Complement C3d is not associated with axial spondyloarthritis and magnetic resonance imaging changes at the sacroiliac joint.

OBJECTIVE: To investigate the associations between complement C3d and inflammatory and structural changes by magnetic resonance imaging (MRI) at the sacroiliac joints (SIJ) suggestive of axial spondyloarthritis, according to the Assessment of SpondyloArthritis international Society (ASAS) criteria, in patients with low back pain. METHOD: This was a cross-sectional study of patients referred to the Spine Centre of Southern Denmark owing to unspecified low back pain (Spines of Southern Denmark cohort). The patients were divided into three groups: group 1: patients fulfilling the ASAS criteria for axial spondyloarthritis (axSpA, n = 96); group 2: patients with either a positive MRI of the SIJ and no spondyloarthritis features, or a negative MRI of the SIJ but positive human leucocyte antigen-B27 and one spondyloarthritis feature (non-axSpA, n = 38); group 3: patients with unspecified low back pain for > 3 months (control group, n = 82). Complement C3d was measured with double-decker rocket immunoelectrophoresis and evaluated in relation to the group division and baseline findings by SIJ MRI. RESULTS: In total, 184 C3d analyses were performed. The mean ± sd level of C3d was 33.8 ± 8.1 AU/mL. There were no differences in C3d levels between the three patient groups, mean values being: axSpA = 34.3 ± 7.9 AU/mL, non-axSpA = 33.5 ± 6.9 AU/mL, and controls = 33.4 ± 9.2 AU/mL. The level of C3d was not related to MRI findings. CONCLUSIONS: In these patients, complement C3d was not associated with active or structural SIJ changes on MRI suggestive of axial spondyloarthritis.

Cerebrospinal fluid biomarkers for predicting development of multiple sclerosis in acute optic neuritis: a population-based prospective cohort study.

BACKGROUND: Long-term outcome in multiple sclerosis (MS) depends on early treatment. In patients with acute optic neuritis (ON), an early inflammatory event, we investigated markers in cerebrospinal fluid (CSF), which may predict a diagnosis of MS. METHODS: Forty patients with acute ON were recruited in a prospective population-based cohort with median 29 months (range 19-41) of follow-up. Paired CSF and serum samples were taken within 14 days (range 2-38), prior to treatment. Prospectively, 16/40 patients were by a uniform algorithm diagnosed with MS (MS-ON) and 24 patients continued to manifest isolated ON (ION) during follow-up. Levels of cytokines and neurofilament light chain (NF-L) were measured at the onset of acute ON and compared to healthy controls (HC). Significance levels were corrected for multiple comparisons ("q"). The predictive value of biomarkers was determined with multivariable prediction models using nomograms. RESULTS: CSF TNF-α, IL-10, and CXCL13 levels were increased in MS-ON compared to those in ION patients (q = 0.021, 0.004, and 0.0006, respectively). MS-ON patients had increased CSF pleocytosis, IgG indices, and oligoclonal bands (OCBs) compared to ION (q = 0.0007, q = 0.0058, and q = 0.0021, respectively). CSF levels of IL-10, TNF-a, IL-17A, and CXCL13 in MS-ON patients correlated with leukocyte counts (r > 0.69 and p < 0.002) and IgG index (r > 0.55, p < 0.037). CSF NF-L levels were increased in ON patients compared to those in HC (q = 0.0077). In MS-ON, a progressive increase in NF-L levels was observed at 7 to 14 days after disease onset (r = 0.73, p < 0.0065). Receiver-operating characteristic (ROC) curves for two multivariable prediction models were generated, with IL-10, CXCL13, and NF-L in one ("candidate") and IgG index, OCB, and leukocytes in another ("routine"). Area under the curve was 0.89 [95% CI 0.77-1] and 0.86 [0.74-0.98], respectively. Predictions of the risk of MS diagnosis were illustrated by two nomograms. CONCLUSIONS: CSF TNF-α, IL-10, CXCL13, and NF-L levels were associated with the development of MS, suggesting that the inflammatory and neurodegenerative processes occurred early. Based on subsequent diagnosis, we observed a high predictive value of routine and candidate biomarkers in CSF for the development of MS in acute ON. The nomogram predictions may be useful in the diagnostic work-up of MS.

