Innate recognition of bacteria in human milk is mediated by a milk-derived highly expressed pattern recognition receptor, soluble CD14

Little is known about innate immunity to bacteria after birth in the hitherto sterile fetal intestine. Breast-feeding has long been associated with a lower incidence of gastrointestinal infections and inflammatory and allergic diseases. We found in human breast milk a 48-kD polypeptide, which we confirmed by mass spectrometry and sequencing to be a soluble form of the bacterial pattern recognition receptor CD14 (sCD14). Milk sCD14 (m-sCD14) concentrations were up to 20-fold higher than serum sCD14 from nonpregnant, pregnant, or lactating women. In contrast, lipopolysaccharide (LPS)-binding protein was at very low levels. Mammary epithelial cells produced 48-kD sCD14. m-sCD14 mediated activation by LPS and whole bacteria of CD14 negative cells, including intestinal epithelial cells, resulting in release of innate immune response molecules. m-sCD14 was undetectable in the infant formulas and commercial (cows') milk tested, although it was present in bovine colostrum. These findings indicate a sentinel role for sCD14 in human milk during bacterial colonization of the gut, and suggest that m-sCD14 may be involved in modulating local innate and adaptive immune responses, thus controlling homeostasis in the neonatal intestine.

Membrane attack complex formation on yeast as trigger of selective release of terminal complement proteins from human polymorphonuclear leukocytes

It has recently been shown that measurable amounts of complement proteins, C6 and in particular C7, are released from human polymorphonuclear leukocytes (PMNs). The aim of the present study was to investigate the impact of opsonized Candida albicans on this release. Stimulation with opsonized C. albicans led to a rapid and sustained increase of C6 and C7 in the cell culture supernatant beginning within 5 min of placing in co-culture, whereas co-culture with unopsonized C. albicans or C. albicans mock-opsonized with inactivated human serum did not affect the release. In contrast, even after stimulation employing opsonized C. albicans, no release of the complement component C8 and only trace amounts of C9 were detected. The presence of the membrane attack complex (MAC) on C. albicans after opsonization was demonstrated by indirect immunofluorescence. Opsonization of C. albicans with human serum deficient in or depleted of a terminal complement component resulted in only minor stimulation of C6 and C7 release, although C3 deposition on the surface of C. albicans was not affected as determined by direct immunofluorescence. Detailed analyses with inactivated or deficient sera showed that detection of C6 and C7 was not due to insufficient washing of the opsonized yeast prior to co-culture and suggest that only a small proportion of these proteins was derived from the membrane bound and then cleaved off MAC. Thus, these findings imply that MAC on the fungal surface may represent an additional trigger for the release of C6 and C7 from PMNs, suggesting a new role for the terminal complement complex (TCC) on target membranes as modulator of PMN functions locally at the site of inflammation.

Production and functional characterization of a soluble recombinant form of mouse CD59

This report describes the engineering, expression, purification and functional characterization of a soluble recombinant form of murine CD59 (srMoCD59). We report the expression in Chinese hamster ovary (CHO) cells of a modified mouse CD59 cDNA that had been truncated at D-74, resulting in the loss of the glycosylphosphatidyl inositol (GPI) anchor, and containing six additional C-terminal histidines. The expressed srMoCD59 was purified from tissue culture supernatant by means of its poly-histidine tag using immobilized metal affinity chromatography. In comparison with CD59 on mouse erythrocytes, the srMoCD59 had a reduced molecular weight (18-20 000 as compared with 20-28 000 for GPI-anchored srMoCD59). The terminal complement inhibitory capacity of this soluble recombinant protein was assessed using two methods: a cobra venom factor (CVF)-triggered 'reactive-lysis' system and a C5b-7 site assay. In both assays, srMoCD59 inhibited lysis by the sera from all three species tested in the rank order mouse > rat >> human. The amount of srMoCD59 required to produce 50% inhibition of lysis in the C5b-7 site assay, using purified terminal components to develop lysis, was 10-fold less than that required in the same assay when EDTA serum was used as a source of C8 and C9, or in the CVF reactive lysis system. These data indicate that the presence of serum markedly interfered with the activity of srMoCD59 and have important implications for the use of recombinant soluble CD59 analogues as therapeutic agents in complement-mediated diseases.

