Effects of Long-Term Supplementation of Bovine Colostrum on the Immune System in Young Female Basketball Players. Randomized Trial

An intensive physical exercise program could lead to a decrease in immune system function. Effects of long-term supplementation of bovine colostrum on the response of immune function on physical exercise test in athletes were examined. Twenty-seven elite female basketball players (age 16–19) were randomly assigned to either an experimental group or a control group. Eventually, n = 11 athletes completed intervention in the experimental group (3.2 g bovine colostrum orally twice a day for 24 weeks), while n = 9 athletes in the control group were given a placebo. Before the supplementation, after 3 and 6 months, subjects performed the physical exercise stress test. Before, just after, and 3 h after physical exercise testing, blood was drawn and immune system indicators were examined. Plasma interleukin (IL)-1alpha, IL-2, IL-10, IL-13, tumor necrosis factor (TNF) alpha, creatine kinase (CK MM), immunoglobulin G (IgG), insulin-like growth factor 1 (IGF1), and WBC, lymphocyte (LYM), monocyte (MON), and granulocyte (GRA) were measured. A statistically significant change in IL-10 in response to the exercise program during the supplementation period in both groups was observed (p = 0.01). However, the results of the rest of the comparisons were statistically insignificant (p > 0.05). Contrary to our initial hypothesis, there were no significant effects of bovine supplementation on the dynamics of immune system function indicators.

Diagnosis and Management of Immune-Mediated Myopathies

Immune-mediated myopathies (IMMs) are a heterogeneous group of acquired muscle disorders characterized by muscle weakness, elevated creatine kinase levels, and myopathic electromyographic findings. Most IMMs feature the presence of inflammatory infiltrates in muscle. However, the inflammatory exudate may be absent. Indeed, necrotizing autoimmune myopathy (NAM), also called immune-mediated necrotizing myopathy, is characterized by a necrotizing pathologic process with no or minimal inflammation in muscle. The recent discovery of antibodies associated with specific subtypes of autoimmune myopathies has played a major role in characterizing these diseases. Although diagnostic criteria and classification of IMMs currently are under revision, on the basis of the clinical and muscle histopathologic findings, IMMs can be differentiated as NAM, inclusion body myositis (IBM), dermatomyositis, polymyositis, and nonspecific myositis. Because of recent developments in the field of NAM and IBM and the controversies around polymyositis, this review will focus on NAM, IBM, and dermatomyositis.

Antibody cross-reactivity and the viral aetiology of type 1 diabetes

Type 1 diabetes (T1D) is caused by the destruction of insulin-producing pancreatic β cells by the patient's immune system. While the underlying genetics and immunopathology are fairly well characterized, the environmental trigger remains unidentified. Numerous studies have centred on the role of enteroviruses as aetiological factors that could initiate or accelerate T1D development. The most convincing evidence to date consists of an array of reports documenting the presence of enteroviral nucleic acids in peripheral blood at diagnosis. A prominent hypothesis is that enteroviruses may infect the pancreatic islets and thus be responsible for the islet-specific up-regulation of MHC class I that is commonly observed, possibly enabling T cell recognition and cytotoxicity. Past immunohistochemical studies have indeed shown that antibodies binding the enteroviral capsid protein VP1 preferentially stain the pancreatic β cells from diabetic individuals. New data now indicate that the VP1 antibody used in these studies cross-reacts with mitochondrial proteins.

Monoclonal antibody FsC-47 against carp sperm creatine kinase

The enzyme creatine kinase (CK) plays a key role in energy homeostasis of cells with high and fluctuating energy requirements. As for spermatozoa, the activity of phosphocreatine shuttle, which directs energy from the mitochondria to sites of ATP consumption, is dependent on individual species. High activities of CK are observed in spermatozoa of nonvertebrate, fish, and birds, contrary to the low-level CK activity in mammalian spermatozoa. A new monoclonal antibody (MAb) to carp sperm creatine kinase was prepared. This antibody is applicable to large-scale immunochemical techniques. In this study, it was applied to the study of carp sperm motility, and the evaluation of the influence of CK on the quality and fertilization ability of carp spermatozoa.

Immunological and physical comparison of monomeric and dimeric phosphagen kinases: Some evolutionary implications

The antigenic and physical properties of several representative invertebrate phosphagen kinases have been examined in order to further characterize the relationship between taxonomic assignment, quaternary protein structure and evolution of this class of enzymes. Antibodies against dimeric arginine kinase from the sea cucumber cross-reacted with dimeric arginine kinase purified from sea urchin eggs, but failed to react with extracts from any species known to contain monomeric arginine kinase. However, strong immunoreactivity was observed when antibodies against purified dimeric arginine kinase were reacted with pure creatine kinase from the human muscle (CK-MM) and brain (CK-BB) as well as extracts from several species known to contain dimeric creatine kinase. Of particular interest with regard to evolution of the phosphagen kinases, we confirm the presence of creatine kinase activity in the very primitive sponge Tethya aurnatium and detect a reaction with antibodies against dimeric, but not monomeric, arginine kinase. This observation is consistent with recent studies of phosphagen kinase evolution. Substrate utilization was very specific with creatine kinase using only creatine. Arginine kinase catalyzed phosphorylation of arginine but enzymes from several species could also phosphorylate canavanine. No activities were detected with d-arginine. Isoelectric points, evaluated for several pure arginine kinases suggest that generally the monomeric forms are more acidic than the dimeric proteins. Heat inactivation of arginine kinase in several species indicated a wide range of stabilities, which did not appear to be correlated with quaternary structure, but rather distinguished by the organism's environment. On the other hand, homodimeric arginine kinase proteins from species inhabiting disparate environments are sufficiently homologous to form a catalytically active hybrid.

Development of monoclonal antibodies against creatine kinase MB2

An increase of creatine kinase MB (CKMB) in serum has long been used as a marker for acute myocardial infarction (AMI). It is important with an early diagnosis and since the amount of the CKMB2 isoform rises above reference levels much earlier than the total creatine kinase amount, quantification of CKMB isoforms could be a feasible alternative for early analysis. The two CKMB isoforms differ by only one C-terminal lysine residue, which makes it difficult to separate one from the other. To overcome this problem, monoclonal antibodies were produced using unique peptides as antigen in hybridoma technology. Two peptides with 16 and 15 amino acids corresponding to the C-terminal end of the M-subunits of CKMB2 and CKMB1, respectively, were conjugated to keyhole limpet hemocyanin and used as antigens. Sixteen different monoclonal antibodies to these peptides were obtained and characterized. Their specificity was analyzed by immunoassay and 10 of the antibodies showed cross-reactive binding to creatine kinase. Surface plasmon resonance based biosensor analysis was used to determine affinity and kinetics towards the peptides and the epitopes of four of the antibodies were studied by means of phage display. Some of these antibodies have binding properties that might qualify them for use in the establishment of procedures allowing early diagnosis of AMI.