Associations between functional polymorphisms and response to biological treatment in Danish patients with psoriasis.

Biological agents including anti-tumor necrosis factor (anti-TNF; adalimumab, infliximab, etanercept) and anti-interleukin-12/13 (IL12/23; ustekinumab) are essential for treatment of patients with severe psoriasis. However, a significant proportion of the patients do not respond to a specific treatment. Pharmacogenetics might be a way to predict treatment response. Using a candidate gene approach, 62 mainly functional single-nucleotide polymorphisms (SNPs) in 44 different genes were evaluated in 478 Danish patients with psoriasis undergoing 376 series of anti-TNF treatment and 230 series of ustekinumab treatment. Associations between genetic variants and treatment outcomes (drug survival and Psoriasis Area Severity Index reduction) were assessed using logistic regression analyses (crude and adjusted for gender, age, psoriatic arthritis and previous treatment). After correction for multiple testing controlling the false discovery rate, six SNPs (IL1B (rs1143623, rs1143627), LY96 (rs11465996), TLR2 (rs11938228, rs4696480) and TLR9 (rs352139)) were associated with response to anti-TNF treatment and 4 SNPs (IL1B (rs1143623, rs1143627), TIRAP (rs8177374) and TLR5 (rs5744174)) were associated with response to ustekinumab treatment (q<0.20). The results suggest that genetic variants related to increased IL-1ß levels may be unfavorable when treating psoriasis with either anti-TNF or ustekinumab, whereas genetic variants related to high interferon-γ levels may be favorable when treating psoriasis with ustekinumab.

Prescribing practices and clinical predictors of glucose-lowering therapy within the first year in people with newly diagnosed Type 2 diabetes.

AIM: To examine prescribing practices and predictors of glucose-lowering therapy within the first year following diagnosis of Type 2 diabetes mellitus in a clinical care setting. METHODS: We followed people enrolled in the Danish Centre for Strategic Research in Type 2 Diabetes (DD2) cohort from outpatient hospital clinics and general practices throughout Denmark in 2010-2013. We used Poisson regression to compute age- and gender-adjusted risk ratios (RRs). RESULTS: Among 1158 new Type 2 diabetes mellitus patients, 302 (26%) did not receive glucose-lowering therapy within the first year, 723 (62%) received monotherapy [685 (95%) with metformin], and 133 (12%) received more than one drug. Predictors of receiving any vs. no therapy and combination vs. monotherapy were: age < 40 years [RR: 1.29 (95% CI: 1.16-1.44) and 3.60 (95% CI: 2.36-5.50)]; high Charlson Comorbidity Index [RRs: 1.20 (95% CI: 1.05-1.38) and 2.08 (95% CI: 1.16-3.72)]; central obesity [RRs: 1.23 (95% CI: 1.04-1.44) and 1.93 (95% CI: 0.76-4.94)]; fasting blood glucose of ≥ 7.5 mmol/l [RRs: 1.25 (95% CI: 1.10-1.42) and 1.94 (95% CI: 1.02-3.71)]; and HbA1c ≥ 59 mmol/mol (≥ 7.5%) [RR: 1.26 (95% CI: 1.20-1.32) and 2.86 (95% CI: 1.97-4.14)]. Weight gain ≥ 30 kg since age 20, lack of physical exercise and C-peptide of < 300 pmol/l also predicted therapy. CONCLUSIONS: Comorbidity, young age, central obesity and poor baseline glycaemic control are important predictors of therapy one year after Type 2 diabetes mellitus debut.

The predictive value of genetic variations in the vascular endothelial growth factor A gene in metastatic colorectal cancer.