Comparison of the suppressive effects of soluble CR1 and C5a receptor antagonist in acute arthritis induced in rats by blocking of CD59

We investigated the effects of suppression of complement activation at C3 level and inhibition of C5a on acute synovitis in rats. Acute synovitis was induced in Wistar rats by intra-articular (i.a.) injection into one knee of 0.3 mg of MoAb 6D1 (anti-rat CD59 antibody). In the treatment groups, soluble CR1 (sCR1) or C5a receptor (C5aR) antagonist was administered intra-articularly or intravenously and effects on the course of the acute synovitis were monitored. Synovitis induced by 6D1 was characterized by joint swelling, thickening of synovial tissue, cellular infiltration and deposition of membrane attack complex (MAC) on the synovial surface. Neither inflammatory change nor MAC deposition was found in rats which received an i.a. injection of sCR1 to suppress complement activity in the joint. Intra-articular injection of sCR1 did not reduce plasma complement activity. Intravenous administration of sCR1 suppressed plasma complement activity but had no effect on the course of the arthritis and synovitis with MAC deposition was observed. Neither i.a. nor i.v. injection of C5aR antagonist had any suppressive effects on inflammatory change or MAC deposition in synovium. The data show that inflammatory change induced by 6D1 was mediated by local complement activation and was not accompanied by systemic complement activation. C5a generation was not responsible for the observed inflammation, suggesting that other complement activation products, possibly MAC, mediate the inflammatory change observed in this model of acute synovitis in rats.

Loxosceles intermedia spider envenomation induces activation of an endogenous metalloproteinase, resulting in cleavage of glycophorins from the erythrocyte surface and facilitating complement-mediated lysis

Loxosceles is the most venomous spider in Brazil, and envenomation causes dermonecrosis and complement (C)-dependent intravascular hemolysis. The authors studied the mechanism of induction of C-induced hemolysis. Purified Loxosceles toxins rendered human erythrocytes susceptible to lysis by human C but did not have an effect on the E-bound C-regulators DAF, CR1, or CD59. However, incubation with venom toxins caused cleavage of glycophorin from the erythrocyte (E) surface, facilitating C activation and hemolysis. The results suggest that glycophorin is an important factor in the protection of E against homologous C. Cleavage of glycophorin (GP) A, GPB, and GPC occurred at sites close to the membrane but could not be accomplished using purified GPA and purified toxins, demonstrating that cleavage was not an effect of a direct proteolytic action of the Loxosceles toxins on the glycophorins. Inhibition of the cleavage of glycophorins induced by Loxosceles venom was achieved with 1,10-phenanthroline. The authors propose that the sphingomyelinase activity of the toxins induces activation of an endogenous metalloproteinase, which then cleaves glycophorins. They observed the transfer of C-dependent hemolysis to other cells, suggesting that the Loxosceles toxins can act on multiple cells. This observation can explain the extent of hemolysis observed in patients after envenomation. Identification of the mechanism of induction of susceptibility to C-mediated lysis after Loxosceles envenomation opens up the possibility of the development of an effective therapeutic strategy. (Blood. 2000;95:683-691)

Complement mediated cell death is associated with DNA fragmentation

In this study, we demonstrate for the first time that complement attack of target cells, in the presence of suitably high levels of serum, can induce the oligonucleosomal DNA fragmentation characteristic of apoptosis. This phenomenon requires membrane permeabilisation induced by formation of the complete membrane attack complex and relies on physiologically relevant levels of serum. TUNEL analysis detected complement mediated DNA fragmentation as early as 30 min after the addition of serum and electron microscopy confirmed that chromatin became condensed after complement attack. Various experiments implicate serum DNase I as the mediator of this DNA fragmentation. Intriguingly, membrane permeability induced by melittin gave rise to similar serum dependent DNA fragmentation. The implications of these results for the study of apoptosis in vitro and in vivo are discussed.

Echoviruses and coxsackie B viruses that use human decay-accelerating factor (DAF) as a receptor do not bind the rodent analogues of DAF

Many serotypes of echovirus (EV) and Coxsackie B virus (CBV) bind human decay-accelerating factor (DAF) and use it as a receptor for infection. Analogues for DAF have been isolated from mice and rats and characterized; these analogues have amino acid identities to human DAF of approximately 60%. EV serotypes 3, 6', 7, 11-13, and 29 and CBV serotypes 1, 3, and 5 caused hemagglutination of human erythrocytes but not rat or mouse erythrocytes, suggesting failure to bind rodent DAF. To confirm this evidence, radiolabeled viruses were incubated with transfected Chinese hamster ovary (CHO) cells that were abundantly expressing each type of DAF. Only cells that expressed human DAF bound virus. Although binding of EV and CBV was specific for human DAF, complement inhibition by DAF expressed in CHO cells was similar for each analogue.

