a 4-year period (2013-2016) with thyroid nodules that were considered indeterminate (thy3f in the UK RCPath classification) on cytology. Demographic data, ultrasound features, follow-up details (in those undergoing conservative management) and histology details (in those undergoing surgery) were collected.

RESULTS

Of 164 patients that had Thy3f cytology, 34 were initially managed conservatively; however, 4 of these eventually had surgery (due to patient preference). No patient on conservative management had significant disease progression on ultrasound at a median (interquartile range) of 27 (16-40) months. Of the 134 patients that underwent surgery, 26 had thyroid malignancy. The BTA 'U' classification, gender and age (> 55) were not associated with malignancy in these nodules, but larger nodules (> 40 mm) were more likely to be malignant (p = 0.042).

CONCLUSIONS

Conservative management of indeterminate (Thy3f or Bethesda stage IV) thyroid nodules is safe in the short term and may be indicated in selected cases after appropriate discussion of risks and benefits of surgery.

Immunoglobulin G4-related disease in a dog

Immunoglobulin G4-related disease (IgG4-RD), which affects many organ systems, has been recognized as a distinct clinical entity in human medicine for just over a decade but has not been previously identified in dogs. In humans, IgG4-RD is characterized by diffuse IgG4-positive lymphoplasmacytic infiltrates that commonly lead to increased serum concentrations of IgG4 and IgE, peripheral eosinophilia, tumorous swellings that often include the parotid salivary glands, obliterative phlebitis, and extensive fibrosis. Herein we describe the diagnosis, clinical progression, and successful treatment of IgG4-RD in an 8-year-old female spayed Husky mixed breed dog. Immunoglobulin G4-related disease should be considered as a differential diagnosis for dogs with vague clinical signs, lymphoplasmacytic swellings, restricted polyclonal gammopathy, eosinophilia or some combination of these findings.

Smoking Predicting Physical Activity in an Aging America

OBJECTIVES

Tobacco smoking and physical inactivity are among leading behavioral risk factors for ill health in older adults. This study considers how smoking is associated with physical activity.

DESIGN

Using a Life-Course model, data are analyzed regarding this relationship, controlling for, and interacted with, life-course and other factors. Daily smokers and sometimes smokers were hypothesized to engage in less leisure-time physical activity than those who never smoked, while those who stopped smoking were expected to do more than never smokers. Analyses were performed using SAS-Callable SUDAAN.

SETTING AND PARTICIPANTS

Secondary data from ten years of a national sample of adults aged 18 and over of the National Health Interview Survey, 2001-2010, are used (N = 264,945, missing data excluded, of 282,313 total cases).

MEASUREMENTS

Daily smokers, occasional smokers, and smoking quitters are compared to never smokers with regard to requisite physical activity (150 minutes per week of moderate, 100 of vigorous, and/or 50 of strengthening activity). Life-course measures include birth cohorts, age, and year of survey, as well as gender, race/ethnicity, and education.

RESULTS

Overall, hypotheses are supported regarding daily smokers and quitters; but the hypothesis is strongly rejected among sometimes smokers, who are much more likely to do requisite physical activity. Findings differ by age, sometimes smokers age 65 and over being less likely to do physical activity. Findings among all men are similar to the overall findings, while those among all women are similar to those for older respondents. Associations of smoking status with physical activity vary greatly by race/ethnicity.

CONCLUSIONS

Daily smokers may be most in need of both smoking cessation and leisure-time physical activity interventions. Smoking-cessation efforts may pay greater physical activity benefits among women and the aged, while smoking-reduction efforts may provide better outcomes among men. Smoking reduction efforts may pay more exercise benefits among African-Americans and Hispanics.

Atypical Morphology and Disparate Speciation in a Case of Feline Cryptococcosis

A 6-year-old, spayed female cat was presented with acute respiratory signs and pleural effusion. Computed tomography scan revealed a large, lobulated mass effect in the ventral right hemithorax with concurrent sternal lymphadenopathy. A cytologic sample of the mass contained pyogranulomatous inflammation, necrotic material, and abundant yeast structures that lacked a distinct capsule and demonstrated rare pseudohyphal forms. Fungal culture and biochemical testing identified the yeast as Cryptococcus albidus, with susceptibility to all antifungal agents tested. However, subsequent 18S PCR identified 99% homology with a strain of Cryptococcus neoformans and only 92% homology with C. albidus. The patient responded well to fluconazole therapy unlike the only known previous report of C. albidus in a cat. The unusual cytologic morphology in this case underscores the need for ancillary testing apart from microscopy for fungal identification. Though C. albidus should be considered as a potential feline pathogen, confirmation with PCR is recommended when such rare non-neoformans species are encountered.

Evaluation of the biological differences of canine and human factor VIII in gene delivery: implications in human hemophilia treatment

The canine is the most important large animal model for testing novel hemophilia A (HA) treatment. It is often necessary to use canine factor VIII (cFIII) gene or protein for the evaluation of HA treatment in the canine model. However, different biological properties between cFVIII and human FVIII (hFVIII) indicated that the development of novel HA treatment may require careful characterization of non-human FVIII. To investigate whether the data obtained using cFVIII can translate to HA treatment in human, we analyzed the differential biological properties of canine heavy chain (cHC) and light chain (cLC) by comparing with human heavy chain (hHC) and light chain (hLC). The secretion of cHC was 5-30-fold higher than hHC, with or without light chains (LCs). cHC+hLC group exhibited ~18-fold increase in coagulation activity compared with hHC+hLC delivery by recombinant adeno-associated viral vectors. Unlike hHC, the secretion of cHC was independent of LCs. cLC improves the specific activity of FVIII by two- to threefold compared with hLC. Moreover, the cLC, but not cHC, contributes to the higher stability of cFVIII. Our results suggested that the cFVIII expression results in the canine model should be interpreted with caution as the cHC secreted more efficiently than hHC and cLC exhibited a more active and stable phenotype than hLC.