Single-nucleotide polymorphisms (SNPs) in the vascular endothelial growth factor A (VEGF-A) gene may have clinical implications. The aim of this study was to investigate the possible predictive value of the VEGF-A SNPs, in patients with metastatic colorectal cancer (mCRC) treated with first-line capecitabine and oxaliplatin (XELOX). The study included 72 patients with mCRC. Genomic DNA was isolated from whole blood, and SNPs were analyzed by PCR. SNPs were correlated with response and progression-free survival (PFS). Haplotypes were estimated using the PHASE program. Response was observed in 21% of the patients with the -2578 CA genotype compared with 59% of the patients with CC+AA, P=0.002, in 26% of the patients with the -460 CT genotype compared with 57% with CC+TT, P=0.01, and in 27% of the patients with the +405 GC genotype compared with 54% with GG+CC, P=0.02. Two SNPs were significantly related to PFS. A haplotype with a significant relationship to response was identified. The results demonstrated obvious relationships between genetic variations in the VEGF-A gene and response to first-line XELOX in patients with mCRC, which translated to a significant difference in PFS. The results call for validation in a larger cohort of patients.

The relationship between serum vascular endothelial growth factor A and microsatellite instability in colorectal cancer.

AIM: It has been suggested that colorectal neoplasms with or without microsatellite instability (MSI) can stimulate angiogenesis in different ways. The vascular endothelial growth factor (VEGF) system is essential for the angiogenetic process and the growth of malignant tumours. The aim of this study was to analyse the relationship between serum VEGF-A and the MSI status of patients with colorectal cancer (CRC). METHOD: In the study, 249 patients with CRC were divided into a test cohort of 83 patients and a validation cohort of 166. MSI was determined using immunohistochemistry. Tumours lacking protein expression of any of the four mismatch repair genes (MLH1, PMS2, MSH2 or MSH6) were labelled as high MSI. The rest were considered to be microsatellite stable (MSS). The serum VEGF-A analyses were performed by ELISA. RESULTS: The tumours of 15 patients in the test cohort and 27 in the validation cohort were classified as MSI. In the test cohort, patients with an MSI tumour had a significantly higher median serum VEGF-A concentration [617 pg/ml (95% CI 445-863)], compared with patients with an MSS tumour, [317 pg/ml (95% CI 224-386)], P = 0.01. A similar relationship was confirmed in the validation cohort, P = 0.04. CONCLUSION: This study provides some evidence to suggest that patients with an MSI tumour have higher serum VEGF-A levels than patients with an MSS tumour. If further validated, these findings could be of importance when considering the effects of anti-VEGF-A treatment.

The predictive value of serum VEGF in multiresistant ovarian cancer patients treated with bevacizumab.

OBJECTIVE: Bevacizumab, a humanized monoclonal antibody against VEGF (vascular endothelial growth factor), has shown antitumor activity, but so far no biomarkers have been identified to predict outcome. The purpose of the present study was to investigate the efficacy of bevacizumab in patients with multiresistant ovarian cancer and, furthermore, to investigate the possible predictive value of serum VEGF, VEGFR1-2 and VEGF gene polymorphisms. METHODS: Patients received single-agent bevacizumab 10 mg/kg every 3 weeks. All patients were followed with CA 125 measurements and serum VEGF/VEGFR1-2 levels prior to each cycle. Endpoints were response rate (RR), progression-free survival (PFS) and overall survival (OS). RESULTS: Thirty-eight patients were included. All patients were heavily pre-treated with a median of five prior regimens. The median number of bevacizumab treatments was 4. Overall response rate was 30% according to CA 125 (GCIG criteria). Median PFS was 5.9 months (95% CI, 3.5-9.4) and median OS was 8.6 months (95% CI, 6.6-12.8). The VEGF serum level decreased during treatment in all patients. A low pre-treatment VEGF level was predictive to response. The median value was 540 pg/ml and divided the patients into two groups with a response rate of 60% and 0%, respectively (p=0.0007). The difference translated to a significant difference in PFS (p=0.047) and OS (p=0.01). VEGF gene polymorphisms -2578, -1154, -460, +405, +936 did not reveal any association with response or survival and the same applied to serum VEGFR1-2. CONCLUSIONS: Single agent bevacizumab has activity in ovarian cancer patients. Pre-treatment serum VEGF seems to have predictive value.