Soluble complement receptor one (sCR1) inhibits the development and progression of rat collagen-induced arthritis

We set out to determine whether inhibition of complement using sCR1 could influence the development and progression of collagen arthritis in the Lewis rat. Collagen arthritis was successfully established in the Lewis rat, using a novel immunization schedule. In separate experiments, cobra venom factor (CVF) and sCR1 were used to achieve systemic complement inhibition. Their respective effects on disease onset and on the progression of established disease compared with saline-treated control animals was explored. Arthritis was assessed by measurement of clinical score, paw diameter and paw volume. Complement inhibition using either CVF or sCR1, prior to the onset of clinical signs of inflammation, delayed the development of disease. CVF was ineffective in the treatment of established disease, whereas sCR1 delayed the progression of disease in affected joints and prevented the recruitment of further joints while the animals were complement-depleted. In the control saline-treated groups the disease continued to progress relentlessly. We conclude that complement activation is important in the initiation and maintenance of inflammation in collagen arthritis. The potent disease-modulating effect of sCR1 provides persuasive evidence that specific complement inhibiting agents may be an effective approach to the treatment of inflammatory joint diseases

Production and functional analysis of rat CD59 and chimeric CD59-Crry as active soluble proteins in Pichia pastoris

Crry (CR1-related gene/protein) is a rodent complement regulator that inhibits C3 convertases. CD59 is a conserved protein inhibitor active towards C8 and C9. We have previously produced rat Crry as a recombinant soluble (rs) protein in Pichia pastoris. In this study we produced functionally active rat rsCD59 and a chimeric rsCD59-Crry protein in P. pastoris. The GPI anchor addition site of rat CD59 (Asn-79) was replaced either by a stop codon to produce rsCD59, or with the sequence of the first five short consensus repeats of Crry to produce rsCD59-Crry. Proteins were generated by fermentation and purified by affinity chromatography on an anti-CD59 column. In a standard classical pathway haemolysis assay, all three rs proteins had inhibitory activity, with 50% inhibition at 0.5 microM (rsCrry and rsCD59-Crry) and 4.4 microM (rsCD59). In an assay examining inhibition of C5b-9, in which C5b-7 was first formed, followed by purified C8 and C9, rsCD59 and rsCD59-Crry were active with 50% inhibition at 0.8 microM (rsCD59-Crry) and 1.3 microM (rsCD59). The degree of inhibition was independent of whether the C8 and C9 were of rat or human origin. Therefore, we have produced rsCD59 and rsCD59-Crry in P. pastoris. The rsCD59 retains its inhibitory activity towards C5b-9, while rsCD59-Crry appears to have the combined activities of Crry and CD59. In a haemolytic assay, the inclusion of CD59 to Crry is of no additional benefit to Crry, which may illustrate the overall importance of the C3 convertase step. Yet, inclusion of Crry to CD59 increases the potency of CD59 towards C5b-9.

Development of adenovirus vectors encoding rat complement regulators for use in therapy in rodent models of inflammatory diseases

C activation has been implicated in the pathogenesis of numerous inflammatory human diseases and disease models. A therapy based on C inhibition might therefore be of benefit to reduce inflammation and ameliorate disease. C inhibition in vivo can be accomplished by the delivery of soluble recombinant C regulators either systemically or directly to a target site, but effects are transitory. We have developed a strategy for the efficient delivery of the membrane-bound rat C inhibitors, CD59, Crry, and decay-accelerating factor (DAF), using replication-deficient adenovirus vectors with the intention of treating rat models of disease in which C is implicated. The adenovirus recombinants(RAd), RAdCD59, RAdCrry, and RAdDAF, respectively, have been tested for expression and function of the transgene in vitro. Infection of human fetal foreskin fibroblasts resulted in high levels of expression of each of the rat inhibitors. The constructs were also tested for inhibition of rat C-mediated cell lysis and C3b deposition. In a cell lysis assay, each inhibited to varying degrees of efficiency in the order RAdCD59 = RAdDAF > RAdCrry. In a C3b deposition assay, RAdDAF caused a greater reduction in C3b deposition than RAdCrry and RAdCD59 was ineffective. These agents, individually or in combination, provide the tools for testing the effects of prolonged inhibition of C at a target site on the progress of experimental models of disease.