Exercise immunology: a skeletal muscle perspective

When exploring the possible mechanisms by which adaptation to physical exercise can occur, the immune system appears to be a likely candidate of importance, because physical exercise will exert both systemic and local effects on the immune system. This review will focus on the immune system in the perspective of skeletal muscle tissue adaptation to physical exercise. The involvement of circulating and tissue bound leukocytes, cytokines, hormones and growth factors will be discussed. A few new hypotheses are presented: 1) The primary mechanism governing skeletal muscle adaptation to physical exercise is suggested to be of non-inflammatory origin; 2) it is suggested that IL-10 may function as one of the signals transmitted by skeletal muscle cells when substrate levels are low; 3) creatine kinase could have immuno-modulatory actions, thereby serving as a messenger molecule between skeletal muscles and the immune system. Based on the intricate and complex array of events governing life and death in other cells types, a simple explanation of the issues of skeletal muscle development, regeneration and adaptation is unlikely. There are large individual differences in the immune response to the same relative or absolute exercise intensity, suggesting that interpreting the average effect of exercise on a group of individuals may not reveal the cause and effect of any given immunological variable. More sophisticated analyses of collected data is suggested in future studies and perhaps some re-evaluation of existing data is also needed. If we can understand the mechanisms behind muscle adaptation, we can also optimize training programs and athletic performance.

Isoenzyme-directed selection and characterization of anti-creatine kinase single chain Fv antibodies from a human phage display library

Epitopes differing among isoenzymes of creatine kinase (CK) are apparently limited in number and poorly immunogenic in vivo. Especially for the BB-CK isoenzyme, very few monoclonal antibodies (mAb) are available. Here, we use in vitro selection with a synthetic human phage display antibody library and develop isoenzyme competition and peptide panning strategies to obtain human single chain Fv (scFv) antibodies against specific CK isoenzymes. We isolated and characterized seven scFv clones that recognize native as well as denatured cytosolic BB-CK in ELISA, immunoblot, immunofluorescence histochemistry and surface plasmon resonance (SPR) spectroscopy. To a variable but minor degree, they also react with cytosolic MM-CK, but not with mitochondrial CK isoenzymes. Epitope mapping revealed that the scFv antibodies recognize different BB-CK epitopes, including the N-terminus and the isoenzyme-specific box, a highly conserved sequence of unknown function for which no mAb were available so far. With a K(D) of 3.5-9.6 x 10(-7) M, the isolated scFv compare favorably with mouse mAb and may overcome certain of their limitations. Our results demonstrate the advantages of in vitro antibody selection for the generation of isoenzyme-specific antibodies.

Designing gene therapy vectors: avoiding immune responses by using tissue-specific promoters

Attempts to correct genetic disorders by gene therapy have been hindered by various problems including unwanted immune responses against the gene product. It has been shown that immune responses with DNA vaccines after i.m. injection of antigen-encoding plasmid DNA are primed solely by professional antigen-presenting cells (APC), even though myocytes are the primary type of cell transfected. This possibly involves direct transfection of some APC in regional lymph nodes draining the injected muscle. Here we have used plasmid DNA vaccines that express hepatitis B surface antigen (HBsAg) to evaluate the possibility of abrogating these immune responses by use of a tissue-specific promoter that does not drive expression in APC. We show that HBsAg-specific humoral or cell-mediated responses are not induced in mice when the muscle-specific human muscle creatine kinase promoter is used in place of the ubiquitous cytomegaloviral promoter to drive expression of HBsAg. This may have significance in the field of gene therapy where one aims to achieve stable expression of the desired gene product without interference from the host immune response.

Expression of mouse anticreatine kinase (MAK33) monoclonal antibody in the yeast Hansenula polymorpha

The methylotrophic yeast Hansenula polymorpha HM1-39 (ura 3 and leu 2) was used as a host strain for the expression of the Fab fragment of the MAK33 monoclonal antibody. The MAK33 antibody reacts specifically with creatine kinase-M. The cDNA of kappa and gamma chains were inserted between the FMD or MOX promoter and the MOX terminator within the expression plasmids. In addition, the secretion signal sequence of the mating factor-alpha (prepro segment) and a fragment from glucoamylase with its secretion signal peptide, were also inserted in the expression plasmids for efficient secretion and production of the MAK33 monoclonal antibody. The co-expression of kappa and gamma chains was achieved by double transformation with kappa and then with gamma chain-expressing plasmids. The cells of H. polymorpha HM1-39 showed high mitotic stability and both uracil+ and leucine+ phenotypic stability after double transformation. Northern analysis showed a high rate of transcription of either kappa or gamma chain mRNA but not both, when the cells were grown in an induction medium. Protein analysis of double-transformed cells showed the monomers of the MAK33 antibody (kappa and gamma chains) were not assembled into a heterodimeric functional form. The expressed proteins of light and heavy chains represent about 11-12% of total cell protein and are found more inside than outside the cell. The expressed monomers show antigen-binding affinity in the Ouchterlony diffusion test; and the binding activity exhibited by cell-free extract was more than that of the cell culture supernatant.

The crystal structure of the fab fragment of the monoclonal antibody MAK33. Implications for folding and interaction with the chaperone bip

The Fab fragment of the murine monoclonal antibody, MAK33, directed against human creatine kinase of the muscle-type, was crystallized and the three-dimensional structure was determined to 2.9 A. The antigen-binding surface of MAK33 shows a convex overall shape typical for immunoglobulins binding large antigens. The structure allows us to analyze the environment of cis-prolyl-peptide bonds whose isomerization is of key importance in the folding process. These residues seem to be involved with not only domain stability but also seem to play a role in the association of heavy and light chains, reinforcing the importance of beta-strand recognition in antibody assembly. The structure also allows the localization of segments of primary sequence postulated to represent binding sites for the ER-specific chaperone BiP within the context of the entire Fab fragment. These sequences are found primarily in beta-strands that are necessary for interactions between the individual domains.