Highly sensitive quantification of optic neuritis intrathecal biomarker CXCL13.

BACKGROUND: Elevation of CXCL13, a key regulator of B-cell recruitment in cerebrospinal fluid (CSF) is implicated in multiple sclerosis (MS). OBJECTIVE: to evaluate if measurement of CXCL13 using a highly sensitive assay is of value in acute optic neuritis (ON) patients for the prediction of later MS. METHOD: CXCL13 was measured by Simoa in two independent treatment-naïve ON cohorts, a training cohort (TC, n = 33) originating from a population-based cohort, a validation cohort (VC, n = 30) consecutively collected following principles for population studies. Prospectively, 14/33 TC and 12/30 VC patients progressed to MS (MS-ON) while 19/33 TC and 18/30 VC patients, remained as isolated ON (ION). RESULTS: CXCL13 was detectable in all samples and were higher in ON compared with healthy controls (HC) (p = 0.012). In the TC, CSF levels in MS-ON were higher compared with ION patients and HC (p = 0.0001 and p<0.0001). In the VC, we confirmed the increase of CXCL13 in MS-ON compared to ION (p = 0.0091). Logistic regression analysis revealed an area under receiver operating characteristic curve of 0.83 [95% C.I: 0.73-0.93]. CONCLUSIONS: The highly sensitive CXCL13 Simoa assay demonstrated ability to identify ON patients and separate MS-ON from ION, and predictive diagnostic values indicates a promising potential of this assay.

Screening for methicillin-resistant Staphylococcus aureus in clinical swabs using a high-throughput real-time PCR-based method.

The presence of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals and the community is a serious problem. Accordingly, a comprehensive plan has been implemented in the County of Vejle, Denmark, to identify colonised and/or infected individuals and to control the spread of MRSA. Since 2005, all patients and healthcare personnel have been screened for MRSA colonisation, involving analysis of 300-400 samples daily. To deal with this number of samples, a PCR-based method customised for high-throughput analysis and a system for fast reporting of MRSA carrier status were developed. Swab samples were incubated overnight in a selective tryptone soya broth and were analysed by PCR the following day. Using this strategy, non-colonised individuals were identified within 24 h, while MRSA-positive samples were analysed further by traditional microbiological methods to determine the resistance pattern. This is a cost-effective approach, as the greatest expense in hospitals involves the isolation of patients of unknown MRSA status. The method was evaluated by testing 2194 clinical samples, with a sensitivity and specificity of 100% and 94%, respectively. The analytical sensitivity was 97%, with 161 of 166 different MRSA strains and isolates generating positive results according to PCR analysis. Using four control strains, the inter-assay variation was revealed to be a maximum of 2.6%, indicating good reproducibility.

Prediction of response to chemotherapy by ERCC1 immunohistochemistry and ERCC1 polymorphism in ovarian cancer.

The response of tumor cells to platinum-based chemotherapy involves DNA repair mechanisms. Excision repair cross-complementation group 1 (ercc1) is one of the leading genes involved in DNA repair, and several studies have linked ercc1 to platinum resistance in cell lines and in human cancers. A common single nucleotide polymorphism (SNP) of ercc1 at codon 118 has been proposed to impair ercc1 translation and reduce ERCC1 protein expression and consequently influence the response to platinum-based chemotherapy. The primary aim of the present study was to evaluate ERCC1 expression and ercc1 codon 118 polymorphism in epithelial ovarian cancer (EOC) and their possible predictive value in patients treated with platinum-based chemotherapy. Formalin-fixed, paraffin-embedded tissue sections from 159 patients with advanced EOC were used for immunohistochemistry. Ercc1 codon 118 SNP genotyping was performed by real-time polymerase chain reaction. ERCC1 protein overexpression was found in 37.7% of the tumors. The CA-125 response rate was 94.5% (52/55) in patients with ERCC1-negative tumors compared to 80% (36/45) in patients with ERCC1-positive tumors (P = 0.026, chi(2)). The T/T genotype (44%) signalized a better response to chemotherapy than C/C (15%) + C/T (41%) variants (P = 0.045, trend test). Patients with ERCC1-negative tumors appear to have significantly better response to platinum-based chemotherapy compared to patients with ERCC1-positive tumors, but the differences in response rates did not translate into differences in survival. In addition, the TT genotype seems to be favorable toward better response to platinum-based chemotherapy.