Differential expression of individual complement regulators in the brain and choroid plexus

Membrane bound regulators of complement (C) control the system at key points during activation. To determine whether C regulators were expressed in the central nervous system, temporal cortex, and choroid plexus, tissues from eight adult humans were obtained at postmortem and surgery. Tissue was taken fresh for total RNA isolation, snap freezing, or processing in paraffin wax for immunocytochemistry and in situ hybridization. Immunocytochemistry of temporal cortex using anti-CD59 stained microglia intensely; astrocytes and neurons weakly. Microglia were unequivocally stained with anti-membrane cofactor protein (MCP) whereas staining on astrocytes and neurons was weak. Decay accelerating factor (DAF) was strongly expressed by microglia but weakly by astrocytes. Neurons expressed neither DAF nor complement receptor 1 (CR1). CR1 was also absent on astrocytes and microglia. The choroid plexus epithelium revealed intense apical staining with antibodies to CD59, less strongly with anti-MCP and weakly with anti-DAF. CR1 was detected only on phagocytic Kolmer cells in the choroid plexus. Reverse transcriptase-polymerase chain reaction revealed CD59, MCP, and to a lesser degree, DAF mRNA both in the choroid plexus and temporal cortex. CR1 mRNA was detected in choroid plexus samples only. Digoxigenin-UTP-labeled riboprobes to all four membrane regulators were used for in situ hybridization. DAF, MCP, and CD59 mRNA were expressed by epithelial cells of the choroid plexus and CR1 mRNA was found only in Kolmer cells. In the temporal cortex, MCP and CD59 mRNA were expressed by glia and at low level by neurons, but DAF was not detected. Previous studies have suggested that C produced in inflamed brains in conditions such as Alzheimer's and Huntington's diseases can be specifically toxic to neurons. The demonstration herein that neurons express only very low levels of CD59 and MCP and lack both CR1 and DAF might explain their susceptibility to C damage.

Role of complement regulatory membrane proteins in ischaemia-reperfusion injury of rat gastric mucosa

BACKGROUND

The role of complement in ischaemia-reperfusion injury has not been well investigated. 5I2 is a monoclonal antibody (mAb) directed against a rat membrane inhibitor of the C3 convertase step, which is the rat counterpart of mouse Crry/p65. 6D1 is a mAb against rat CD59 which inhibits the formation of membrane attack complexes.

METHODS

We visualized the tissue distribution of these membrane inhibitors in rat gastrointestinal tract by immunohistochemical staining with the appropriate mAb. Then, we tested the hypothesis that complement regulatory proteins protect rat gastric mucosa against ischaemia-reperfusion stress by using these mAbs. Gastric mucosal integrity was continuously monitored by measuring the blood-to-lumen clearance of [51Cr]-labelled ethylenediaminetetraacetic acid (EDTA) under control conditions, during ischaemia and after reperfusion.

RESULTS

Rat 6D1 and 5I2 antigens were both widely distributed and predominantly expressed on smooth muscle and endothelial cells in gastrointestinal tracts. Blockade of complement regulatory proteins with 5I2 and 6D1 mAbs resulted in a significant increase in [51Cr]-EDTA clearance after reperfusion.

CONCLUSIONS

These findings support the hypothesis that endogenous complement regulatory proteins may act as important protective factors against ischaemia-reperfusion stress in rat gastric mucosa.