Posttransplantation relapse of FSGS is characterized by glomerular epithelial cell transdifferentiation

This study examined six cases of idiopathic nephrotic syndrome with primary lesions of focal segmental glomerulosclerosis (FSGS) that relapsed after renal transplantation. The glomerular lesions comprised the cellular, the collapsing, and the scar variants of FSGS and showed shedding of large round cells into Bowman's space and within the tubular lumens. Immunohistochemistry and confocal laser microscopy carried out on kidneys with FSGS relapse disclosed several phenomena. (1) Some podocytes that expressed podocalyxin, synaptopodin, and glomerular epithelial protein-1 were detached from the tuft and were free in the urinary space. (2) In the cellular variant, most podocytes had lost podocyte-specific epitopes (podocalyxin, synaptopodin, glomerular epithelial protein-1, Wilm's tumor protein-1, complement receptor-1, and vimentin). In the scar variant, these podocyte markers were absent from cobblestone-like epithelial cells and from pseudotubules. (3) Podocytes had acquired expression of various cytokeratins (CK; identified by the AE1/AE3, C2562, CK22, and AEL-KS2 monoclonal antibodies) that were not found in the podocytes of control glomeruli. Parietal epithelial cells expressed AE1/AE3 CK that were faintly, if ever, found on the parietal epithelial cells of normal glomeruli. (4) Numerous cells located at the periphery of the tuft or free in Bowman's space and within tubular lumens expressed macrophagic epitopes (identified by PGM1 [CD68], HAM56, and 25F9 monoclonal antibodies). These macrophage-like cells expressed the activation epitopes HLA-DR and CD16. (5) A number of these cells coexpressed podocalyxin + AE1/AE3 CK, podocalyxin + CD68, and CD68 + AE1/AE3. These findings suggest that in primary FSGS relapsing on transplanted kidneys, some "dysregulated" podocytes, occasionally some parietal epithelial cells, and possibly some tubular epithelial cells undergo a process of transdifferentiation. This process of transdifferentiation was especially striking in podocytes that acquired macrophagic and CK epitopes that are absent from normal adult and fetal podocytes.

Structure of an intermediate in the unfolding of creatine kinase

The homodimeric muscle isoform of creatine kinase (MM-CK) unfolds on exposure to low levels of guanidinium chloride (GdmCl) to yield a partly folded monomeric intermediate. Those regions of MM-CK that experience local unfolding were previously identified through an extensive study of antibody accessibility and protease sensitivity. Since these studies were completed, the coordinates of the rabbit isoform (MM-CK) were released. In light of this, we have determined the minimum changes to this structure required to explain our data on protease and epitope accessibility in the intermediate. We propose that the observed changes occur through (a) disruption of the monomer-monomer interface during dissociation, (b) separation and/ or unfolding of domains or subdomains, and (c) the partial unfolding of solvent-exposed helices. The proposed structure for the intermediate is consistent both with current models of unfolding intermediates and the results of independent studies pertaining to the unfolding of creatine kinase. Proteins 2001;42:269-278.

Autoantibodies in the sera of patients with rheumatic heart disease: characterization of myocardial antigens by two-dimensional immunoblotting and N-terminal sequence analysis

The concept of antigenic mimicry in autoimmune diseases such as rheumatic fever has been under investigation for decades and the range of cross-reactive tissue antigens for streptococcal-induced antibodies identified in rheumatic heart disease is still expanding. To identify heart tissue-reactive antigens which may be implicated in the secondary immunopathogenesis of rheumatic fever, sera from 56 patients with acute rheumatic heart disease were probed in two-dimensional Western blots for reactivity against heart tissue antigens. After two-dimensional immunoblot analysis, proteins were submitted to N-terminal amino acid sequence analysis. This analysis identified creatine kinase, two mitochondrial proteins and, at a low level, various stress proteins as cross-reactive myocardial antigens. Therefore, in addition to myosin, creatine kinase may represent another major antigen for autoreactive antibodies in rheumatic heart disease. Mitochondrial proteins have been implicated in the pathogenesis of inflammatory heart disease for some years, and in this study we have identified two mitochondrial proteins as relevant antigens in rheumatic heart disease.

Multiple-analyte fluoroimmunoassay using an integrated optical waveguide sensor

A silicon oxynitride integrated optical waveguide was used to evanescently excite fluorescence from a multianalyte sensor surface in a rapid, sandwich immunoassay format. Multiple analyte immunoassay (MAIA) results for two sets of three different analytes, one employing polyclonal and the other monoclonal capture antibodies, were compared with results for identical analytes performed in a single-analyte immunoassay (SAIA) format. The MAIA protocol was applied in both phosphate-buffered saline and simulated serum solutions. Point-to-point correlation values between the MAIA and SAIA results varied widely for the polyclonal antibodies (R2 = 0.42-0.98) and were acceptable for the monoclonal antibodies (R2 = 0.93-0.99). Differences in calculated receptor affinities were also evident with polyclonal antibodies, but not so with monoclonal antibodies. Polyclonal antibody capture layers tended to demonstrate departure from ideal receptor-ligand binding while monoclonal antibodies generally displayed monovalent binding. A third set of three antibodies, specific for three cardiac proteins routinely used to categorize myocardial infarction, were also evaluated with the two assay protocols. MAIA responses, over clinically significant ranges for creatin kinase MB, cardiac troponin I, and myoglobin agreed well with responses generated with SAIA protocols (R2 = 0.97-0.99).

Oxidative myocytes of heart and skeletal muscle express abundant sarcomeric mitochondrial creatine kinase

Sarcomeric mitochondrial creatine kinase catalyzes the reversible transfer of a high energy phosphate between ATP and creatine. To study cellular distribution of the kinase, we performed immunocytochemical studies using a peptide antiserum specific for the kinase protein. Our results demonstrated that the sarcomeric mitochondrial creatine kinase gene is abundantly expressed in heart and skeletal muscle, with no protein detected in other tissues examined, including brain, lung, liver, spleen, kidney, bladder, testis, stomach, intestine, and colon. RNA blot study showed that there is no detectable expression of the kinase mRNA in the thymus gland. In heart and skeletal muscle, the kinase protein is expressed in atrial and ventricular cardiomyocytes and a subpopulation of skeletal myofibres. In skeletal muscle, fast myosin heavy chain co-localization studies demonstrated that the sarcomeric mitochondrial creatine kinase is highly expressed in type 1, slow-oxidative and type 2A, fast-oxidative-glycolytic myofibres. We conclude that the kinase gene is abundantly expressed in oxidative myocytes of heart and skeletal muscle and may contribute to oxidative capacity of these cells.

