Immunology. Drawing a double-edged sword

Effect of Epstein-Barr Virus DNA on the Incidence and Severity of Arthritis in a Rheumatoid Arthritis Mouse Model

Objective

We recently demonstrated that EBV DNA is correlated with proinflammatory responses in mice and in rheumatoid arthritis (RA) patients; hence, we utilized an RA mouse model to examine whether EBV DNA enhances the risk and severity of arthritis and to assess its immunomodulatory effects.

Methods

C57BL/6J mice were treated with collagen (arthritis-inducing agent), EBV DNA 6 days before collagen, EBV DNA 15 days after collagen, Staphylococcus epidermidis DNA 6 days before collagen, EBV DNA alone, or water. Mice were then monitored for clinical signs and affected joints/footpads were histologically analysed. The relative concentration of IgG anti- chicken collagen antibodies and serum cytokine levels of IL-17A and IFNϒ were determined by ELISA. The number of cells co-expressing IL-17A and IFNϒ in joint histological sections was determined by immunofluorescence.

Results

The incidence of arthritis was significantly higher in mice that received EBV DNA prior to collagen compared to mice that only received collagen. Similarly, increased clinical scores, histological scores and paw thicknesses with a decreased gripping strength were observed in groups treated with EBV DNA and collagen. The relative concentration of IgG anti-chicken collagen antibodies was significantly increased in the group that received EBV DNA 6 days prior to collagen in comparison to the collagen receiving group. On the other hand, the highest number of cells co-expressing IFNϒ and IL-17A was observed in joints from mice that received both collagen and EBV DNA.

Conclusion

EBV DNA increases the incidence and severity of arthritis in a RA mouse model. Targeting mediators triggered by viral DNA may hence be a potential therapeutic avenue.

Neutrophils promote clearance of nuclear debris following acid-induced lung injury

Neutrophils are critical mediators of host defense in pathogen-induced and sterile inflammation. Excessive neutrophil activation has been associated with increased host pathology through collateral organ damage. The beneficial aspects of neutrophil activation, particularly in sterile inflammation, are less well defined. We observed accumulation of nuclear debris in the lungs of neutropenic mice exposed to acid-induced injury compared with wild type. Size analysis of DNA debris showed that neutropenic mice were unable to degrade extracellular DNA fragments. In addition, we found that neutrophils are able to differentially express DNA-degrading and repair-associated genes and proteins. Once neutrophils are at sites of lung inflammation, they are able to phagocytose and degrade extracellular DNA. This neutrophil-dependent DNA degradation occurs in a MyD88-dependent pathway. The increased DNA debris in neutropenic mice was associated with dysregulated alveolar repair and the phenotype is rescued by intratracheal administration of DNase I. Thus, we show a novel mechanism as part of the inflammatory response, in which neutrophils engulf and degrade extracellular DNA fragments and allow for optimal organ repair.

C1Q/TNF-related protein 4 expression correlates with herpes simplex encephalitis progression

BACKGROUND

Herpes simplex encephalitis (HSE), an acute inflammatory disease of the central nervous system is caused by the herpes simplex virus infection. HSE occurs at any age, and it is often accompanied by high mortality and neurological dysfunction. The C1Q/TNF-related protein (CTRP) family, usually contains a homotrimeric structure, which comprises the N-terminal signal peptide and the C-terminal C1q globular domain. It has been demonstrated that CTRPs play pivotal roles in the inflammation process. CTRP4 is a member of the CTRP family and contains two C1q globular domains. Moreover, evidence shows that the recombinant human CTRP4 (rhCTRP4) protein exerts satisfactory anti-inflammatory effects in experimental colitis models via the NF-κB pathway. However, its role in inflammation-related neurological diseases remains unknown.

METHODS

The purpose of this study is to evaluate the expression of CTRP4 and its correlation with HSE progression. We determined the serum CTRP4 levels in a normal brain, tuberculous meningitis (TBM), bacterial meningitis (BM) and HSE.

RESULTS

We found that compared to a normal brain, TBM and BM, CTRP4 was significantly increased in HSE. Moreover, in the course of HSE, serum interleukin (IL-6) and necrosis factor-α (TNF-α) were also increased and were closely associated with CTRP4 expression. CTRP4 expression was examined by immunohistochemistry (IHC) in the normal control brain tissues, HSE, TBM and BM brain tissues. High positively expression of CTRP4 was found in HSE. In the normal brain tissue, TBM, and BM brain tissues, CTRP4 showed a weak expression. In the clinical evaluation, CTRP4 expression correlated closely with an ascending stage of the disease [mini-mental state examination (MMSE) evaluation, MRI imaging).

CONCLUSIONS

Our findings suggest that CTRP4 is highly expressed in HSE and is closely related to the progression of HSE. Thus, CTRP4 may serve as a potential severity index for HSE and targeting CTRP4 might be a promising therapeutic strategy against HSE.