Increased complement biosynthesis by microglia and complement activation on neurons in Huntington's disease

In this study complement activation and biosynthesis have been analysed in the brains of Huntington's disease (HD) (n = 9) and normal (n = 3) individuals. In HD striatum, neurons, myelin and astrocytes were strongly stained with antibodies to C1q, C4, C3, iC3b-neoepitope and C9-neoepitope. In contrast, no staining for complement components was found in the normal striatum. Marked astrogliosis and microgliosis were observed in all HD caudate and the internal capsule samples but not in normal brain. RT-PCR analysis and in-situ hybridisation were carried out to determine whether complement was synthesised locally by activated glial cells. By RT-PCR, we found that complement activators of the classical pathway C1q C chain, C1r, C4, C3, as well as the complement regulators, C1 inhibitor, clusterin, MCP, DAF, CD59, were all expressed constitutively and at much higher level in HD brains compared to normal brain. Complement anaphylatoxin receptor mRNAs (C5a receptor and C3a receptor) were strongly expressed in HD caudate. In general, we found that the level of complement mRNA in normal control brains was from 2 to 5 fold lower compared to HD striatum. Using in-situ hybridisation, we confirmed that C3 mRNA and C9 mRNA were expressed by reactive microglia in HD internal capsule. We propose that complement produced locally by reactive microglia is activated on the membranes of neurons, contributing to neuronal necrosis but also to proinflammatory activities. Complement opsonins (iC3b) and anaphylatoxins (C3a, C5a) may be involved in the recruitment and stimulation of glial cells and phagocytes bearing specific complement receptors.

Induction of decay-accelerating factor by cytokines or the membrane-attack complex protects vascular endothelial cells against complement deposition

Vascular endothelium is continuously exposed to complement-mediated challenge, and this is enhanced during inflammation. Although the complement-regulatory proteins decay-accelerating factor (DAF), CD59, and membrane cofactor protein (MCP) protect endothelial cells (ECs) against complement-mediated injury, the control of their expression and relative contributions to vascular protection is unclear. We explored the hypothesis that mechanisms exist which induce upregulation of complement-regulatory proteins on ECs to maintain vascular function in inflammation. Tumor necrosis factor alpha (TNFalpha) and interferon gamma (IFNgamma) each increased DAF expression but not CD59 or MCP expression, and a combination of these cytokines was more potent than either alone. Cytokine-induced expression depended on increased DAF mRNA and de novo protein synthesis and was maximal by 72 hours. In addition, assembly of the membrane-attack complex (MAC) on ECs induced a 3-fold increase in DAF expression, and this was enhanced by cytokines. DAF upregulation was not inhibited by protein kinase C (PKC) antagonists. The increase in DAF was functionally relevant since it reduced complement 3 (C3) deposition by 40%, and this was inhibited by an anti-DAF monoclonal antibody. These observations indicate that upregulation of DAF expression by cytokines or MAC may represent an important feedback mechanism to maintain the integrity of the microvasculature during subacute and chronic inflammatory processes involving complement activation.

Complement activation and inhibition in experimental models of arthritis

Complement activation has been implicated as a pathological process in a number of inflammatory and autoimmune disorders including chronic rheumatoid arthritis (RA). Animal models of experimental arthritis have been widely used to investigate the pathogenesis of RA and also in the development of novel therapies. Many of these models are complement-dependent and both incidence and progression of disease can be influenced by complement inhibition. In certain situations, local inhibition is of greater therapeutic benefit than systemic decomplementation. An increasing awareness and availability of a wide range of naturally occurring complement regulatory proteins can now offer a more targeted approach to complement inhibition while the availability of novel engineering strategies has also improved the efficiency of this process. The success of complement inhibition in the experimental models described should offer a novel therapeutic approach to the treatment of human inflammatory arthritis.

Molecular cloning, expression and characterization of the rat analogue of human membrane cofactor protein (MCP/CD46)

In humans, host cells are protected from homologous complement by membrane proteins encoded in the regulators of complement activation (RCA) gene cluster. These include complement receptor 1 (CR1), decay-accelerating factor (DAF, CD55) and membrane cofactor protein (MCP, CD46). In mouse and rat a single membrane inhibitor, Crry, appeared to perform the functions of both DAF and MCP and was proposed to be the functional analogue of both. Recently, however, murine homologues of DAF and MCP have been identified, prompting a search for the rat counterparts. We have described the identification of rat DAF and here describe the cloning of rat MCP from cDNA and genomic libraries, using a probe based on the mouse MCP cDNA sequence. The domain structure for rat MCP was identical to that of mouse MCP with four short consensus repeats (SCRs) followed by a STP domain, transmembrane segment and cytoplasmic tail. Overall identity of rat and mouse MCP was 77% at the amino acid level and 88% at the nucleotide level. Northern blot analysis from a range of tissues indicated that high-level expression was limited to the testis, although expression in other tissues was detected using reverse transcription-polymerase chain reaction. Rat MCP mRNA localized to Sertoli cells and spermatogonia in seminiferous tubules by in situ hybridization, but was absent in mature sperm. In cofactor assays utilizing human factor I, a recombinant soluble form of rat MCP catalysed cleavage of human C3ma.