Adriamycin-induced changes of creatine kinase activity in vivo and in cardiomyocyte culture

Adriamycin (ADM) is an anthracycline anti-neoplastic agent, whose clinical effectiveness is limited by severe side effects, including cardiotoxicity. The toxic effects of ADM are likely to be the consequence of the generation of free radicals. This study demonstrates that ADM induces significant changes in the activity of the oxidative sensitive enzyme creatine kinase (CK) in the heart in vivo and in a cardiomyocyte culture model. The changes observed are likely to reflect the ability of ADM to damage the plasma membrane of cardiac cells and to induce the direct inactivation of CK. The role for ADM-derived free radicals is one of the possible mechanisms for the CK inactivation observed during the ADM treatment.

Accumulation pattern of IgG antibodies and Fab fragments in transgenic Arabidopsis thaliana plants

For the further optimization of antibody expression in plants, it is essential to determine the final accumulation sites of plant-made antibodies. Previously, we have shown that, upon secretion, IgG antibodies and Fab fragments can be detected in the intercellular spaces of leaf mesophyll cells of transgenic Arabidopsis thaliana plants. However, immunofluorescence microscopy showed that this is probably not their final accumulation site. In leaves, IgG and Fab fragments accumulate also at the interior side of the epidermal cell layers and in xylem vessels. These accumulation sites correspond with the leaf regions where water of the transpiration stream is entering a space impermeable to the proteins or where water is evaporating. In roots, plant-made Fab fragments accumulate in intercellular spaces of cortex cells, in the cytoplasm of pericycle and, to a lesser extent, endodermis cells, and in cells of the vascular cylinder. In other words, antibody accumulation occurs at the sites where water passes on its radial pathway towards and within the vascular bundle. Taken together, our results suggest that, upon secretion of plant-made antibodies or Fab fragments, a large proportion of these proteins are transported in the apoplast of A. thaliana, possibly by the water flow in the transpiration stream.

Myofibrillar interaction of cytosolic creatine kinase (CK) isoenzymes: allocation of N-terminal binding epitope in MM-CK and BB-CK

The molecular origin of the isoenzyme-specific interaction of cytosolic creatine kinase isoenzymes, muscle-type creatine kinase and brain-type creatine kinase, with myofibrillar structures has been studied by confocal microscopy in an functional in situ binding assay with chemically skinned, unfixed skeletal muscle fibers using wild-type and chimeric creatine kinase isoproteins. The specific interaction of both wild-type isoforms with the sarcomeric structure resulted in a stable, isoform-characteristic labeling pattern with muscle-type creatine kinase bound exclusively and tightly to the sarcomeric M-band while brain-type creatine kinase was confined to the I-band region. Chimeric proteins of both muscle-type and brain-type creatine kinases were constructed to localize the corresponding binding domain(s). Exchanged domains included the N-terminal part (residues 1–234), the region containing an isoenzyme ‘diagnostic box’ (residues 235–285) and the C-terminal part (residues 286–380). The purified recombinant proteins were all fully intact and enzymatically active. All chimeric proteins containing the N-terminal region (amino acid 1–234) of muscle-type or brain-type creatine kinase were always specifically targeted to the sarcomeric M-band or I-band, respectively. We therefore propose that the relevant epitope(s), determining the isoenzyme-specific targeting in skeletal muscle, are entirely located within the N-terminal regions of both cytosolic creatine kinase isoforms.

A novel autoantibody in paraneoplastic sensory-dominant neuropathy reacts with brain-type creatine kinase

We have previously reported on a novel autoantibody in a patient with paraneoplastic sensory-dominant neuropathy. This autoantibody immunostains the rat primary sensory system and reacts with a 47 kDa protein on immunoblotting. Here, we report on the isolation from rat spinal cord of a molecule that is recognized by this autoantibody. By ammonium sulfate cut and gel filtration, affinity and ion exchange chromatographies, the immunoreactive protein was purified to homogeneity and identified as brain-type creatine kinase (B-CK). Our study revealed that the autoantibody of the patient reacted with B-CK in the primary sensory system.

Terminal groups in Starburst dendrimers: activation and reactions with proteins

Starburst dendrimers are novel nanoscopic synthetic polymers of defined molecular mass and geometry. These macromolecules, available in commercial quantities, contain methyl carboxylate and primary amino-terminal groups. The presence of these groups on any macromolecule limits its usefulness especially in cases where, for specific modulation of the properties of biologically active molecules, covalent bond formation is desirable between the biologically active molecules and the macromolecule. This paper describes activation of the surface groups of Starburst dendrimers for incorporation of a number of reactive electrophilic and nucleophilic groups and utilization of these reactive groups in formation of covalent bonds between dendrimers and alkaline phosphatase. The protein-dendrimer complexes have been reacted further with the Fab' fragment of an anti-creatine kinase MB isoenzyme antibody to form multifunctional dendrimer reagents. The enzymatic and immunochemical properties of these protein-dendrimer reagents have been evaluated by an immunoassay system. Nucleophilic thiols and electrophilic phenyliodoacetamido, iodoacetamido, and epoxy groups have been incorporated into amino-terminal dendrimers by their reactions with appropriate heterobifunctional reagents. Two independent sets of reactions have been used to prepare the reactive N-hydroxysuccinimidyl esters from dendrimers containing the terminal carboxyl groups. Quantitation of the reactive groups has been carried out by direct titration of these activated dendrimers and the products obtained by reactions of these dendrimers with small molecules and proteins.

Removal of endotoxin from recombinant protein preparations

OBJECTIVES

To develop an effective method to remove endotoxin from large scale E. coli recombinant protein purifications.

DESIGN AND METHODS

Triton X-114 phase separation, affinity chromatography utilizing immobilized polymyxin B or immobilized histidine, were used to remove endotoxin from purified preparations of recombinant CK-BB, CK-MB, CK-MM, myoglobin, and cardiac troponin I. Endotoxin levels were measured by a Limulus Amebocyte Lysate gel-clot assay. The immunoactivity of these protein preparations was determined by BIAcore analysis using a panel of in-house generated monoclonal antibodies and by a Stratus Fluorometric Analyzer. In the case of troponin I, the BIAcore was also utilized to measure troponin C interactions.