Experimental models of arthritis in which pathogenesis is dependent on TNF expression

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease characterized by joint damage as well as systemic manifestations. The exact cause of RA is not known. Both genetic and environmental factors are believed to contribute to the development of this disease. Increased expression of tumor necrosis factor (TNF) has been implicated in the pathogenesis of RA. Currently, the use of anti-TNF drugs is one of the most effective strategies for the treatment of RA, although therapeutic response is not observed in all patients. Furthermore, due to non-redundant protective functions of TNF, systemic anti-TNF therapy is often associated with unwanted side effects such as increased frequency of infectious diseases. Development of experimental models of arthritis in mice is necessary for studies on the mechanisms of pathogenesis of this disease and can be useful for comparative evaluation of various anti-TNF drugs. Here we provide an overview of the field and present our own data with two experimental models of autoimmune arthritis - collagen-induced arthritis and antibody-induced arthritis in C57Bl/6 and BALB/c mice, as well as in tnf-humanized mice generated on C57Bl/6 background. We show that TNF-deficient mice are resistant to the development of collagen-induced arthritis, and the use of anti-TNF therapy significantly reduces the disease symptoms. We also generated and evaluated a fluorescent detector of TNF overexpression in vivo. Overall, we have developed an experimental platform for studying the mechanisms of action of existing and newly developed anti-TNF drugs for the treatment of rheumatoid arthritis.

Dissecting the Role of Anti-ganglioside Antibodies in Guillain-Barré Syndrome: an Animal Model Approach

Guillain-Barré syndrome (GBS) is an autoimmune polyneuropathy disease affecting the peripheral nervous system (PNS). Most of the GBS patients experienced neurological symptoms such as paresthesia, weakness, pain, and areflexia. There are also combinations of non-neurological symptoms which include upper respiratory tract infection and diarrhea. One of the major causes of GBS is due largely to the autoantibodies against gangliosides located on the peripheral nerves. Gangliosides are sialic acid-bearing glycosphingolipids consisting of a ceramide lipid anchor with one or more sialic acids attached to a neutral sugar backbone. Molecular mimicry between the outer components of oligosaccharide of gangliosides on nerve membrane and lipo-oligosaccharide of microbes is thought to trigger the autoimmunity. Intra-peritoneal implantation of monoclonal ganglioside antibodies secreting hybridoma into animals induced peripheral neuropathy. Recent studies demonstrated that injection of synthesized anti-ganglioside antibodies raised by hybridoma cells into mice initiates immune response against peripheral nerves, and eventually failure in peripheral nerve regeneration. Accumulating evidences indicate that the conjugation of anti-ganglioside monoclonal antibodies to activating FcγRIII present on the circulating macrophages inhibits axonal regeneration. The activation of RhoA signaling pathways is also involved in neurite outgrowth inhibition. However, the link between these two molecular events remains unresolved and requires further investigation. Development of anti-ganglioside antagonists can serve as targeted therapy for the treatment of GBS and will open a new approach of drug development with maximum efficacy and specificity.

The immunoglobulin, IgG Fc receptor and complement triangle in autoimmune diseases

Immunoglobulin G (IgG)-mediated activation of complement and IgG Fc receptors (FcγRs) are important defense mechanisms of the innate immune system to ward off infections. However, the same mechanisms can drive severe and harmful inflammation, when IgG antibodies react with self-antigens in solution or tissues, as described for several autoimmune diseases including systemic lupus erythematosus, rheumatoid arthritis, and immune vasculitis. More specifically, IgG immune complexes (ICs) can activate all three pathways of the complement system resulting in the generation of C3 and C5 cleavage products that can activate a panel of different complement receptors on innate and adaptive immune cells. Importantly, complement and FcγRs are often co-expressed on inflammatory immune cells such as neutrophils, monocytes, macrophages or dendritic cells and act in concert to mediate the inflammatory response in autoimmune diseases. In this context, the cross-talk between the receptor for the anaphylatoxin C5a, i.e. C5ar1 (CD88) and FcγRs is of major importance. Recent data suggest a model of bidirectional regulation, in which CD88 acts upstream of FcγRs and sets the threshold for FcγR-dependent effector responses by regulating the ratio between activating and inhibitory FcγRs. Vice versa, FcγR ligation can either amplify or block C5aR-mediated effector functions, depending on whether IgG IC aggregate activating or inhibitory FcγRs. Further, complement and FcγRs cooperate on B cells and on follicular dendritic cells to regulate the development of autoreactive B cells, their differentiation into plasma cells and, eventually, the production of autoantibodies. Here, we will give an update on recent findings regarding this complex regulatory network between complement and FcγRs, which may also regulate the inflammatory response in allergy, cancer and infection.

Analysis of effects induced by a pollock protein hydrolysate on early development, innate immunity and the bacterial community structure of first feeding of Atlantic halibut (Hippoglossus hippoglossus L.) larvae

A pollock protein hydrolysate was used for enrichment of the live feed offered to halibut larvae from the onset of exogenous feeding and the effects of treatment on selected innate immune parameters studied. The effects of treatment on the bacterial community structure of larvae were furthermore studied using the PCR-DGGE method. C3 and lysozyme were identified in larvae already at the onset of first feeding and low concentrations of IgM detected at this stage indicate maternal origin. Endogenous production of IgM was validated in the gastrointestinal tract of larvae from 29 days post onset of first feeding, with similar concentrations found in both groups. Feeding the peptide-enriched live feed stimulated production of lysozyme and affected the distribution of C3 in larval tissue but survival and normal development of halibut larvae were not affected by the treatment. Vibrio sp. and Pseudoalteromonas sp. dominated the bacterial community of larvae from both groups and peptide enrichment of the live feed was not found to affect the bacterial community structure associated with surface sterilized larvae.