High density micromass cultures of a human chondrocyte cell line: a reliable assay system to reveal the modulatory functions of pharmacological agents

Osteoarthritis is a highly prevalent and disabling disease for which we do not have a cure. The identification of suitable molecular targets is hindered by the lack of standardized, reproducible and convenient screening assays. Following extensive comparisons of a number of chondrocytic cell lines, culture conditions, and readouts, we have optimized an assay utilizing C-28/I2, a chondrocytic cell line cultured in high-density micromasses. Utilizing molecules with known effects on cartilage (e.g. IL-1β, TGFβ1, BMP-2), we have exploited this improved protocol to (i) evoke responses characteristic of primary chondrocytes; (ii) assess the pharmacodynamics of gene over-expression using non-viral expression vectors; (iii) establish the response profiles of known pharmacological treatments; and (iv) investigate their mechanisms of action. These data indicate that we have established a medium-throughput methodology for studying chondrocyte-specific cellular and molecular responses (from gene expression to rapid quantitative measurement of sulfated glycosaminoglycans by Alcian blue staining) that may enable the discovery of novel therapeutics for pharmacological modulation of chondrocyte activation in osteoarthritis.

THE REACTION OF NEREIS VIRENS TO UNILATERAL TENSION OF ITS MUSCULATURE

1. The anterior segments of Nereis are oriented reflexly by passive unilateral tension of the posterior musculature. 2. The afferent impulses of the homostrophic reflex rise from any part of the worm and are conducted forward by way of the ventral nerve cord. 3. The efferent impulses flow out from the brain and anterior two or three ventral ganglia. 4. The homostrophic reflex may be partially or wholly masked by stereotropism.

LUMINESCENCE IN MNEMIOPSIS

1. In the dark adapted Mnemiopsis, mechanical stimulation causes luminescence along the eight rows of paddle plates. The tactile receptors for this reaction lie only in the paddle plate rows, and are connected only longitudinally along these rows. 2. The tactile receptors for ciliary and muscular movement are distributed generally over the surface and are connected by a nerve net. 3. Luminescence may occur at 3°C. provided the animal has been kept sufficiently long at that temperature. Ciliary action goes on at – 0.6°C. 4. Luminescent paper made by spreading the luminescent secretion of Mnemiopsis on filter paper, yields the following effects. The paper shows luminescence in solutions of K₂SO₄, KCl, MgSO₄, SrCl₂, CaCl₂; no luminescence in NaCl, MgCl₂. Changes in pH value of salt solutions between pH 6 and 8 do not affect the phenomenon. Illumination of the paper with strong light for longer time than necessary to suppress luminescence in the living animal has no effect on the subsequent luminescence of the paper. Hence in the animal, light affects luminescence through the photoreceptor system; the nervous system carries the impulse to the luminescent organs. 5. The power of luminescence of the animal is suppressed by sufficiently intense light, the relation between the intensity and the time requisite being expressed by the equation for the Bunsen-Roscoe photochemical law, namely, I · t = K. 6. It is suggested that the reaction scheme involved in luminescence is of the following form See PDF for Equation in which A is the luminescent substance in the resting, dark adapted animal, L is the light-giving decomposition product, and D is a product which does not yield light. 7. The luminescent substance receives double innervation and the character of the decomposition is determined by the type of nerve fiber stimulated.

NOTE ON THE EXCITATION AND INHIBITION OF LUMINESCENCE IN BEROE

1. The ions of Ca and K condition general luminescence, and are therefore necessary to the conduction of the impulse. 2. In van't Hoff's solution from which Mg is omitted, Berœ shows hyperirritability with respect to luminescence. This is the result of the action of Ca and K ions unantagonized by Mg. 3. The luminescent material spread on filter paper does not show luminescence in sea water, NaCl, MgCl₂, or saccharose solutions isotonic with sea water. In solutions of CaCl₂, SrCl₂, BaCl₂, KCl, and K₂SO₄ the indicator paper glows with a bright luminescence. 4. In dark adapted Berœ, luminescence is inhibited by a certain quantity of light. This quantity has an average value of 57,285 meter-candle-minutes, which is twelve times the value given by Mnemiopsis.

THE NERVOUS MECHANISM OF COORDINATION IN THE CRINOID, ANTEDON ROSACEUS

1. Stimulation causes Antedon to swim by means of alternate oral bending and dorsal stroke of the arms. Two arms of a given ray move alternately so that while one is executing the aboral stroke its mate is flexing ventrally. This implies reciprocal inhibition. 2. Recriprocal inhibition between the two arms of an isolated ray can be abolished by the use of either strychnine or nicotine. 3. Coordination between the rays is referable to the conducting properties of the nervous pentagon which connects the five rays. In this system an impulse loses in effectiveness as it passes from the point of origin. 4. When Antedon is made to rest oral face down on the floor of an aquarium, oral flexion of all the rays, swimming movements, and righting result. Antedon is therefore negatively stereotropic with reference to its ventral side. 5. Excitation of the dorsal cirri results in aboral bending of all the rays. Stimulation of the cirri inhibits ventral flexion to the extent of preventing righting movements while on the other hand stimulation of the ventral surface inhibits the grasp reflex of the cirri. Thus oral and aboral sides of Antedon exhibit dynamic symmetry although structurally dissimilar.

GALVANIC STIMULATION OF LUMINESCENCE IN PELAGIA NOCTILUCA

1. Pelagia noctiluca responds to galvanic stimulation by a luminescent glow at the anode. If placed near the cathode a secondary glow occurs also on the cathodal side. 2. The luminescent slime of Pelagia when subjected to the galvanic current glows around the cathode. This is referred partly to the movement of hydrogen bubbles, but in the main to the alkali formed at the cathode. 3. The cause of galvanic stimulation in Pelagia is ionic. (1) Anodal stimulation is referred to the blocking of positive ions by the tissue on that side. (2) Cathodal stimulation, when the animal lies near the cathode, is due to the diffusion of alkali outward from a region of high concentration (the cathode). 4. Only the margin of the bell is excited to luminescence by the galvanic current. It is therefore concluded that nervous elements are the seat of excitation. 5. Luminescence is not a result of muscular contraction, since K ion causes relaxation of musculature but a continuous luminescent glow in Pelagia. The galvanic current causes pulsations of the bell (contraction and relaxation of the musculature) but a continuous glow.

THE RESPONSE OF POPILLIA JAPONICA TO LIGHT AND THE WEBER-FECHNER LAW

Light and a temperature above 23°C. are necessary for the activity of Popillia. The effect of light as indicated by the rate of locomotor response is related to light intensity according to Fechner's expression of Weber's law.