RESULTS

Phase separation with Triton X-114 was the most effective method in reducing the amount of endotoxin present in the protein preparations compared to either polymyxin B or histidine affinity chromatography. With Triton X-114, the reduction in endotoxin levels was greater than 99% and recovery of the proteins after endotoxin removal was greater than 90%. All three procedures for removing endotoxin had no deleterious effects on the immunoactivity of majority proteins when tested with a panel of monoclonal antibodies. Troponin I also retained its ability to bind to troponin C in the presence of Ca2+. Recombinant CK-BB and CK-MM which were expressed in the soluble fraction of E. coli cell lysates, contained significantly higher endotoxin levels than recombinant CK-MB, myoglobin and cardiac troponin I which were expressed in the form of inclusion bodies.

CONCLUSION

Of the three methods tested, Triton X-114 phase separation was the most effective way of removing endotoxin from recombinant proteins.

Inhibition of ubiquitous mitochondrial creatine kinase expression in HeLa cells by an antisense oligodeoxynucleotide

Antisense strategy has been used to inhibit the synthesis of the human ubiquitous mitochondrial creatine kinase (Mi-CK) in HeLa cells. Indeed, elevated levels of Mi-CK in the serum of some cancer patients seem to be an adverse pronostic indicator (for refs see Wallimann T and Hemmer W, Mol Cell Biochem 133/134: 193-220, 1994). A phosphorothioate oligonucleotide, complementary to the second intron-exon splice junction site of the human ubiquitous Mi-CK pre-mRNA was shown to inhibit Mi-CK synthesis by 80% without modifying F1-ATPase beta subunit expression or hampering HeLa cell growth. This inhibition was correlated to a decrease of the Mi-CK mRNA level that could be determined quantitatively after amplification of reverse transcription products (RT) in the presence of varying concentrations of internal standard competitors. This study also demonstrated that the Mi-CK mRNA copy number was much lower in HeLa cells than that of the cytosolic creatine kinase isoform, B-CK. The antisense-induced decrease in Mi-CK mRNA and protein level influenced neither the expression of B-CK which uses up the phosphocreatine produced by Mi-CK during the phosphocreatine shuttle, nor that of another nuclear encoded mitochondrial gene, the F1-ATPase subunit which provides ATP to Mi-CK. In conclusion, an elevated Mi-CK expression is not required for cancer cell growth and therefore, Mi-CK is not a significant limiting factor for the growth of the cancer cells which contain it. In addition, a decrease in Mi-CK synthesis does not induce a change in the expression of mitochondrial F1-ATPase which provides ATP to Mi-CK or in the expression of cytosolic B-CK which is involved together with Mi-CK in the phosphocreatine shuttle. Therefore, the use of the phosphocreatine shuttle as a process mandatory for the active growth of some cancer cells is questioned.

Regulation of creatine kinase isoenzymes in human placenta during early, mid-, and late gestation

OBJECTIVE

Creatine kinase (CK) isoenzymes play an important role in cellular energy transduction. Two isoenzymes of creatine kinase, ubiquitous mitochondrial creatine kinase (uMtCK) and cytosolic brain creatine kinase (BCK), are postulated to form the creatine phosphate (CP) shuttle, in which creatine serves to transport high-energy phosphate from the mitochondria to its site of utilization. Coordinate regulation of these genes is essential for efficient energy transduction. We examined human CK isoenzyme regulation in placentas during all three trimesters of gestation to define the mRNA and protein expression patterns of uMtCK and BCK and to test the CP shuttle hypothesis.

METHODS

Placental samples were collected from a total of 26 patients from the first, second, and third trimesters. Total RNA and protein were prepared from each sample and quantified. Quantitative RNA analysis was performed by gel electrophoresis and dot blot techniques using isoenzyme-specific human cDNA probes for uMtCK and BCK. Protein expression of uMtCK and BCK was examined by Western blot analysis using isoenzyme-specific antibodies to uMtCK and BCK.

RESULTS

Analysis of RNA demonstrated the coordinate expression of uMtCK and BCK mRNAs in human placenta, with peak expression of both in the term placentas. Western blot analysis demonstrated coordinate expression of uMtCK and BCK proteins in the first and second trimesters, but not in the term placenta. Expression levels of uMtCK and BCK proteins were not consistent with their respective mRNA levels in the term placenta.

CONCLUSION

Expression of uMtCK and BCK in human placenta is highly regulated, and post-transcriptional regulation of uMtCK and BCK expression occurs in the term placenta. The coordinate regulation of uMtCK and BCK in human placenta supports the CP shuttle hypothesis. This analysis demonstrates that human placenta has high energy needs that can change rapidly; thus, a functioning CP shuttle may be important in the maintenance and termination of pregnancy.

Antigen-antibody binding kinetics for biosensors. Changes in the fractal dimension (surface roughness) and in the binding rate coefficient

The diffusion-limited binding kinetics of antigen in solution to antibody immobilized on a biosensor surface is analyzed within a fractal framework. Changes in the fractal dimension, Df observed are in the same and in the reverse directions as the forward binding rate coefficient k. For example, an increase in the concentration of the isoenzyme human creatine kinase isoenzyme MB form (CK-MB) (antigen) solution from 0.1 to 50 ng/mL and bound to anti-CK-MB antibody immobilized on fused silica fiber rods leads to increases in the fractal dimension Df from 0.294 to 0.5080, and in the forward binding rate coefficient k from 0.1194 to 9.716, respectively. The error in the fractal dimension Df decreases with an increase in the CK-MB isoenzyme concentration in solution. An increase in the concentration of human chorionic gonadotrophin (hCG) in solution from 4000 to 6000 mIU/mL hCG and bound to anti-hCG antibody immobilized on a fluorescence capillary fill device leads to a decrease in the fractal dimension Df from 2.6806 to 2.6164, and to an increase in the forward binding rate coefficient k from 3.571 to 4.033, respectively. The different examples analyzed and presented together indicate one means by which the forward binding rate coefficient k may be controlled, that is by changing the fractal dimension or the "disorder' on the surface. The analysis should assist in helping to improve the stability, the sensitivity, and the response time of biosensors.

Characterization of relevant membrane antigens by two-dimensional immunoblot and n-terminal sequence analysis in patients with myocarditis

In myocarditis an antigen-specific immune response to cardiac epitopes has been demonstrated by several investigators. In 25 patients with histologically proven myocarditis, autoantibodies to cardiac tissue were observed in 65% by immunofluorescence assay. By immunoblot analysis 46% of sera reacted with cardiac tissue. These antibodies were preferentially directed against proteins with molecular weights of 43 and 67 kDa. Many of these antibodies have been demonstrated to be cytolytic to isolated cardiocytes in vitro. However, their corresponding antigens on heart muscle cells still remains unclear. To characterize the epitopes recognized by the autoantibodies, isoelectric focusing followed by SDS-PAGE was used to separate the complex mixture of proteins from human heart. Immunoblot analysis of antigens revealed proteins in the range of 30-67 kDa at isoelectric points of 6.5-8.5 to be of particular interest. Five of these proteins were identified by immunoblot analysis and two were identified by n-terminal sequence analysis (Edman Degradation) as creatine kinase and a sarcomeric isoenzyme. As creatine kinase is an intracellularly located enzyme, the pathogenetic role of the autoantibodies directed against it remains to be elucidated further.