Antibody-induced arthritis: disease mechanisms and genes involved at the effector phase of arthritis

During the development of rheumatoid arthritis (RA) autoantibodies to IgG-Fc, citrullinated proteins, collagen type II (CII), glucose 6 phosphoisomerase (G6PI) and some other self-antigens appear. Of these, a pathogenic effect of the anti-CII and anti-G6PI antibodies is well demonstrated using animal models. These new antibody mediated arthritis models have proven to be very useful for studies involved in understanding the molecular pathways of the induction of arthritis in joints. Both the complement and FcgammaR systems have been found to play essential roles. Neutrophils and macrophages are important inflammatory cells and the secretion of tumour necrosis factor-alpha and IL-1beta is pathogenic. The identification of the genetic polymorphisms predisposing to arthritis is important for understanding the complexity of arthritis. Disease mechanisms and gene regions studied using the two antibody-induced arthritis mouse models (collagen antibody-induced arthritis and serum transfer-induced arthritis) are compared and discussed for their relevance in RA pathogenesis.

Complement component C3 transcription in Atlantic halibut (Hippoglossus hippoglossus L.) larvae

The complement systems of fish are well developed and play an important role in the innate immune response. Complement C3 is the central protein of all three activation pathways and is the major opsonin of the complement system and essential for the generation of the membrane attack complex. A 1548 bp part of complement component C3 was isolated from a halibut liver cDNA library by immunoscreening. The deduced amino acid sequence showed that this part of halibut C3 contained key amino acids for factor H, I and properdin binding as well as two N-glycosylation sites. Digoxigenine labelled mRNA probes were synthesised and the transcription of C3 was monitored in three larval stages at 206, 430 and 1000 degrees d (30, 50 and 99 days post hatching), by in situ hybridisation. C3 mRNA was detected in muscle, liver, brain, chondrocytes, spinal cord, eye, intestines, oesophagus and kidney. These findings are in accordance with a former immunohistochemical study on halibut C3 protein ontogeny, indicating that C3 is indeed locally expressed in many organs from the youngest stages on. Complement may thus be linked to the formation and generation of different organs during development and play an important role in the early immune response of halibut larvae.

The ontogenic transcription of complement component C3 and Apolipoprotein A-I tRNA in Atlantic cod (Gadus morhua L.)--a role in development and homeostasis?

The complement system is important both in the innate and adaptive immune response, with C3 as the central protein of all three activation pathways. Apolipoprotein A-I (ApoLP A-I), a high-density lipoprotein (HDL), has been shown to have a regulatory role in the complement system by inhibiting the formation of the membrane attack complex (MAC). Complement has been associated with apoptotic functions, which are important in the immune response and are involved in organ formation and homeostasis. mRNA probes for cod C3 and ApoLP A-I were synthesized and in situ hybridisation used to monitor the ontogenic development of cod from fertilised eggs until 57 days after hatching. Both C3 and ApoLP A-I transcription was detected in the central nervous system (CNS), eye, kidney, liver, muscle, intestines, skin and chondrocytes at different stages of development. Using TUNEL staining, apoptotic cells were identified within the same areas from 4 to 57 days posthatching. The present findings may suggest a role for C3 and ApoLP A-I during larval development and a possible role in the homeostasis of various organs in cod.

The ontogeny of complement component C3 in Atlantic cod (Gadus morhua L.)--an immunohistochemical study

The complement system in fish is well developed and plays an important role in the immune response. Very little is known about the ontogeny of C3 in fish and no study has previously been done on the development of C3 in teleosts. In this study we have detected the presence of C3 in cod larvae from the age of 1 day post hatching (p.h.) till 57 days p.h., using immunohistochemistry. The specific primary antibodies used, were produced against the beta-chain of cod C3. Immunostaining on cod larvae sections revealed that C3 is detectable in the yolksac membrane from day 1 p.h., and in liver, brain, kidney and muscle from day 2 p.h. C3 was also detected in other organs such as eye, notochord, stomach, intestines, pancreas, heart and gills at different stages of cod larval development. These findings suggest that complement is not only important in immune defence against invading pathogens but may also play a role in the formation and generation of different organs.

Dancing with complement C4 and the RP-C4-CYP21-TNX (RCCX) modules of the major histocompatibility complex