MUSCLE TENSION AND REFLEXES IN THE EARTHWORM

1. By the use of preparations of earthworm in which the cutaneous receptors have been anesthetized with a solution of M/8 MgCl₂, it is shown that peristalsis can be initiated by tension alone. 2. The receptors of the tension reflex are the intermyal sensory cells of the ventral region of the body wall. 3. It is concluded that Straub obtained the tension reflex because his preparations contained the intermyal receptors; Budington was unable to observe the tension reflex in any preparation from which the intermyal receptors had been removed. 4. Intermyal receptors are the receptors of the following reaction: Passive unilateral tension of the posterior part of an earthworm induces active homolateral tension of the musculature of the anterior segments, and results in the course of progress being brought into line with the enforced orientation of the tail. This reaction is termed the homostrophic reflex. 5. The receptors for the reaction are distributed throughout the entire length of the worm, the effectors are limited to the anterior 15 to 20 segments. The impulse is conducted by the ventral nerve cord. 6. The interaction of the homostrophic reflex and tropisms is considered.

HOMOSTROPHIC REFLEX AND STEREOTROPISM IN DIPLOPODS

1. With suitable arthropods, such as the diplopods, it can be shown that body orientation following passive unilateral tension involves the homostrophic reflex. The phenomenon is exhibited when the animal is quiescent and during forward locomotion, but nothing of the sort appears in backward locomotion. 2. Receptors for the homostrophic reflex are in the body wall and are distributed throughout the length of the animal. 3. The effector nerves take their origin from the ganglia of the head alone. 4. The diplopods are stereotropic, the head turning toward the side in contact with a solid surface only as long as some part of the body maintains contact. Under suitable conditions stereotropism may mask the homostrophic reflex. 5. When a diplopod is in contact with two lateral surfaces of equal extent the path upon emergence is a straight one, conforming to the law of the parallelogram of forces.

STEREOTROPISM AS A FUNCTION OF NEUROMUSCULAR ORGANIZATION

From what has been said concerning the neuromuscular organization of the Asterias ray, it is possible to arrive at certain definite conclusions regarding the nature of the stereotropism of that organ. The righting movements from the start are not haphazard; i.e., they cannot be explained on any hypothesis of "trial and error." The excitation of the sensory cells of the dorsal sheath initiates dorsal flexure of the ray. This movement makes it possible for the tube feet of the tip to touch bottom and start the vigorous action which follows and completes the righting If the "feelers" by chance touch bottom they initiate the reaction de novo. As to the remaining phases, the stereotropic reaction of the ray is referable to the high degree of surface sensitivity of the tube feet disks and the propagation of excitatory and inhibitory impulses, resulting from stimulation, along appropriate paths to the muscles of the ray. In this respect the tube feet may be regarded as playing a role similar to that of tropistic receptors in general. That is, unequal stimulation of the receptors causes a corresponding inequality of tone or of contraction in the musculature which ultimately results in an equilibrium of orientation to the factor involved. It is evident that as a mechanism for righting stereotropism differs in one important respect from other tropisms. The latter depend for their operation upon unilateral effects in organisms which are dynamically bilaterally symmetrical. In stereotropism the sensitivity of the organism is not distributed in bilaterally symmetrical fashion. As a rule only the ventral side is stereosensitive; i.e., the sensitivity is unilaterally distributed. There is a tropistic action in such cases because of the fact that when the sensitive surface is only partially stimulated an unequal contraction of the musculature follows and this as a result brings the sensitive surface into such a position that it is all equally stimulated. Equal muscle tone follows and the organism is in equilibrium with its environment.

THE FUNCTION OF THE BRAIN IN LOCOMOTION OF THE POLYCLAD WORM, YUNGIA AURANTIACA

Coordinated swimming movements in Yungia are not dependent upon the presence of the brain. The neuromuscular mechanism necessary for spontaneous movement and swimming is complete in the body of the animal apart from the brain. Normally this mechanism is set in motion by sensory stimulation arriving by way of the brain. The latter is a region of low threshold and acts as an amplifier by sending the impulses into a great number of channels. When the head is cut off these connections with the sensorium are broken, consequently peripheral stimulation does not have its usual effect. If, however, the motor nerves are stimulated directly as by mechanical stimulation of the median anterior region, then swimming movements result. Also if the threshold of the entire nervous mechanism is lowered by phenol or by an increase in the ion ratios See PDF for Equation and See PDF for Equation then again peripheral stimulation throws the neuromuscular mechanism into activity and swimming movements result.

THE SELECTIVE ACTION OF NICOTINE ON THE CENTRAL NERVOUS SYSTEM OF THE SQUID, LOLIGO PEALII

1. In specimens of freshly hatched squid, Loligo pealii, nicotine acts upon the cerebral ganglia alone. 2. After 1 minute in the nicotine solution 1:500,000, the latent period for the mantle spasm is independent of the time spent in the solution. 3. The mantle spasm is conditioned by a chemical reaction, since the temperature coefficient of the process has a magnitude of about 2.8. 4. The velocity of the process which brings about the mantle spasm varies as the cube root of the concentration of the nicotine.

REVERSAL OF REACTION BY MEANS OF STRYCHNINE IN PLANARIANS AND STARFISH

Two cases have been described, that of the marine planarian Bdelloura and that of the starfish Asterias forbesii, in which strychnine reverses reciprocal inhibition. These facts indicate that the nervous systems of these invertebrates function in a manner similar to those of the earthworm and vertebrates. Moreover, it would seem that strychnine acts upon some chemical component of the neuron which is always present in synaptic structures but which also occurs in the simpler neurons of lower forms. The fact that strychnine is without this characteristic effect on such forms as medusa and sea anemone, indicates that the nervous systems of the starfish and planarian have chemical affinities with the vertebrates which the cœlenterates do not possess.

THE RESPIRATORY RATE OF THE SCIATIC NERVE OF THE FROG IN REST AND ACTIVITY

1. With the indicator method of Haas, the rates of carbon dioxide production have been measured in the case of the sciatic nerve, various parts of the brain, and the sartorius muscle of the frog. The rate of respiration of the sciatic nerve is from 10 to 30 per cent of that of the other tissues, varying somewhat with the individual. 2. Stimulation of the sciatic nerve with induction shocks sufficient to induce tetanus of the muscle does not increase the output of carbon dioxide from the sciatic nerve, even if continued as long as 30 minutes. Sartorius muscle used as a control showed a marked increase in carbon dioxide production upon relaxation after contraction resulting from such stimulation. 3. These facts indicate that the nerve impulse does not depend upon processes leading to the production of carbon dioxide.