An immunochemical mass assay for the direct measurement of creatine kinase MB2

The isoforms of CK-MB have recently received attention as potential biochemical markers for the early diagnosis of an acute myocardial infarction. A sensitive (analytical sensitivity = 0.2 ng/ml) immunochemical mass assay for the direct measurement of the CK-MB2 isoform has been developed by us. This assay utilizes a specific monoclonal capture antibody directed against the B-subunit of CK-MB and a specific monoclonal antibody conjugate directed against the CK-M + lysine subunit. Owing to the lack of a World Health Organization standard for CK-MB, the percent CK-MB2 values had to be normalized by determining both CK-MB and CK-MB2 in assays which differ only in the specificity of the anti-CK-M conjugate. Thus, a related CK-MB immunochemical mass assay utilizing the identical capture antibody and a specific monoclonal antibody conjugate directed against the CK-M subunit was also developed. Analytical sensitivities of the CK-MB and CK-MB2 assays were determined to be 0.5 ng/ml and 0.2 ng/ml, respectively. Both CK-MB and CK-MB2 levels were determined in 46 hospitalized non-AMI patients and 35 non-hospitalized normal patients. Of the 46 hospitalized non-AMI patients (mean age = 70), 26 percent had either CK-MB and/or CK-MB2 values below the level of sensitivity of the CK-MB or CK-MB2 isoform assays. For patients with CK-MB values between 0.5 ng/ml and 2.99 ng/ml, the percent CK-MB2 values ranged from 35 percent to 97 percent. For patients with CK-MB values between 3.0 ng/ml and 6.5 ng/ml, the percent CK-MB2 values ranged from 23 percent to 72 percent. Similar results were obtained for the non-hospitalized group. This assay appears to be useful in determining the clinical utility of CK-MB2.

Tissue- and cell-specific distribution of creatine kinase B: a new and highly specific monoclonal antibody for use in immunohistochemistry

A synthetic 17-mer peptide corresponding to an unique sequence in the amino-terminal region of human creatine kinase B was used to raise a new and highly B-subunit-specific monoclonal antibody, CK-BYK/21E10. We show here that the monoclonal antibody is suitable for immunohistochemistry of unfixed frozen sections as well as formaldehyde- or Bouin-fixed, paraffin-embedded sections of human, rabbit, and mouse tissues. Moreover, in the study of cell- and tissue-specific distribution patterns, parallel Western blot analysis and immunoelectron microscopy is possible using this antibody. Our analyses demonstrate that creatine kinase B expression is restricted to a specific subset of cell types in various tissues. In brain, the B-subunit was found only in neurocytes, but not in glia cells. High expression was also observed in inner segments of photoreceptor cells and the outer plexiform layer of the retina, in the parietal cells of the stomach and in gut enterocytes, gallbladder and epithelial cells of the urogenital system. The possible roles of the creatine kinase/phosphocreatine-ATP system in these tissues are discussed.

Location of an epitope shared by Alzheimer's amyloid peptide and brain creatine kinase using a newly developed monoclonal antibody

Amyloid plaques, composed mainly by a peptide termed A4-amyloid, derived by proteolytic processing from the amyloid precursor protein (APP), are a hallmark in the brain of Alzheimer's disease patients. We have prepared a collection of monoclonal antibodies as tools to study APP expression and proteolysis in different systems. One of these, 5AH10, raised against residues 9-22 of A4-peptide, was selected for its ability to recognize only A4 subpeptides having the intact APP-secretase target sequence, as well as whole recombinant APP. By using synthetic subpeptides, we have located 5AH10 epitope between amino acids 15 and 22 of A4. In addition, 5AH10 showed a strong immunoreactivity to a 47 kDa protein present in rat brain extracts, that was identified as the B (brain specific) subunit of creatine kinase by immunochemical data and direct N-terminal sequencing. The cross-reaction observed is most probably due to a high degree of sequence identity between amino acids 15 to 22 of A4 peptide and amino acids 9 to 16 of rat B creatine kinase. 5AH10 did not recognize the muscle specific isoform (M subunit) of rat creatine kinase, nor the B subunit of human and rabbit creatine kinase, suggesting that glutamine at first position of the epitope is essential for antigen recognition by 5AH10.

Association of antibody chains at different stages of folding: prolyl isomerization occurs after formation of quaternary structure

The folding pathways of multi-domain proteins are still poorly understood due to the complexity of the reaction involving domain folding, association and, in many cases, prolyl cis/trans isomerization. Here, we have established a kinetic model for the folding of the Fab fragment of the antibody MAK 33 with intact disulfide bonds. Folding of the hetero-dimeric protein from the completely denatured, oxidized state comprises the pairwise association of the two domains of each chain with those of the partner protein. Both the reactivation of the Fab fragment in which the two constituent polypeptide chains were covalently linked via a cystine bond (Fab) and that of a mutant lacking this covalent linkage (Fab/-cys) were monitored by ELISA. Folding of the Fab fragment is a slow process, which can be described by a single exponential term. The kinetic phase reflects a folding step after the association of the two chains. The same reaction was detected in the folding of Fab/-cys but an additional rate-limiting step is involved that is due to a unimolecular step in the folding of the isolated light chain. This implies that, during Fab reactivation, Fd associates with the light chain at the stage of an earlier folding intermediate, thus eliminating the additional slow folding step of the light chain observed with Fab/-cys. Both in Fab and Fab/-cys renaturation, the folding reaction after association is determined by prolyl isomerization. Therefore, at least four different association-competent folding intermediates have to be postulated according to the folding stage of light chain and the configuration of at least one prolyl-peptide bond. Using the different substrate specificities of cyclophilin and FK506 binding protein, we have obtained evidence that Pro159 within the Fd fragment may be responsible for the observed slow folding phase after association, although three other proline residues adopt a cis configuration in the native protein. Furthermore, the data suggest that in the case of the Fab fragment, association is a prerequisite for cis/trans isomerization of prolyl peptide bonds, implying that the quaternary but not the tertiary structure determines the cis-configuration of the prolyl residue in Fd involved in the rate-limiting folding reaction.