The number of the complement component C4 genes varies from 2 to 8 in a diploid genome among different human individuals. Three quarters of the C4 genes in Caucasian populations have the endogenous retrovirus, HERV-K(C4), in the ninth intron. The remainder does not. The C4 serum proteins are highly polymorphic and their concentrations vary from 100 to approximately 1000 microg/ml. There are two distinct classes of C4 protein, C4A and C4B, which have diversified to fulfill (a) the opsonization/immunoclearance purposes and (b) the well-known complement function in the killing of microbes by lysis and neutralization, respectively. Many infectious and autoimmune diseases are associated with complete or partial deficiency of C4A and/or C4B. The adverse effects of high C4 gene dosages, however, are just emerging, as the concepts of human C4 genetics are revised and accurate techniques are applied to distinguish partial deficiencies from differential expression caused by unequal C4A and C4B gene dosages and gene sizes. This review attempts to dissect the sophisticated genetics of complement C4A and C4B. The emphases are on the qualitative and quantitative diversities of C4 genotypes and phenotypes. The many allotypic variants and the processed products of human and mouse C4 proteins are described. The modular variation of C4 genes together with the serine/threonine nuclear kinase gene RP, the steroid 21-hydroxylase CYP21, and extracellular matrix protein TNX (RCCX modules) are investigated for the effects on homogenization of C4 protein polymorphisms, and on the unequal genetic crossovers that knocked out the functions of CYP21 and/or TNX. Furthermore, the influence of the endogenous retrovirus HERV-K(C4) on C4 gene expression and the dispersal of HERV-K(C4) family members in the human genome are discussed.

Collagen type II-specific monoclonal antibody-induced arthritis in mice: description of the disease and the influence of age, sex, and genes

Transfer of collagen type II (CII)-specific monoclonal antibodies induces an acute form of arthritis (collagen type II antibody-induced arthritis, CAIA) in naïve mice. Arthritis was induced using a pair of monoclonal antibodies M2139 and CIIC1, binding to J1 and C1(I) epitopes of CII, respectively. Thereafter, lipopolysaccharide injection was used to increase the incidence and severity of the disease. This model was used to investigate the effect of genes, age, and sex as well as effector cells in the end-stage effector phase of arthritis pathogenesis. Injection of a single monoclonal antibody induced arthritis only after lipopolysaccharide stimulation. CAIA showed differences in disease penetration among the susceptible strains indicating the importance of non-major histocompatibility complex genes on the antibody effector pathway. B-cell-deficient mice were susceptible to CAIA and in some genetic backgrounds B-cell deficiency leads to enhanced arthritis. Histology of the affected paws revealed massive infiltrations of neutrophils along with bone and cartilage erosion, pannus formation, and fibrin deposition. Depletion of neutrophils significantly reduced the incidence and severity of the disease. CAIA susceptibility increased with age. Males were more susceptible than females and estrogen treatment decreased the development of arthritis. We conclude that CAIA is an acute arthritis triggered by antibody binding and neutrophils bypassing immune activation but with many characteristics in common with collagen-induced arthritis.

Identification of cDNA encoding a serine protease homologous to human complement C1r precursor from grafted mouse skin

We isolated a cDNA clone from grafted mouse skin that encodes a serine protease homologous to human C1r. The C1r protease is involved in the activation of the first component of the classical pathway in the complement system. In order to identify novel transcripts whose expression is regulated in grafted mouse skin, we first performed differential display reverse transcription polymerase chain reaction analysis and obtained 18 partial cDNA clones whose protein products are likely to play an important role in allograft rejection. One of these showed significant sequence homology with human complement C1r precursor. The other clones displayed no homology to any known sequences, however. Northern blot analysis demonstrated that the level of this transcript was upregulated in day 8 postgrafted skin. The full-length cDNA 2121 nucleotides in length obtained from screening a mouse skin cDNA library contained a single open reading frame encoding 707 amino acid residues with a calculated molecular weight of 80,732 Da. Its deduced amino acid sequence revealed an 81% identity and 89% similarity to the human C1r counterpart. In particular, mouse C1r contained His501, Asp559, and Ser656, which were conserved among this group of serine proteases. This protein was thus designated as mouse C1r. We have expressed a truncated fragment of C1r protein without the N-terminal hydrophobic sequence in Escherichia coli and generated a polyclonal antibody against it. Subsequent immunohistochemical analysis confirmed that mouse C1r was significantly expressed 8 d after the skin graft in both allografted and autografted skins, compared with normal skins. These collective data suggest that a component of the complement system, C1r, might contribute to the graft versus host immune responses in mice.

Genetic, structural and functional diversities of human complement components C4A and C4B and their mouse homologues, Slp and C4