Accuracy and reproducibility of conformal radiotherapy using data from a randomised controlled trial of conformal radiotherapy in prostate cancer (MRC RT01, ISRCTN47772397)

Aims

The MRC RT01 trial used conformal radiotherapy to the prostate, a method that reduces the volume of normal tissue treated by 40–50%. Because of the risk of geographical miss, the trial used portal imaging to examine whether treatment delivery was within the required accuracy.

Material and methods

In total, 843 patients were randomly assigned to receive 64 Gy in 32 fractions over 6.5 weeks or 74 Gy in 37 fractions over 7.5 weeks. Field displacements and corrections were recorded for all imaged fractions. Displacement trends and their association with time, disease and treatment set-up characteristics were examined using univariate and multivariate analyses. A Radiographer Trial Implementation Group (RTIG) was set up to inform the quality assurance process and to promote the development of best practice.

Results

Treatment isocentre positioning was within 5 mm in every direction on 6238 (83%) of the 7535 fractions imaged. In total, 532 (81%) of 695 included patients had at least one ≥ 3mm displacement and 415 (63%) had at least one ≥ 5mm displacement. Univariate, multivariate and stepwise models of ≥ 5mm displacements showed an increased likelihood of displacement in weeks 1 and 2 with low melting point alloy (LMPA) blocks compared with multileaf collimators, film verification compared with electronic portal imaging (EPI) and increased number of fractions imaged. Except for LMPA, this was also seen for ≥ 5mm displacements in weeks 3–6.

Conclusions

Accurate conformal treatment was delivered. The use of EPI was associated with increased reported accuracy. The RTIG was a crucial part of the quality assurance process.

Developing ethical strategies to assist oncologists in seeking informed consent to cancer clinical trials

Randomised clinical trials have come to be regarded as the gold standard in treatment evaluation. However, many doctors see the discussion of a clinical trial as an intrusion into the doctor-patient relationship and find these discussions difficult to initiate. Detailed informed consent is now a requirement of patient participation in trials; however, it is known that patients commonly fail to understand and recall the information conveyed. These difficulties for doctors and patients raise questions about the ethical integrity of the informed consent process. In this study, we have developed a set of communication strategies underpinned by ethical, linguistic and psychological theory, designed to assist doctors in this difficult task. Initially, audiotape transcripts of 26 consultations in which 10 medical oncologists invited patients to participate in clinical trials were analysed by expert ethicists, linguists, oncologists and psychologists, using rigorous qualitative methodology. A subset of seven of these was subjected to detailed linguistic analysis. A strategies document was developed to address themes which emerged from these analyses. This document was presented to relevant expert stakeholders. Their feedback was incorporated into the final document. Four themes emerged from the analysis; (a) shared decision-making, (b) the sequence of moves in the consultation, (c) the type and clarity of the information provided and (d) disclosure of controversial information and coercion. Detailed strategies were developed to assist doctors to communicate in these areas. We have developed a set of ethical strategies which may assist health professionals in this difficult area. A training package based on these strategies is currently being evaluated in a multi-centre randomised controlled trial.

Problems with HIV/AIDS prevention, care and treatment in Togo, West Africa: professional caregivers' perspectives

This paper used accounts of professional caregivers to HIV/AIDS patients in Lomé, Togo, West Africa to explore the impacts of cultural, institutional and socio-economic factors in the fight against HIV/AIDS. Thirteen health professionals and 17 non-health professionals who work with people living with HIV/AIDS were interviewed in June and July 2002 in Lomé, Togo. The study found that, in Togo there are some cultural, socio-economic and institutional practices that put Togolese at risk of contracting HIV and complicate the care of those who become infected. People with HIV/AIDS face socio-economic, emotional and psychological battles as they attempt to deal with their physical health and the social reactions to such a stigmatizing disease. Thus, in order to contain the spread of HIV/AIDS, people living with HIV/AIDS, family caregivers, traditional healers as well as the public must be educated about the importance of preventing the disease and how each group can help achieve success in its control. Interventions in prevention and care should be designed with an awareness of these structural factors that contribute to the spread of AIDS and compromise the quality of care given to those who become infected.

Characterization of attenuated Renibacterium salmoninarum strains and their use as live vaccines

Two nutritionally mutant strains of Renibacterium salmoninarum (Rs) were isolated that grew on tryticase soy agar (Rs TSA1) or brain heart infusion agar (Rs BHI1). These 2 strains could be continuously cultured on these media, whereas typical R. salmoninarum would only grow on KDM-2 agar. We determined no other phenotypic difference that could be used to distinguish them from wild-type R. salmoninarum. Both strains were found to be avirulent when 5 x 10(6) bacteria were intraperitoneally (i.p.) injected into Atlantic salmon. Rs TSA1, Rs BHI1, and Rs MT-239 (a R. salmoninarum strain previously shown to be attenuated) were tested as live vaccines in 2 separate trials. The best protection was seen with Rs TSA1. Vaccinated Atlantic salmon had relative percent survival (RPS) of 50 at 74 d post-challenge in Trial 1 and 76 at 60 d post-challenge in Trial 2. In both trials, 100% of the control salmon died from bacterial kidney disease (BKD) (within 40 d for Trial 1 and 50 d for Trial 2) after i.p. challenge with 5 x 10(6) live cells of the virulent isolate Rs Margaree.

Resolution of inflammation

Acute inflammatory reactions, in contrast to chronic inflammatory reactions, are usually self-limiting and resolve. We have investigated the resolving phase of a number of immune and non-immune inflammatory reactions induced in the pleural cavity of rats. COX-2 is expressed during resolution of these models. Using carrageenan pleurisy, we showed that this enzyme has a proinflammatory role as the reaction develops but an antiinflammatory role as the lesion resolves. This antiinflammatory role is associated with production of cyclopentenone prostaglandins and the absence of PGE2. Dual COX-1/COX-2 inhibitors or COX-2 inhibitors when given at the peak of the inflammatory response delay resolution, an effect reversed by replacing CyPGs into the pleural space. PGF2alpha like the CyPGs appears to have a role in resolving this reaction. Stress proteins are also induced in a variety of acute inflammatory models during resolution. Heme oxygenase-1 (HO-1) is one such protein so too are members of the hsp70 family. An inducer of HO-1 promotes resolution whereas an inhibitor is proinflammatory. In most cases it appears to be the macrophage that is the source of proteins necessary for resolution to occur. Understanding how proinflammatory pathways switch to the antiinflammatory pathways necessary for resolution to take place may eventually allow the exploitation of endogenous antiinflammatory pathways in the treatment of chronic inflammation.