Distribution of membrane cofactor protein (MCP/CD46) on pig tissues. Relevance To xenotransplantation

Membrane cofactor protein (MCP; CD46) is a 50-60 000 MW glycoprotein, expressed on a wide variety of cells and tissues in man, which plays an important role in regulating complement activation. Human MCP has also been shown to be the receptor for measles virus. We have recently identified the pig analogue of MCP and demonstrated that pig MCP has cofactor activity for factor I-mediated cleavage of C3b when these components are derived either from pig or human. As a consequence, pig MCP is an efficient regulator of the classic and alternative pathways of human and pig complement. In order to define the potential importance of MCP in protecting against complement activation in the pig, we have conducted a comprehensive survey of its distribution in pig cells and organs. As in humans, MCP in the pig is broadly and abundantly distributed. Pig MCP is highly expressed on all circulating cells, including erythrocytes, in contrast to its absence on human erythrocytes. Multiple isoforms of MCP are found on cells and in tissues, probably representing products of alternative splicing analogous to those found in man. MCP is abundantly expressed throughout all tissues examined with particularly strong staining on the vascular endothelium. Connective tissue elements within liver and testis are also strongly stained by anti-pig MCP antibodies. Pig MCP is expressed only weakly on skeletal muscle cells and expression is absent from smooth muscle cells in the lung and vessel walls, sites at which human MCP is expressed. Of particular note, MCP is not expressed in B-cell areas of the germinal centres of lymph nodes.

Molecular and functional analysis of mouse decay accelerating factor (CD55)

Molecular cloning of mouse decay accelerating factor (DAF; CD55) predicted two forms of the molecule, one transmembrane (TM) and the other glycosylphosphatidylinositol (GPI)-anchored; these are encoded by separate genes termed Daf-GPI and Daf-TM. In the present study several additional isoforms of mouse DAF, generated by alternative splicing from these genes, are described. Northern-blot analysis of RNA and reverse transcriptase-PCR from various tissues indicated that spleen and testis expressed high levels of DAF, which comprised several species. These species were cloned and sequence analysis revealed various novel forms in addition to those previously reported. Two novel forms were derived from the Daf-TM gene but the transmembrane sequence defined previously was replaced by a unique GPI-anchor addition sequence; one clone also had part of the serine/threonine/proline (STP) region deleted. A third clone, encoding a transmembrane protein, was also derived from this gene but the entire STP region was deleted. A fourth clone, derived from the Daf-GPI gene, contained a novel C-terminal sequence, suggestive of a secreted form of the protein. Two DAF cDNAs (TM and GPI-anchored) were stably expressed in Chinese hamster ovary cells. When these cells were attacked with mouse or rat complement and analysed for C3b deposition, DAF-transfected cells had greatly reduced C3b deposition compared with controls. Transfection with DAF also conferred protection from complement in a cell-lysis assay, and a soluble, recombinant form of mouse DAF inhibited complement in a haemolytic assay.

Regulation of the complement membrane attack pathway

Complement activation, triggered through classic, alternative, or lectin pathways of activation, leads to activation of a final common reaction sequence, the membrane attack pathway, in which five soluble plasma proteins assemble into a multimolecular complex that inserts into and through the membrane, creating a functional pore, the membrane attack complex. The active products of membrane attack are the anaphylactic and chemotactic fragment C5a and the membrane attack complex itself. These active products are important in immune defense but also carry the potential to damage host cells. Regulation of the membrane attack pathway is essential to protect host cells from damage at sites of C activation, and several protective systems have evolved to achieve this in vivo. Nevertheless, in disease these protective systems may be overwhelmed, and the availability of agents that specifically inhibit the membrane attack pathway might be of considerable therapeutic benefit. In this article I first describe the membrane attack pathway, its active products, and its role in disease. Second, I discuss systems operating to prevent damage to host cells by membrane attack, the regulatory proteins and activities that form the core of the article. Finally, I describe recent developments in the production of therapeutic agents with the capacity to inhibit membrane attack pathway.