Omega-3 fatty acids inhibit an increase of proinflammatory cytokines in patients with active Crohn's disease compared with omega-6 fatty acids.

BACKGROUND: Crohn's disease is a chronic inflammatory condition affecting the gastrointestinal tract. Polyunsaturated omega-3 fatty acids given orally may reduce the secretion of proinflammatory cytokines and hereby downregulate the inflammatory process. AIM: To assess the effects of enteral fatty acids, in the form of Impact Powder (Novartis, Switzerland), as adjuvant therapy to corticosteroid treatment on the proinflammatory and anti-inflammatory cytokine profiles in patients with active Crohn's disease. METHODS: The proinflammatory and anti-inflammatory cytokines were measured in plasma from 31 patients with active Crohn's disease. Patients were randomized for oral intake of omega-3 fatty acid (3-Impact Powder) or omega-6 fatty acids (6-Impact Powder). Clinical and biochemical markers of inflammation were studied at baseline and after 5 and 9 weeks. RESULTS: Within the 3-Impact Powder group, no significant changes in concentrations of interleukin-6, interferon-gamma, monocyte chemoattractant protein-1, interleukin-2, interleukin-5 and interleukin-10, whereas a significant differences in concentration of interleukin-1beta and interleukin-4 were observed during therapy. Within the 6-Impact Powder group a significant changes in concentrations of interleukin-1beta, interleukin-6, interferon-gamma, monocyte chemoattractant protein-1, interleukin-2, interleukin-4, interleukin-5 and interleukin-10 were observed. CONCLUSIONS: The 3-Impact Powder showed immunomodulatory properties and might inhibit an increase of proinflammatory cytokines in contrast to the 6-Impact Powder.

Low normal alpha-1-antitrypsin serum concentrations and MZ-phenotype are associated with byssinosis and familial allergy in cotton mill workers.

Recent studies have shown a close association between byssinosis and airborne endotoxin concentrations. Endotoxin might induce byssinosis through the release of biochemical mediators as the broncheoalveolar surface. Alpha-1-antitrypsin (alpha-1-A) which neutralizes enzymes released by granulocytes is known to be important. This study evaluates the possible importance of alpha-1-A concentration and the heterozygosity (Pi-S and Pi-Z alleles), in the prevalence of byssinosis and familial allergy. 253 cotton workers were interviewed and clinically studied to identify persons with the cotton lung disease, byssinosis, and atopic disease. Serum was available for alpha-1-A concentration determination in 226 individuals, and for Pi phenotyping in 206. The overall prevalence of byssinosis was 30/226 (13%). In the group with alpha-1-A < or = 35 mumol l-1 the prevalence was 5/18 (28%), versus the prevalence 25/208 (12%) in the group with alpha-1-A > 35 mumol l-1 (p < 0.1, Fishers exact test). MZ phenotype was associated with an increased prevalence of byssinosis compared with the MM-group: 3/8 (38%) and 25/187 (13%), p < 0.1, Fishers exact test. An association between MZ-phenotype and familial allergy was found: 4/8 (50%) contra 23/187 (12%), p < 0.05, Fishers exact test. In a logistic regression model controlling for confounding by endotoxin, tobacco exposure, sex, and age, the odds ratio for byssinosis in the MZ-phenotype group was significantly elevated 5.8 (1.1-30.3). Odds ratio for familial allergy was also significantly elevated in the MZ-group 2.8 (1.3-5.9).(ABSTRACT TRUNCATED AT 250 WORDS)

A standardized method for quantitating the complement-mediated immune complex solubilizing capacity of human serum.