Host cell invasion and intracellular residence by Aeromonas salmonicida: role of the S-layer

Virulent strains of the fish pathogen Aeromonas salmonicida, which have surface S-layers (S+), efficiently adhere to, enter, and survive within macrophages. Here we report that S+ bacteria were 10- to 20-fold more adherent to non-phagocytic fish cell lines than S-layer-negative (S-) mutants. When reconstituted with exogenous S-layers, these S- mutants regained adherence. As well, latex beads coated with purified S-layers were more adherent to fish cell lines than uncoated beads, or beads coated with disorganized S-layers, suggesting that purified S-layers were sufficient to mediate high levels of adherence, and that this process relied on S-layer structure. Gentamicin protection assays and electron microscopy indicated that both S+ and S- A. salmonicida invaded non-phagocytic fish cells. In addition, these fish cells were unable to internalize S-layer-coated beads, clearly suggesting that the S-layer is not an invasion factor. Lipopolysaccharide (which is partially exposed in S+ bacteria) appeared to mediate invasion. Surprisingly, A. salmonicida did not show net growth inside fish cells cultured in the presence of gentamicin, as determined by viable bacterial cell counts. On the contrary, bacterial viability sharply decreased after cell infection. We thus concluded that the S-layer is an adhesin that promotes but does not mediate invasion of non-phagocytic fish cell lines. These cell lines should prove useful in studies aimed at characterizing the invasion mechanisms of A. salmonicida, but of limited value in studying the intracellular residence and replication of this invasive bacterium in vitro.

Co-culture of Aeromonas salmonicida and host cells in intraperitoneal implants is associated with enhanced bacterial survival

An experimental procedure that we named "in vivo co-culture technology" allowed us to study the interactions between Aeromonas salmonicida and host cells, inside semipermeable chambers implanted in the peritoneal cavity of Atlantic salmon. Intraperitoneal implants containing bacteria and host cells, or bacteria and lysed cells, consistently yielded higher numbers of viable bacteria than implants containing bacteria only. Electron microscopy confirmed that 30 min after chamber inoculation, numerous bacteria were already internalized by exudate cells, and that at 3 h, destruction of these cells was evident. Thus, the rapid invasion and (or) the A. salmonicida-mediated lysis of host cells may constitute a survival strategy in vivo. The co-culture of bacteria with exudate peritoneal cells may be applicable to the in vivo study of other pathogens.

Heme oxygenase isoform expression in cellular and antibody-mediated models of acute inflammation in the rat

Heme oxygenase (HO) is the rate-limiting enzyme in the catabolism of heme to biliverdin, carbon monoxide (CO), and free iron. The enzyme exists as a constitutive isoform (HO-2) and an inducible isoform (HO-1), which is also a stress protein (HSP32). HO-1 has previously been shown to be associated with the resolution phase of a non-immune model of acute inflammation. In addition, elevation of the enzyme was markedly anti-inflammatory. In the present study, these observations have been extended to two pleural models of immune-driven inflammation in the rat, an immediate type III hypersensitivity (Arthus) reaction and a delayed type IV hypersensitivity reaction. Whilst these models have differing inflammatory mechanisms and time courses, they both showed HO activity to be maximal during the resolution phase. This activity was associated with increases in exudate bilirubin (a breakdown product of biliverdin) and increased expression of HO-1. Immunocytochemical analysis of inflammatory cell smears from the two models showed that HO-1 and HO-2 expression was restricted to mononuclear cells in the type IV hypersensitivity reaction, but included the polymorphonuclear cell population in the type III hypersensitivity reaction. Thus, irrespective of the pathogenesis of the lesion, evidence is accumulating to suggest that HO-1 has a universal role in the resolution of inflammation.

Heme oxygenase isoform expression in cellular and antibody-mediated models of acute inflammation in the rat

Heme oxygenase (HO) is the rate-limiting enzyme in the catabolism of heme to biliverdin, carbon monoxide (CO), and free iron. The enzyme exists as a constitutive isoform (HO-2) and an inducible isoform (HO-1), which is also a stress protein (HSP32). HO-1 has previously been shown to be associated with the resolution phase of a non-immune model of acute inflammation. In addition, elevation of the enzyme was markedly anti-inflammatory. In the present study, these observations have been extended to two pleural models of immune-driven inflammation in the rat, an immediate type III hypersensitivity (Arthus) reaction and a delayed type IV hypersensitivity reaction. Whilst these models have differing inflammatory mechanisms and time courses, they both showed HO activity to be maximal during the resolution phase. This activity was associated with increases in exudate bilirubin (a breakdown product of biliverdin) and increased expression of HO-1. Immunocytochemical analysis of inflammatory cell smears from the two models showed that HO-1 and HO-2 expression was restricted to mononuclear cells in the type IV hypersensitivity reaction, but included the polymorphonuclear cell population in the type III hypersensitivity reaction. Thus, irrespective of the pathogenesis of the lesion, evidence is accumulating to suggest that HO-1 has a universal role in the resolution of inflammation.

COX-1, COX-2, and COX-3 and the future treatment of chronic inflammatory disease

A new generation of non-steroidal anti-inflammatory drugs has been described that selectively targets the inducible isoform of cyclo-oxygenase, cyclo-oxygenase 2 (COX-2). This isoform is expressed at sites of inflammation, which has led to the speculation that its inhibition could provide all the benefits of current nonsteroidal anti-inflammatory drugs, but without their major side-effects on the gastrointestinal system (which are due to inhibition of COX-1). We have shown that COX-2 (identified by use of specific antibodies) is induced during the resolution of an inflammatory response, inhibition of COX-2 resulting in persistence of the inflammation due to the prevention of the synthesis of a range of anti-inflammatory prostanoids. We propose that there is a third isoform of this enzyme family, COX-3, a proposal that will have implication for the prescription of both existing and new generation anti-inflammatory drugs, and might represent a new therapeutic target.