The complement protein C4 is a non-enzymatic component of the C3 and C5 convertases and thus essential for the propagation of the classical complement pathway. The covalent binding of C4 to immunoglobulins and immune complexes (IC) also enhances the solubilization of immune aggregates, and the clearance of IC through complement receptor one (CR1) on erythrocytes. Human C4 is the most polymorphic protein of the complement system. In this review, we summarize the current concepts on the 1-2-3 loci model of C4A and C4B genes in the population, factors affecting the expression levels of C4 transcripts and proteins, and the structural, functional and serological diversities of the C4A and C4B proteins. The diversities and polymorphisms of the mouse homologues Slp and C4 proteins are described and contrasted with their human homologues. The human C4 genes are located in the MHC class III region on chromosome 6. Each human C4 gene consists of 41 exons coding for a 5.4-kb transcript. The long gene is 20.6 kb and the short gene is 14.2 kb. In the Caucasian population 55% of the MHC haplotypes have the 2-locus, C4A-C4B configurations and 45% have an unequal number of C4A and C4B genes. Moreover, three-quarters of C4 genes harbor the 6.4 kb endogenous retrovirus HERV-K(C4) in the intron 9 of the long genes. Duplication of a C4 gene always concurs with its adjacent genes RP, CYP21 and TNX, which together form a genetic unit termed an RCCX module. Monomodular, bimodular and trimodular RCCX structures with 1, 2 and 3 complement C4 genes have frequencies of 17%, 69% and 14%, respectively. Partial deficiencies of C4A and C4B, primarily due to the presence of monomodular haplotypes and homo-expression of C4A proteins from bimodular structures, have a combined frequency of 31.6%. Multiple structural isoforms of each C4A and C4B allotype exist in the circulation because of the imperfect and incomplete proteolytic processing of the precursor protein to form the beta-alpha-gamma structures. Immunofixation experiments of C4A and C4B demonstrate > 41 allotypes in the two classes of proteins. A compilation of polymorphic sites from limited C4 sequences revealed the presence of 24 polymophic residues, mostly clustered C-terminal to the thioester bond within the C4d region of the alpha-chain. The covalent binding affinities of the thioester carbonyl group of C4A and C4B appear to be modulated by four isotypic residues at positions 1101, 1102, 1105 and 1106. Site directed mutagenesis experiments revealed that D1106 is responsible for the effective binding of C4A to form amide bonds with immune aggregates or protein antigens, and H1106 of C4B catalyzes the transacylation of the thioester carbonyl group to form ester bonds with carbohydrate antigens. The expression of C4 is inducible or enhanced by gamma-interferon. The liver is the main organ that synthesizes and secretes C4A and C4B to the circulation but there are many extra-hepatic sites producing moderate quantities of C4 for local defense. The plasma protein levels of C4A and C4B are mainly determined by the corresponding gene dosage. However, C4B proteins encoded by monomodular short genes may have relatively higher concentrations than those from long C4A genes. The 5' regulatory sequence of a C4 gene contains a Spl site, three E-boxes but no TATA box. The sequences beyond--1524 nt may be completely different as the C4 genes at RCCX module I have RPI-specific sequences, while those at Modules II, III and IV have TNXA-specific sequences. The remarkable genetic diversity of human C4A and C4B probably promotes the exchange of genetic information to create and maintain the quantitative and qualitative variations of C4A and C4B proteins in the population, as driven by the selection pressure against a great variety of microbes. An undesirable accompanying byproduct of this phenomenon is the inherent deleterious recombinations among the RCCX constituents leading to autoimmune and genetic disorders.

An immediate, allergic skin reaction to aprotinin after reexposure to fibrin sealant

BACKGROUND

The safety of fibrin tissue adhesives has been a concern since they entered wide clinical application. Most commercially available kits contain the proteolytic inhibitor, aprotinin, to stabilize the fibrin clot. A bovine protein, this substance has an allergenic potency.

CASE REPORT

This case report presents a patient who had a generalized allergic skin reaction, probably triggered by aprotinin upon reexposure to fibrin sealant injected subgaleally to achieve closure of a liquor fistula after neurosurgical treatment. The serologic investigation revealed aprotinin-specific IgE and IgG. From 1990 through 1998, reports of five allergic reactions following 1 million exposures to fibrin sealant were made to the manufacturer. The clinical relevance of allergic reactions to aprotinin contained in fibrin sealants and measures to avoid them are discussed.

CONCLUSION

These hypersensitivity reactions are extremely rare (incidence, 0.5/100,000 for all reactions and 0.3/100,000 for serious reactions), but they must be kept in mind as possible adverse events after repeated applications of fibrin sealants within a few weeks.

The significance of preformed aprotinin-specific antibodies in cardiosurgical patients

Acute hypersensitivity reactions are serious complications of reexposure to aprotinin. Previous contact via infusions or fibrin tissue adhesives can induce specific antibodies. In this study, we aimed to elucidate the preoperative prevalence of aprotinin-specific antibodies in patients scheduled for cardiac operations. Sera of 520 consecutive cardiosurgical patients were collected preoperatively and screened retrospectively for aprotinin-specific IgG using a standard enzyme-linked immunosorbent assay (ELISA). Positive sera were analyzed also for aprotinin-specific IgA (ELISA) and IgE (fluorescence enzyme immunoassay). The histories of all patients were reviewed with focus on aprotinin preexposure. Of 520 patients, 22 (4%) had specific IgG. Only three of these had a documented aprotinin preexposure. Of 448 patients exposed to aprotinin intraoperatively, 15 had preformed specific antibodies. The only patient presenting with severe anaphylaxis was positive for both IgG and IgE, and had a recent IV preexposure in cardiovascular surgery. The presence of aprotinin-specific IgG alone seems not to induce adverse reactions on exposure. Exposure history alone is not sensitive enough to identify patients with aprotinin-specific antibodies.

IMPLICATIONS

Anaphylaxis on IV reexposure to aprotinin is a medical emergency. The clinical significance of preformed aprotinin-specific IgG remains questionable, whereas preformed IgE was present in the only patient who suffered from severe anaphylaxis on reexposure to aprotinin. Preformed antibodies are not reliably predicted by exposure history.

Aprotinin in fibrin tissue adhesives induces specific antibody response and increases antibody response of high-dose intravenous application

BACKGROUND

In cardiac operations, aprotinin therapy is used either locally as a component of commercially available fibrin tissue adhesives, intravenously, or combined. Our aim was to examine the formation of aprotinin-specific antibodies with regard to the application mode.