Immunoreactive creatine kinase-MB and creatine kinase isozyme concentrations during treatment of hypothyroid patients

Using a highly sensitive enzyme immunoassay (EIA) system, we determined creatine kinase isozymes, namely creatine kinase-MB and creatine kinase-MM, in sera of patients suffering from primary hypothyroidism with concomitant signs of myocardial affections before and during treatment. After oral administration of L-thyroxine, the augmented mass concentrations of serum creatine kinase-MB and creatine kinase-MM, and the increased catalytic activity concentrations of serum total creatine kinase and creatine kinase-MB gradually decreased in inverse proportion to the increased concentrations of serum triiodothyronine (T3) and thyroxine (T4). By the 6th to 8th week after treatment, the elevated levels of serum total creatine kinase and creatine kinase-MB catalytic activity concentrations (assayed by a routine method) and serum creatine kinase-MM mass concentrations (assayed by EIA) declined to normal values, while serum T3, T4, and thyroid stimulating hormone attained normal values. Serum creatine kinase-MB mass concentrations (assayed by EIA), however, still remained at the higher level, without complete recovery from myocardial damage, as shown by electrocardiogram (ECG). These data indicate that metabolic distortion still exists in the myocardium, as revealed by the high creatine kinase-MB mass concentration, especially as assayed by EIA, even though the plasma levels of thyroid hormones had returned to normal.

Chemical synthesis of bispecific monoclonal antibodies: potential advantages in immunoassay systems

To date, the applications of bispecific antibodies in immunoassay and immunocytochemical procedures have been directed at uniting two different biomolecules through the binding of epitopes on each respective substance. In this study, bispecific antibodies were constructed in which both binding sites were directed to two different epitopes of the same target molecule. Two types of bispecific antibody were constructed; a bivalent bispecific monoclonal antibody and multivalent bispecific polymers. The binding characteristics of each were investigated for changes in specificity and binding strength relative to 1:1 mixtures of parent antibodies. A bivalent bispecific antibody (BBA) was synthesised by the method of Glennie et al. (1985) from monoclonal antibodies recognising the 'M' or 'B' units of creatine kinase (CKMB). The BBA had enhanced specificity for CKMB with diminished recognition of CKMM and CKBB. A less tedious method of producing bispecific antibody involving heterobifunctional cross-linkage was used to produce multivalent bispecific antibodies (MBAs). Certain MBAs constructed to bind 'M' and 'B' units of CKMB demonstrated enhanced specificity and affinity for CKMB. MBAs were also produced to opposite ends of the 39 amino acid peptide adrenocorticotrophic hormone (ACTH). One of these demonstrated an enhanced affinity of 41-fold. We conclude that while conventional synthesis of bispecific bivalent antibodies is not a practical proposition for immunoassay development, antibodies with similar advantages can be produced with a simple method using the heterobifunctional cross-linker. The production of certain bispecific antibody combinations appears to enhance the formation of antibody-antigen matrices conferring higher binding affinities than can be achieved with an antibody mixture alone.

Effects of CaBP2, the rat analog of ERp72, and of CaBP1 on the refolding of denatured reduced proteins. Comparison with protein disulfide isomerase

It has been shown previously that CaBP2, the rat analog of the murine protein ERp72, and CaBP1, the rat analogue of the hamster protein P5, represent members of the protein disulfide isomerase (PDI) family and are able to catalyze the reduction of insulin in the presence of various reductants (Nguyen Van et al., 1993). We have now examined the abilities of CaBP2 and CaBP1 to catalyze the renaturation of denatured reduced model proteins. Both CaBP2 and CaBP1 catalyzed the reappearance of the biological activity of the denatured reduced Fab fragment of a monoclonal anti-human creatine phosphokinase antibody. The reaction rate was positively correlated with the amount of CaBP2 or CaBP1 and dependent on the GSH/GSSG ratio (maximum at GSH/GSSG = 1). Peptide prolyl-cis,trans-isomerase (PPI), which catalyzed some renaturation on its own, showed synergistic effects with PDI, CaBP2, and CaBP1. No synergistic effects could be observed when the combinations CaBP2 + PDI, CaBP1 + PDI, or CaBP2 + CaBP1 were tested. Variation of [Ca2+] between 0 and 1 mM did not have any effect on the rate or amount of renaturation catalyzed by CaBP2, CaBP1, or PDI, nor were these parameters affected by the simultaneous presence of BiP or grp94. Both CaBP2 and CaBP1 catalyzed also the renaturation of denatured reduced ribonuclease AIII in a way that depended on the amounts of CaBP2 or CaBP1 and on the redox potential of the redox system used (GSH/GSSG or CSH/CSSC). PPI alone had no effect on the rate of RNase AIII renaturation and did not significantly affect renaturation catalyzed by PDI, CaBP2, or CaBP1. PDI showed a moderate but significant synergism with CaBP2, and a strong synergism with CaBP1. The results indicate that both CaBP2 and CaBP1 can catalyze the formation of disulfide bonds and protein disulfide isomerization and may thus be involved in the folding of nascent proteins in the secretory pathway. This does not exclude the possibility of additional functions of these proteins in the pre-Golgi compartments.

[The diagnostic significance of creatine phosphokinase antibodies in the cardiac muscle in non-coronarogenic myocardial diseases]

Complement-binding antibodies to myocardium and cardiospecific enzyme creatine phosphokinase were determined in 25 patients with dilated cardiomyopathy, 29 patients with rheumatic myocarditis and in 21 patients with non-rheumatic myocarditis. The antibodies were shown to have diagnostic and differentiating significance in severe non-coronary heart disease associated with disordered systolic function of the heart.

Immunoelectron microscopic investigation of creatine kinase BB-isoenzyme after cerebral ischemia in gerbils

Alteration of creatine kinase BB-isoenzyme (CK-BB) was investigated in the vulnerable CA1 region of the hippocampus of ischemic and postischemic gerbil brains using immunoelectron microscopy. CK-BB existed in the neuronal perikarya, dendrites and axons as well as in astroglias in the normal gerbil brain. Immunocytochemical reaction products were associated with microtubules and polyribosomes. Propagation of ischemic and postischemic damage with disintegration of microtubules was observed in the dendro-somatic direction in neurons, which progressed in parallel with dispersion and loss of the immunocytochemical reaction for CK-BB in the dendroplasm. After reperfusion for longer than 24 h, CK-BB was also observed in the extracellular space. The present result supported the notion that loss of the immunohistochemical reaction for CK-BB which has been observed by light microscopy after cerebral ischemia, was at least partly due to dispersion of this enzyme caused by disintegration of microtubules and extracellular leakage of this enzyme, although other processes, including degradation of CK-BB per se, were also possible. The loss of CK-BB from the neuronal structure may delay the recovery from ischemic damage and may eventually lead to neuronal death.