Hyaluronan--a review of the recent patent literature

A review of patent literature surrounding the use of hyaluronan (HA) and its derivatives, or agents capable of modulating endogenous levels, is presented. Indications are many and varied and include arthritis, abnormal wound healing, neoplasia, prevention of surgical adhesions and dermatological disorders. In many cases, it is the physicochemical and biological properties of HA itself that have been exploited. For example, HA and/or its derivatives have been suggested as a synovial fluid replacement, a vehicle for topical application of drugs, a matrix for sustained drug release and a putative drug delivery system (targeting HA receptors at sites of pathology). In each of these examples, the lack of toxicity of HA and its biocompatability are important considerations.

Drug-induced cognitive impairment in the elderly

Elderly people are more likely than younger patients to develop cognitive impairment as a result of taking medications. This reflects age- and disease-associated changes in brain neurochemistry and drug handling. Delirium (acute confusional state) is the cognitive disturbance most clearly associated with drug toxicity, but dementia has also been reported. The aetiology of cognitive impairment is commonly multifactorial, and it may be difficult to firmly establish a causal role for an individual medication. In studies of elderly hospital patients, drugs have been reported as the cause of delirium in 11 to 30% of cases. Medication toxicity occurs in 2 to 12% of patients presenting with suspected dementia. In some cases CNS toxicity occurs in a dose-dependent manner, often as a result of interference with neurotransmitter function. Drug-induced delirium can also occur as an idiosyncratic complication. Finally, delirium may occur secondary to iatrogenic complications of drug use. Almost any drug can cause delirium, especially in a vulnerable patient. Impaired cholinergic neurotransmission has been implicated in the pathogenesis of delirium and of Alzheimer's disease. Anticholinergic medications are important causes of acute and chronic confusional states. Nevertheless, polypharmacy with anticholinergic compounds is common, especially in nursing home residents. Recent studies have suggested that the total burden of anticholinergic drugs may determine development of delirium rather than any single agent. Also, anticholinergic effects have been identified in many drugs other than those classically thought of as having major anticholinergic effects. Psychoactive drugs are important causes of delirium. Narcotic agents are among the most important causes of delirium in postoperative patients. Long-acting benzodiazepines are the commonest drugs to cause or exacerbate dementia. Delirium was a major complication of treatment with tricyclic antidepressants but seems less common with newer agents. Anticonvulsants can cause delirium and dementia. Drug-induced confusion with nonpsychoactive drugs is often idiosyncratic in nature, and the diagnosis is easily missed unless clinicians maintain a high index of suspicion. Histamine H2 receptor antagonists, cardiac medications such as digoxin and beta-blockers, corticosteroids, non-steroidal anti-inflammatory agents and antibiotics can all cause acute, and, less commonly, chronic confusion. Drug-induced confusion can be prevented by avoiding polypharmacy and adhering to the saying 'start low and go slow'. Special care is needed when prescribing for people with cognitive impairment. Early diagnosis of drug-induced confusion, and withdrawal of the offending agent or agents is essential.

Effects of hyaluronan on models of immediate and delayed hypersensitivity in the rat

Others have previously shown that superoxide dismutase conjugated with hyaluronan (HA) retains enzymic activity but is non-immunogenic. Whether HA could be widely used to prevent sensitisation to protein/polypeptide therapeutics is not known. In this study we investigated the effects of HA on bovine serum albumin (BSA) and methylated BSA pleural reactions in sensitised rats (active Arthus and delayed hypersensitivity reactions respectively) and on a reverse passive Arthus reaction in which rats received an intravenous injection of rabbit immunoglobulin and intrapleural challenge with goat anti rabbit immunoglobulin. HA suppressed the active Arthus and delayed hypersensitivity models when administered at the time of sensitisation but only the delayed hypersensitivity model at the time of intrapleural challenge. HA did not modulate the reverse passive Arthus reaction. The results show no evidence that simple mixing of HA with antigens masks antigenic determinants. However, HA appeared to have suppressive effects on both antibody and cell-mediated immune reactions. Therefore it may not be necessary to conjugate protein/polypeptide therapeutics to HA in order to prevent immune sensitisation.

Destruction of articular cartilage by alpha 2 macroglobulin elastase complexes: role in rheumatoid arthritis

OBJECTIVE

Neutrophil elastase accounts for the ability of some fresh rheumatoid synovial fluids to degrade cartilage matrix in vitro. The aim of this study was to determine if enzyme activity could result from depletion of synovial fluid inhibitors or protection of the enzyme from inhibition.

METHODS

The ability of synovial fluids to inhibit porcine pancreatic elastase was investigated together with chemical pretreatments capable of inactivating alpha 1 protease inhibitor (alpha 1PI) or preventing formation of alpha 2 macroglobulin (alpha 2M) elastase complexes. Subsequently, complexes of human neutrophil elastase with alpha 2M were prepared and applied to frozen sections of cartilage. Proteoglycan loss was quantified by alcian blue staining and scanning and integrating microdensitometry. Parallel studies were carried out using a low molecular weight chromogenic elastase substrate. The effects of alpha 1PI and SF on these systems were investigated. Finally, synovial fluids were subjected to gel filtration and the fractions assayed for elastase activity. High molecular weight fractions were pooled, concentrated, and tested for their ability to degrade cartilage sections.

RESULTS

All synovial fluids reduced the activity of porcine pancreatic elastase, the inhibition mainly being attributable to alpha 1PI, whereas remaining activity resulted from complexes of elastase with alpha 2M. Complexes of human neutrophil elastase with alpha 2M were shown to cause proteoglycan degradation in frozen sections of human articular cartilage. Alpha 1PI prevented alpha 2M elastase complexes from degrading cartilage but not the chromogenic substrate. The data suggested that alpha 1PI does not inhibit elastase bound to alpha 2M but sterically hinders the complex. However, only one of five synovial fluids was able to completely block the actions of alpha 2M elastase complexes against cartilage. Gel filtration of rheumatoid synovial fluids showed elastase and cartilage degrading activity to be associated with fractions that contained alpha 2M, and not with fractions expected to contain free enzyme.

CONCLUSIONS

The data suggest that synovial fluid alpha 2M elastase complexes can degrade cartilage matrix in rheumatoid arthritis.