METHODS

Sera of 150 patients who had undergone cardiac operations and were receiving aprotinin therapy for the first time were sampled before the operation and at medians of 3.5 and 13.3 months after the operation. Aprotinin-specific IgG including all subgroups and aprotinin-specific IgE were analyzed. Aprotinin was given locally (as contained in fibrin sealant; n = 45; median dose, 6000 KIU), intravenously (n = 46; 2.000 x 10(6) KIU), and combined (n = 59; 2.012 x 10(6) KIU).

RESULTS

At 3.5 months, the prevalence of aprotinin-specific IgG antibodies was 33% (15/45 patients) after local, 28% (13/46 patients) after intravenous, and 69% (41/59 patients) after combined exposure (P =.0001). At 13.3 months, the prevalence of aprotinin-specific IgG antibodies was 10% (4/41 patients) after local, 31% (13/42 patients) after intravenous, and 49% (28/57 patients) after combined exposure. Total aprotinin dose was similar in patients who were antibody positive and negative. Before the operation, no aprotinin-specific antibodies were detected. Aprotinin-specific IgE were not found after the operation.

CONCLUSION

Local aprotinin contact induces a specific immune response and reinforces that of intravenous exposure. The antibody spectrum is identical to the immune response induced by intravenous exposure. Any exposure should be documented. For use in cardiac operations as a hemostyptic, the necessity itself and alternatives for aprotinin as a stabilizing agent merit consideration.

Transgenic mice overexpressing the complement inhibitor crry as a soluble protein are protected from antibody-induced glomerular injury

Complement receptor 1-related gene/protein y (Crry) is a potent murine membrane complement regulator that inhibits classical and alternative pathway C3 convertases. In nephrotoxic serum (NTS) nephritis, injected antibodies (Abs) bind to glomeruli, leading to complement activation and subsequent glomerular injury and albuminuria. To study the phenotypic effects of continuous complement pathway blockade, transgenic mice were created that express recombinant soluble (rs) Crry directed by the broadly active and heavy metal-inducible metallothionein-I promoter. One transgenic line expressing high levels of rsCrry was propagated. Serum rsCrry levels were 18.7 +/- 2.7 microg/ml (n = 5) at basal level and increased to 118.1 +/- 20.6 microg/ml 4 d after addition of zinc to the drinking water. By reverse transcription polymerase chain reaction (RT-PCR), transgene messenger (m)RNA was present in liver, kidney, brain, lung, and spleen, but not in heart. By in situ RT-PCR analysis of kidneys, transgene mRNA was widely expressed both in renal glomeruli and tubules. Urinary excretion of rsCrry was 113.4 +/- 22.4 microg/ml with a fractional excretion relative to creatinine of 13.2 +/- 2.7%, consistent with local renal production of rsCrry and secretion into urine. The founder and all transgene positive adult animals have remained healthy with no mortality or apparent phenotypic abnormalities, including infection or immune complex disease. To determine whether rsCrry blocked complement-mediated injury, NTS nephritis was induced by injection of NTS immunoglobulin (Ig)G, followed by an 18-h urine collection to quantitate the excretion of albumin as a measure of glomerular injury. In transgene-negative littermates (n = 15), transgene-positive animals (n = 10), and transgene-positive animals fed zinc (n = 10), albuminuria was 4,393 +/- 948, 1,783 +/- 454, and 1,057 +/- 277 microg/mg creatinine, respectively (P < 0.01 by ANOVA). Glomerular C3 was evident by immunofluorescence staining in 12/15 transgene-negative animals, but in none of the transgene-positive animals fed zinc. Thus, we have produced the first transgenic animals that overexpress a soluble C3 convertase inhibitor. rsCrry expression markedly ameliorates an Ab-induced disease model in vivo. These results support the hypothesis that continuous complement inhibition at the C3 convertase step is feasible and effective in complement-mediated injury states.

Direct analysis of single rat peritoneal mast cells with laser vaporization/ionization mass spectrometry

A linear time-of-flight mass spectrometer was used as a detector for flow cytometry. These two techniques were coupled by a laser vaporization/ionization interface. The estimated mass detection limit of the combined system was 20 amol of serotonin standard with one laser pulse. An aqueous buffer at physiological pH was used to ensure compatibility with cells. Rat peritoneal mast cells (RPMCs) were dispensed into the mass spectrometer in a single file confined within a 20-micron-i.d. capillary. By using the mass spectrometer as a detector, no precolumn staining or derivatization is required. Determination of serotonin and histamine in individual cells was demonstrated. With this method, hundreds of cells can be analyzed within a few minutes. The average amounts of histamine and serotonin per RPMC were found to be 0.75 +/- 0.33 and 0.11 +/- 0.06 fmol, respectively. No correlation was found between the amounts of the two amines in each cell.

Fibrin sealant, aprotinin, and immune response in children undergoing operations for congenital heart disease

OBJECTIVE

Most commercially available fibrin sealants contain aprotinin in doses of 1500 kallikrein inactivator units per milliliter. They are used in many operative disciplines. An elevated risk of hypersensitivity reactions exists at reexposure to aprotinin. Our aim was to examine the immunogenic potency of aprotinin as a fibrin sealant content.