Specificity of an immunochemical reagent for quantifying the isoforms of creatine kinase-MB

Fractionation of the creatine kinase-MB isoforms is promising for use in diagnosing acute myocardial infarction and for monitoring myocardial perfusion status after thrombolytic therapy. An immunochemical reagent intended for use in fractionating the MB1 and MB2 isoforms of creatine kinase-MB was examined before and after immunoextraction, qualitatively by visually examining electrophoresis separation of various MB1 and MB2 mixtures, and quantitatively by comparing the observed and predicted enzymatic activity of various MB1 and MB2 mixtures. Qualitatively the reagent showed greater reactivity for MB1 than for MB2, as demonstrated by a marked decrease in the MB1 electrophoretic region following immunoextraction. Quantitatively, the reagent consistently eliminated about 75% of MB1 activity; however, the assay also eliminated about 40% of MB2 activity from isoform mixtures. Although the performance of the immunochemical reagent was not ideal, the greater reactivity for MB1 may have clinical use.

The determination of cellular viability of hybridoma cells in microtitre plates: a colorimetric assay based on neutral red

A colorimetric assay utilising Neutral Red (C.I. 50040), a nuclear stain, was developed to determine the cellular viability of hybridoma cells in microtitre plates. A linear correlation (r = 0.99) was found to exist between the uptake of Neutral Red by viable cells and the viable cell count determined by Trypan blue exclusion test. The linearity stretched over the range of cell concentrations normal in batch cultures (2-30 x 10(4)/0.2 ml) with as little as +/- 6% intra-plate well-to-well variation and +/- 10.2% inter-assay variation. Microscopical examinations of viable hybridoma cells stained with Neutral Red showed that it was located in the nucleus. The possible bifunctional activity of the Neutral Red assay as a test for cellular viability and estimating the DNA content of hybridoma cells is discussed along with its application in a drug screening programme.

Hsp90 chaperones protein folding in vitro

The heat-shock protein Hsp90 is the most abundant constitutively expressed stress protein in the cytosol of eukaryotic cells, where it participates in the maturation of other proteins, modulation of protein activity in the case of hormone-free steroid receptors, and intracellular transport of some newly synthesized kinases. A feature of all these processes could be their dependence on the formation of protein structure. If Hsp90 is a molecular chaperone involved in maintaining a certain subset of cellular proteins in an inactive form, it should also be able to recognize and bind non-native proteins, thereby influencing their folding to the native state. Here we investigate whether Hsp90 can influence protein folding in vitro and show that Hsp90 suppresses the formation of protein aggregates by binding to the target proteins at a stoichiometry of one Hsp90 dimer to one or two substrate molecule(s). Furthermore, the yield of correctly folded and functional protein is increased significantly. The action of Hsp90 does not depend on the presence of nucleoside triphosphates, so it may be that Hsp90 uses a novel molecular mechanism to assist protein folding in vivo.

Multiple occurrence of macro creatine kinase in one family

We measured creatine kinase (CK, EC 2.7.3.2), CK-MB isoenzyme activity and mass concentration, and distribution of CK isoenzymes (by electrophoresis) in serum from five members of one family. The mother and two young children showed CK-IgG complexes in their sera. The concentration of the CK-IgG complexes in the children decreased over time, suggesting that the complex involved maternal IgG and had been transferred across the placenta from the mother to her children.

[Immunoinhibitory determination of CK-MM subbands by monoclonal antibody]

The measurement of CK-MM isoform by monoclonal antibody and its clinical application were summarized. The tissue type of CK-MM3 isoform was completely inhibited, MM2 isoform was about 57% and the serum type of CK-MM1 isoform was not inhibited by use of monoclonal antibody. This method enabled selective immunoinhibitory measurement of tissue type of CK-MM isoform. The heat lability and inhibition by EDTA suggested that it is a metal-depending enzyme. The analysis of MM isoform offers a promising alternate, non-invasive method to detect and follow up AMI and successful reperfusion. The MM3/MM1 ratio has been found to peak at about 2 to 6 hours, making it a quicker responding parameter to AMI than MM3 alone and significantly more responsive than the total CK or CK-MB. An MM3/MM1 ratio greater than 1.0 appears to be a practical cutoff point for detection of the pathological release of MM3 from tissue. Reperfusion therapy should be instituted within about 2 to 4 hours of AMI onset.

[Identification of a type 1 macrocreatine kinase]

A macrocreatine-kinase type 1 was identified by CK isoenzyme electrophoresis of a serum sample from a patient. Constituents of this enzyme complex were studied. The isoenzyme present in the macrocreatine-kinase was identified using immunoprecipitation with antibodies against the M subunit. Affinity chromatography then determined the type of the immunoglobulin bound to the CK isoenzyme. A protocol for studying macrocreatine-kinase type 1 compounds is proposed.

Creatine kinase MB measured by fluorometric enzyme immunoassay and immunochemiluminescence

Creatine kinase MB (CK-MB) was measured in serum by a fluorometric enzyme immunoassay on the Stratus analyzer and by an immunochemiluminometric assay using the Ciba Corning Magic Lite System. Both methods were standardized against purified CK-MB, with Stratus underestimating by 20 percent and Magic Lite overestimating by 28 percent. The assays proved sensitive and linear; however, at a CK-MB concentration of 7.0 micrograms per L, Stratus gave unacceptable inter-assay precision. No cross-reactivity was observed with CK-MM or CK-BB and elevated triglycerides, bilirubin, and hemoglobin did not interfere. Correlations with an immunoradiometric assay (Embria), using 522 samples, gave: Stratus = 0.999 (Embria) -3.3; r = 0.969, and Magic Lite = 1.225 (Embria) -3.03; r = 0.971. When using Magic Lite, results from 40 acute myocardial infarction (AMI) patients gave a mean CK-MB value of 93.8 micrograms per L (range: 9.2 to 428 micrograms per L) at the peak of enzyme release and a mean value of 69.6 micrograms per L (range: 6.7 to 319 micrograms per L) when using Stratus. Both methods proved to be highly sensitive and specific in the diagnosis of AMI; however, the need for standardization of CK-MB assays is stressed.