Size is everything--large amounts of information are needed to overcome random effects in estimating direction and magnitude of treatment effects

Variability in patients' response to interventions in pain and other clinical settings is large. Many explanations such as trial methods, environment or culture have been proposed, but this paper sets out to show that the main cause of the variability may be random chance, and that if trials are small their estimate of magnitude of effect may be incorrect, simply because of the random play of chance. This is highly relevant to the questions of 'How large do trials have to be for statistical accuracy?' and 'How large do trials have to be for their results to be clinically valid?' The true underlying control event rate (CER) and experimental event rate (EER) were determined from single-dose acute pain analgesic trials in over 5000 patients. Trial group size required to obtain statistically significant and clinically relevant (0.95 probability of number-needed-to-treat within -/+0.5 of its true value) results were computed using these values. Ten thousand trials using these CER and EER values were simulated using varying group sizes to investigate the variation due to random chance alone. Most common analgesics have EERs in the range 0.4-0.6 and CER of about 0.19. With such efficacy, to have a 90% chance of obtaining a statistically significant result in the correct direction requires group sizes in the range 30-60. For clinical relevance nearly 500 patients are required in each group. Only with an extremely effective drug (EER > 0.8) will we be reasonably sure of obtaining a clinically relevant NNT with commonly used group sizes of around 40 patients per treatment arm. The simulated trials showed substantial variation in CER and EER, with the probability of obtaining the correct values improving as group size increased. We contend that much of the variability in control and experimental event rates is due to random chance alone. Single small trials are unlikely to be correct. If we want to be sure of getting correct (clinically relevant) results in clinical trials we must study more patients. Credible estimates of clinical efficacy are only likely to come from large trials or from pooling multiple trials of conventional (small) size.

Effects of diacerhein on granuloma induced cartilage breakdown in the mouse

OBJECTIVE

Diacerhein, an anti-osteoarthritic agent, was tested for its ability to suppress synthesis of proinflammatory cytokines in a model of granuloma-induced cartilage breakdown.

DESIGN

50 TO mice received a subcutaneous implant of cotton-wrapped rat femoral head cartilage for a period of 2 weeks. Animals (N = 10/group) were dosed daily with either 6 mg/kg p.o. diclofenac or diacetylrhein at 5, 15 or 50 mg/kg p.o. in 0.1.ml 1% gum tragacanth which served as a control. Implanted cartilages were assayed for glycosaminoglycan (GAG) and hydroxyproline content. The surrounding granulomas were assayed for interleukin-1 alpha (IL-1 alpha), tumour necrosis factor-alpha (TNF-alpha) and IL-6. Statistical analysis was by Mann-Whitney U test.

RESULTS

Diclofenac had no significant effect on GAG or hydroxyproline content of implanted cartilage or on granuloma cytokine concentrations. Diacerhein protected implanted cartilages against hydroxyproline loss, implanted control cartilages contained 220 micrograms hydroxyproline compared with diacerhein at 5, 15 and 50 mg/kg which produced a 21, 16 and 59% decrease in hydroxyproline loss compared with non-implanted controls (P < 0.05, 0.05 and 0.001) respectively. Diacerhein also protected against GAG loss at 5 mg/kg and 50 mg/kg, control cartilages contained 134 micrograms GAG compared with diacerhein at 5 mg/kg and 50 mg/kg which produced a 24 and 38% decrease in GAG loss respectively (P < 0.05 for both). Diacerhein significantly reduced granuloma interleukin-1 alpha content at 5 mg/kg (control level of 2.4 micrograms/ml reduced by 58%; P < 0.05), reduced TNF-alpha at 5 mg/kg and 15 mg/kg (reduced by 61%: P < 0.01 and 49%: P < 0.05 respectively; control level of 469 pg/ml) and reduced IL-6 at 15 mg/kg and 50 mg/kg (control level of 537 pg/ml reduced by 60 and 51%, respectively; P < 0.01 for both).

CONCLUSIONS

The mechanism of the chondroprotective effects of diacerhein is not understood but may be explained by a reduction in the concentrations of proinflammatory cytokines.

Oral dosing of rats with OM-89 results in the appearance of specific OM-89 antibodies of the IgG2a isotype: possible significance in the treatment of rheumatoid arthritis

OM-89 is a glycoprotein-rich extract of Escherichia coli shown to be effective in the treatment of rheumatoid arthritis (RA). It has been reported that oral dosing of animals results in the appearance of specific OM-89 antibodies. In the current study we have investigated some of the immunoglobulin isotypes that may be involved. OM-89 antibodies of IgG1, IgG2a and IgM isotypes were measured by ELISA in serum from rats dosed three times a week for 3 weeks at 4 or 40 mg kg(-1). The results showed a small but significant rise in IgM and a greater rise in IgG2a. The possibility that antigens within OM-89 (e.g. hsp65) may have homology with antigens involved in RA raises the possibility that OM-89 antibodies, particularly of the IgG2 class, may block pathogenic antigens from being recognized by T cells.

Single-patient data meta-analysis of 3453 postoperative patients: oral tramadol versus placebo, codeine and combination analgesics

The analgesic effectiveness and safety of oral tramadol were compared with standard analgesics using a meta-analysis of individual patient data from randomised controlled trials in patients with moderate or severe pain after surgery or dental extraction. Calculation of %maxTOTPAR from individual patient data, and the use of > 50%maxTOTPAR defined clinically acceptable pain relief. Number-needed-to-treat (NNT) for one patient to have > 50%maxTOTPAR compared with placebo was used to examine the effectiveness of different single oral doses of tramadol and comparator drugs. Eighteen randomised, double-blind, parallel-group single-dose trials with 3453 patients using categorical pain relief scales allowed the calculation of %maxTOTPAR. The use of > 50%maxTOTPAR was a sensitive measure to discriminate between analgesics. Tramadol and comparator drugs gave significantly more analgesia than placebo. In postsurgical pain tramadol 50, 100 and 150 mg had NNTs for > 50%maxTOTPAR of 7.1 (95% confidence intervals 4.6-18), 4.8 (3.4-8.2) and 2.4 (2.0-3.1), comparable with aspirin 650 mg plus codeine 60 mg (NNT 3.6 (2.5-6.3)) and acetaminophen 650 mg plus propoxyphene 100 mg (NNT 4.0 (3.0-5.7)). With the same dose of drug postsurgical patients had more pain relief than those having dental surgery. Tramadol showed a dose-response for analgesia in both postsurgical and dental pain patients. With the same dose of drug postsurgical pain patients had fewer adverse events than those having dental surgery. Adverse events (headache, nausea, vomiting, dizziness, somnolence) with tramadol 50 mg and 100 mg had a similar incidence to comparator drugs. There was a dose response with tramadol, tending towards higher incidences at higher doses. Single-patient meta-analysis using more than half pain relief provides a sensitive description of the analgesic properties of a drug, and NNT calculations allow comparisons to be made with standard analgesics. Absolute ranking of analgesic performance should be done separately for postsurgical and dental pain.