METHODS

We investigated 49 children with operatively treated congenital heart disease. All patients received aprotinin only topically as contained in fibrin sealant. Serum samples were drawn preoperatively, 1 week, 2 weeks, 6 weeks, and approximately 1 year after operation. They were analyzed for aprotinin-specific immunoglobulin G antibodies with a standard enzyme-linked immunosorbent assay and a fluorescence enzyme immunoassay for aprotinin-specific immunoglobulin E antibodies.

RESULTS

At 1 week, 2 weeks, 6 weeks, and 1 year, we found prevalences of 8% (2 of 26), 8% (2 of 24), 6% (3 of 49), and 0% for aprotinin-specific Immunoglobulin E, and for aprotinin-specific immunoglobulin G 8% (2 of 26), 17% (4 of 24), 39% (19 of 49), and 12% (5 of 41). The doses of aprotinin given did not differ significantly in antibody-negative and antibody-positive patients; no significant factors could predict the immune response.

CONCLUSIONS

Our findings show the existence of a subgroup of patients who had aprotinin-specific antibodies develop after topical aprotinin application. Any use of aprotinin must be carefully documented. If aprotinin use is planned in patients who previously underwent a surgical procedure, preexposure to aprotinin in any form must be sought to avoid unexpected anaphylactic reactions. The necessity itself and alternatives for aprotinin as a stabilizing agent in fibrin sealants merit consideration.

Required early complement activation in contact sensitivity with generation of local C5-dependent chemotactic activity, and late T cell interferon gamma: a possible initiating role of B cells

Complement (C) is an important component of innate immunity, and was also shown recently to participate in induction of acquired B cell humoral immunity. In this study, we present evidence that C also participates in acquired T cell immunity. We found that C was involved in early events of the efferent elicitation phase of contact sensitivity (CS), and delayed-type hypersensitivity (DTH). Thus, CS and DTH were inhibited by administration of a C-blocker, soluble recombinant C receptor-1 (sCR1), when given 30 min before, but not 3 h after local antigen challenge. Among C components, local C5 were thought crucial to elicitation of CS, since local administration of anti-C5 monoclonal antibodies or locally injected C-depleting cobra venom factor also inhibited CS and DTH. These findings were consistent with our previous finding of the importance of C5 for CS elicitation, using congenitally C5-deficient mice. To dissect the mechanism of C dependence in CS, we demonstrated that locally increased early macrophage chemotactic activity (probably C5a) in evolving CS skin extracts, as well as late elaboration of IFN-gamma, were both inhibited by anti-C treatment. In addition, histological analysis showed that leukocyte recruitment into CS ear sites was similarly C-dependent. Furthermore, an initiating role of B cell-derived C-fixing immunoglobulin was suggested by demonstration of impaired CS responses in B cell-deficient mice. In summary, these results suggest that C was activated locally, perhaps via a B cell product, in an important early component of the stepwise events necessary to elicit CS, leading to local production of C5-dependent macrophage chemotactic activity and later IFN-gamma, and subsequently leading to cell infiltration, for development of T cell-dependent CS.

Impaired inflammatory responses in the reverse arthus reaction through genetic deletion of the C5a receptor

We recently demonstrated that gene-targeted disruption of the C5a anaphylatoxin receptor prevented lung injury in immune complex-mediated inflammation. In this study, we compare the effect of C5aR deficiency in immune complex-induced inflammation in the peritoneal cavity and skin with the results derived from our immune complex alveolitis model. C5aR- deficient mice exhibit decreased migration of neutrophils and decreased levels of TNF-alpha and interleukin 6 in the peritoneal reverse passive Arthus reaction compared to their wild-type littermates. In the reverse passive Arthus reaction in the skin the C5aR was also required for the full expression of neutrophil influx and edema formation; C5aR-deficient mice showed reduced neutrophil migration and microvascular permeability changes. In contrast to our studies in immune complex-induced lung inflammation, C5aR deficiency does not completely prevent injury in the peritoneal cavity and skin. These data indicate a dominant role for the C5aR and its ligand in the reverse passive Arthus reaction in the lung and a synergistic role together with other inflammatory mediators in immune complex-mediated peritonitis and skin injury.

Cellular mechanisms of bone repair

The extent of callus formation about a bone fracture depends on the rigidity of fracture fixation. The mechanism that converts the mechanical stimulus into the biologic response is unknown. On the basis of existing literature, an attempt has been made to define a model that explains this mechanobiologic transduction. Once integrity of the bone has been disrupted, a sequence of biochemical and cellular events commences that induces inflammatory reactions. Messengers (e.g., metabolites of the clotting or complement system, eicosanoids, or growth factors) are released or activated. They control the migration, proliferation, and protein synthesis of cells that are essential for angiogenesis and connective tissue formation. The key component in this inflammatory sequence seems to be the macrophage. Growth factors (e.g., released by macrophages) stimulate endothelial cells to form capillaries and mesenchymal cells to synthesize their matrix. In mechanically neutral areas, the fracture cavity is revascularized and osteoblasts proliferate and form bone. In mechanically instable fracture areas, spreading capillaries are disrupted by shear forces. In these areas, therefore, the milieu becomes hypoxic again. This milieu seems to support the differentiation of chondrocytes that stabilize the fracture by cartilage formation. If the strength of repair tissue is surpassed, the disrupture of the repair tissue triggers the mechanisms of inflammation again and additional cells immigrate and proliferate. Their protein synthesis increases repair callus. The increase of callus formation, however, stops when the tissue is capable of resisting motion. Links to the callus formation in osteitis are shown.