Tissue distribution of the rat analogue of decay-accelerating factor

In humans, decay-accelerating factor (DAF) is a widely distributed, cell-bound inhibitor of the complement activation enzymes and plays a key role in regulating complement activation, preventing the generation of anaphylotoxins and opsonins, and protecting against complement-mediated lysis. Rodent analogues of DAF have recently been identified, providing a new avenue for the analysis of function. Rat DAF was cloned in our laboratory. Here we describe the generation of monoclonal antibodies (mAbs) against rat DAF, using transfected cells as immunogen, and their use in the analysis of the distribution of DAF in the rat by flow cytometry, Western blot analysis and immunohistochemistry. One of the mAbs was found to block the complement inhibitory function of rat DAF, offering the prospect of neutralization of DAF function in vivo. The antibodies have also been used for purification of DAF from rat erythrocytes by affinity chromatography. Rat DAF purified in this manner was similar in molecular mass to human DAF. The purified protein incorporated into lipid membranes, confirming the presence of a glycolipid anchor, and incorporated protein strongly inhibited the rat C3 convertase. Rat DAF was strongly expressed on endothelia throughout the animal and was also present in most tissues and organs. DAF expression was weak or absent in the brain and on circulating and spleen-resident T cells. Strong DAF expression observed in the kidney was restricted to the glomerulus and Bowman's capsule. DAF expression in the testis was found only in association with the later stages of spermatogenesis.

Evolution of the pelvic pouch procedure at one institution: the first 100 cases

BACKGROUND

Total extirpation of the colon with pelvic pouch formation, and the avoidance of a permanent stoma, continues to pose a challenge for better results, both technically and functionally. The aims of this study were to investigate the first 100 pelvic ileal-pouch procedures, assessing changes in surgical technique, their relationship to morbidity and long-term outcome, and compare this to the few large international series.

METHODS

Between 1984 and 1997, 100 patients had a pelvic J-shaped ileal-pouch formed, 58 two-stage and 42 three-stage procedures. Fifty had a hand-sewn pouch-anal anastomosis and 50 a double-stapled anastomosis. Seventy-three were for ulcerative colitis, five for indeterminate colitis, 20 for familial adenomatous polyposis (FAP), one for multiple primary colorectal cancers, and one for constipation.

RESULTS

After a median follow-up of 68 months, 97% of patients still have a functioning pouch. There were two postoperative deaths (one after-pouch formation and one after-stoma closure). Morbidity occurred in 52 patients, including three patients with pouch leaks and three pouch-anal anastomosis leaks (6% leak rate), 27% with a small bowel obstruction (2% early, 20% late, 5% both), a 19% anal stricture rate, and a 9% pouchitis rate. Three pouches have been removed (all for Crohn's disease). Median number of bowel movements per day was six, with 85% of patients reporting a good quality of life. Patients following a double-stapled procedure have less anal seepage and improved continence over those with a hand-sewn ileal pouch-anal anastomosis.

CONCLUSIONS

Despite high morbidity rates, pelvic pouch formation provides satisfactory long-term results for patients requiring total proctocolectomy, with functional results and morbidity rates comparable to larger overseas series.

Efficient generation of monoclonal antibodies against surface-expressed proteins by hyperexpression in rodent cells

The generation of antibodies is one of the first requirements in the characterisation of a newly cloned protein. However, this requires expression and purification of the protein in sufficient yield and purity for immunisation of animals and screening of fusion wells. Even with the development of highly efficient protocols based upon incorporation of specific peptide tags, this can be a tedious and time-consuming process. In an effort to improve the speed and efficiency of obtaining antibodies reactive with newly cloned proteins we have developed an approach based upon the expression of the protein at high level in cell lines originating from the species to be used for immunisation. To illustrate this approach we describe the generation of antibodies against two recently cloned proteins that are normally expressed at the membrane, the rat and mouse analogues of human decay accelerating factor (DAF; CD55). However, the strategy is applicable not only to membrane proteins but also to other proteins which can be expressed on the cell membrane by incorporating at the carboxy terminus the signal sequence for glycosyl phosphatidylinositol (GPI) anchor addition derived from DAF or another GPI-anchored protein. The strategy also permits rapid and efficient screening using flow cytometry on expressing cells.