The cell surface of Aeromonas salmonicida determines in vitro survival in cultured brook trout (Salvelinus fontinalis) peritoneal macrophages

Aeromonas salmonicida strains phenotypically differing in their A-layer, lipopolysaccharide, and macrophage cytotoxicity were tested in vitro for survivability in brook trout (Salvelinus fontinalis) serum with or without antibodies, and in vivo following intraperitoneal injection. The ability of brook trout peritoneal macrophages to phagocytize and kill the different phenotypes was investigated in an in vitro assay. The virulent strain, A. salmonicida 80204, which has the full complement of known virulence factors, as well as the recently described macrophage cytotoxin, was resistant in vitro to both the bactericidal activity of normal and immune serum, and to brook trout peritoneal macrophages. A. salmonicida SS-70.1, which possesses the A-layer but lacks the cytotoxin, was resistant to the bactericidal activity of normal and immune serum but was avirulent and killed by macrophages. Phenotypes lacking the A-layer, regardless of whether or not they possessed the macrophage cytotoxin were avirulent, susceptible to normal and immune serum and the bactericidal activity of peritoneal macrophages. A. salmonicida virulence expression requires both the A-layer and the macrophage cytotoxin.

Impaired activity of protease inhibitors towards neutrophil elastase bound to human articular cartilage

OBJECTIVE

To investigate the effects of protease inhibitors on the ability of free and cartilage bound neutrophil elastase to degrade cartilage proteoglycan in vitro.

METHODS

Cryostat sections of human articular cartilage were used as substrate, and proteoglycan loss induced by free or cartilage bound elastase was quantified by alcian blue staining, followed by scanning and integrating microdensitometry.

RESULTS

High molecular mass protease inhibitors (alpha 1 protease inhibitor, alpha 2 macroglobulin, and soya bean trypsin inhibitor) and synovial fluid from patients with rheumatoid arthritis were effective in blocking proteoglycan loss from sections treated with free elastase, but their activity towards cartilage bound elastase was much reduced. In contrast, low molecular mass elastase inhibitors (N-methoxysuccinyl-Ala-Ala-Pro-Val chloromethyl ketone and ONO-5046 (N-[2-[4-(2,2-dimethylpropionyloxy) phenylsulphonylamino]benzoyl] amino-acetic acid) were effective against free and cartilage bound elastase.

CONCLUSION

The binding of elastase to cartilage appears to be a mechanism whereby the enzyme can remain active in the presence of high molecular mass protease inhibitors.

Use of time during body computed tomography scanning in a tertiary care teaching hospital: focus on patient throughput

RATIONALE AND OBJECTIVES

To control costs, it is increasingly important to make efficient use of imaging technology. We sought to determine and analyze the time required to complete each step of a body computed tomography (CT) scan, focusing on factors that influence patient throughput.

METHODS

Over 4 weeks, we prospectively monitored the time required for each step of a body CT scan (i.e., image time, check time, and clear time). Covariate data were collected by patient status: outpatient, inpatient, emergency department (ED), and intensive care unit (ICU); work shift; and radiologist training level (junior resident, senior resident, fellow, and attending). Technologists also predicted whether repeat images would be requested by the radiologist.

RESULTS

Three hundred eighty CT examinations were studied: 277 for outpatients, 90 for inpatients, 9 for ED patients, and 4 for ICU patients. The mean total examination time was 44.7 min (mean image time = 33.1 min, mean review time = 8.2 min, and mean clear time = 3.4 min), which did not differ significantly with patient status. A second opinion was sought from a consultant radiologist on the scans of 44 patients. Consultation was requested significantly more frequently (1) by junior residents than by senior residents or fellows and (2) for ED and ICU patients (22% and 50%, respectively) than in outpatients and inpatients (10% and 14%, respectively). Repeat images were obtained from 75 patients, and this was not significantly related to patient status, scan type, or radiologist training level. When the technologist predicted that no repeat images were needed, this prediction agreed with the radiologist in 86% of the cases. When the technologist predicted that repeat images were necessary, this prediction agreed with the radiologist in 56% of the cases.

CONCLUSION

Reviewing scans before the patient leaves the CT suite adds considerably to the total time required to complete a scan, particularly if junior residents review scans. If technologists obtain repeat images at their discretion, time would be saved.

Heme oxygenase: a novel target for the modulation of the inflammatory response

Chronic inflammatory diseases place a heavy social and economic burden on the resources of many nations, but the number of safe and effective treatments is limited. To date, the major research effort has concentrated on those mediators responsible for the initiation and maintenance of the pathological process. In contrast, little attention has been focused on endogenous factors responsible for the resolution of the inflammation. Heme oxygenase ((HO); EC 1.14.99.3) is the rate-limiting enzyme in the catabolism of heme to biliverdin (which is converted to bilirubin by biliverdin reductase), free iron and carbon monoxide (CO). Two isoforms of HO have been characterized, the constitutive isoform, HO-2, which is the major isoform present under physiological conditions, and the stress-induced isoform, HO-1, which has also been classified as heat-shock protein 32K (ref. 1). Increases in HO activity have been implicated in tissue protection against oxidative stress. In this communication, we describe the effects of modulating HO during an acute complement-dependent inflammatory response. Elevation of this enzyme resulted in a striking suppression, whereas inhibition of the enzyme led to a potentiation of the inflammatory response. Such novel enzyme modulation has application on the one hand to the treatment of inflammatory diseases and on the other hand to immnosuppressed states in which the impaired ability to mount an adequate inflammatory response may result in death from opportunistic infections.