Downstream signals initiated in mast cells by Fc epsilon RI and other receptors

The significant contributions this past year to our understanding of IgE receptor (Fc epsilon RI) signaling in mast cells include studies with truncated Syk in a vaccinia expression system and Syk-negative variants of rat basophilic (RBL-2H3) cells. These studies demonstrate an essential role for Syk in initiating signals for secretion and release of arachidonic acid via phospholipase A2 and mitogen-activated protein kinase. A newly recognized addition to the repertoire of Fc epsilon RI-mediated signaling systems is the activation of sphingosine kinase, which contributes to calcium mobilization in mast cells. Advances have been made in our understanding of other receptors that regulate proliferation and differentiation of mast cells, and in our understanding of the ability of mast cells to mount acquired and acute responses to antigenic and bacterial challenge.

Amelioration of lupus-like autoimmune disease in NZB/WF1 mice after treatment with a blocking monoclonal antibody specific for complement component C5

New Zealand black x New Zealand white (NZB/W) F1 mice spontaneously develop an autoimmune syndrome with notable similarities to human systemic lupus erythematosus. Female NZB/WF1 mice produce high titers of antinuclear antibodies and invariably succumb to severe glomerulonephritis by 12 months of age. Although the development of the immune-complex nephritis is accompanied by abundant local and systemic complement activation, the role of proinflammatory complement components in disease progression has not been established. In this study we have examined the contribution of activated terminal complement proteins to the pathogenesis of the lupus-like autoimmune disease. Female NZB/W F1 mice were treated with a monoclonal antibody (mAb) specific for the C5 component of complement that blocks the cleavage of C5 and thus prevents the generation of the potent proinflammatory factors C5a and C5b-9. Continuous therapy with anti-C5 mAb for 6 months resulted in significant amelioration of the course of glomerulonephritis and in markedly increased survival. These findings demonstrate an important role for the terminal complement cascade in the progression of renal disease in NZB/W F1 mice, and suggest that mAb-mediated C5 inhibition may be a useful approach to the therapy of immune-complex glomerulonephritis in humans.

Impaired IgG-dependent anaphylaxis and Arthus reaction in Fc gamma RIII (CD16) deficient mice

The family of receptors for IgG (Fc gamma R) plays an essential role in antibody-mediated effector functions of the immune system. However, the specific contribution of each of the Fc gamma R classes to in vivo immune reactions is still unclear. Here, we demonstrate that mice deficient for the ligand-binding alpha chain of Fc gamma RIII lack NK cell-mediated antibody-dependent cytotoxicity and phagocytosis of IgG1-coated particles by macrophages. Strikingly, these mice lack IgG-mediated mast cell degranulation, are resistant to IgG-dependent passive cutaneous anaphylaxis, and exhibit an impaired Arthus reaction. These results indicate a prominent role for Fc gamma RIII in inflammatory and anaphylactic responses, making this receptor a potential target in immunotherapy.

Complement activation on human neuroblastoma cell lines in vitro: route of activation and expression of functional complement regulatory proteins

Two human neuroblastoma cell lines activated the classical pathway of complement in serum. Activation caused the opsonisation of these cells with complement fragments but with moderate cell killing. Neuroblastoma expressed regulators MCP and CD59 but did not express DAF or CR1. Neutralisation of CD59 rendered the cells susceptible to killing. Neuroblastoma also expressed C1-inhibitor, factor H, clusterin and S-protein. Expression of several regulators was enhanced by incubation with cytokines. Complement inhibition using soluble CRI markedly reduced opsonisation and killing of neuroblastoma. Our results suggest that complement might play a role in neuronal loss and that treatment with complement inhibitors might be of therapeutic value.

Multiple loss of effector cell functions in FcR gamma-deficient mice

Immunoglobulin Fc receptor (FcR) gamma subunit is a component of low affinity receptor for IgG, Fc gamma RIII, as well as high affinity receptor for IgE, Fc epsilon RI. This subunit is required for efficient surface expression of these FcRs on various cells in immune system. The FcR gamma-deficient mice, generated by gene targeting in embryonic stem cells, exhibit multiple defects in FcR-mediated effector cell responses, including absence of phagocytic activity against opsonized red blood cells by activated macrophages, loss of antibody-dependent cell-mediated cytotoxicity manifested by IL-2-induced splenic NK cells, and unresponsiveness of mast cells to crosslinking of IgE on these cells. These results demonstrate an indispensable role of FcR gamma for functional expression of FcRs, and clearly indicate the importance of Fc gamma RIII as well as Fc epsilon RI for these effector functions. Since FcR gamma-deficient mice is unable to mount the type II and type III hypersensitivity reactions, it is suggested that FcRs play pivotal roles in initiating these reaction cascades. The mutant mice should prove to be useful in evaluating FcRs in various humoral and cellular immune responses, and in developing new strategies for treatment of immunodeficiency as well as autoimmune disorders.