A standardized radioassay for measuring the complement-mediated immune complex solubilizing capacity (CMSC) and the initial kinetics of the solubilization (IKS) reaction is described. The total complement (C)-mediated solubilizing capacity was determined after incubation of diluted serum and 125I-BSA-anti-BSA. Percentage C-mediated solubilization (CMS) was measured after centrifugation by determining the distribution of radioactivity. The dependency of CMSC upon factors such as serum dilution and buffer system used, amount of IC added to serum, serum storage conditions and centrifugation conditions was investigated in order to optimize the assay. The CVt of the standardized assay was 0.10-0.17 depending upon the CMSC level measured. Treatment which inactivates C factors (heating), interferes with C activation (EDTA) or activates and consumes C components (zymosan) markedly reduces the CMSC. Preliminary investigation of pathological sera showed that both IKS and CMSC were clearly reduced in SLE sera. By contrast, rheumatoid arthritis sera exhibited normal IKS and only marginal reduction in CMSC.

Production of antibody against C3c epitopes which are inaccessible on native C3.

Anti-C3c antiserum was induced by immunizing rabbits with autologous erythrocytes coated with human C3b/C3bi. By absorption with human plasma this antiserum was rendered specific for C3c epitopes which are not expressed on native C3. This specificity may be analogous to that of immunoconglutinin.

Separation of human peripheral blood monocytes on continuous density gradients of polyvinylpyrrolidone-coated silica gel (Percoll).

A standardized, reproducible two-step method for separation of human peripheral blood monocytes on continuous Percoll gradients has been developed. The first step involves separation of mononuclear cell on Percoll of density 1.075 g/ml and the second step separation of monocytes from lymphocytes on a continuous Percoll gradient with a starting density of 1.075 g/ml for the formation of the gradient. The average yield during a 10 month period of daily routine use has been 74 +/- 17% (mean +/- 1 S.D.), and the average purity 63 +/- 10%. Ninety to 95% of the monocytes are viable after separation as judged from trypan blue exclusion and by ingestion of latex particles and sensitized sheep erythrocytes. The separation takes about 3 h and the total number of monocytes obtained from 40 ml of blood is in the range of 10-15 x 106. The procedure has been reliable with 3-4% separation failures, mainly due to bacterial or fungal growth in Percoll suspension or media. The contaminating cells are exclusively lymphocytes, predominantly T-lymphocytes (90-95%), when citrate is used as anticoagulant. Heparin can not be used as anticoagulant, as there appears to be a dose-dependent formation of thrombocyte aggregates which contaminate the monocytes, and result in poor separation.

Double-decker rocket immunoelectrophoresis for direct quantitation of complement C3 split products with C3d specificities in plasma.

A double-decker rocket immunoelectrophoresis (DD-RIE) method for direct quantitation of complement split products with C3d determinants in human plasma is described. The usefulness of the DD-RIE method for monitoring C3 activation has been assessed and compared with conventional crossed immunoelectrophoresis (CIE) for C3c determination in a patient with iatrogenic septic shock and patients with rheumatoid arthritis. In contrast with CIE the DD-RIE method is quantitative by reference to a standard curve based on an internal reference C3d preparation and its sensitivity and assay capacity are superior to CIE. All reagents and antibody preparation are commercially available and the production of standards is easy. No overlapping was observed between C3d values in plasma from healthy persons and patients with active classical rheumatoid arthritis. The DD-RIE is highly suitable for routine use in laboratories of clinical immunology.

The third complement factor (C3) and its in vivo cleavage products: interaction with lectins and precipitation with polyethylene glycol.

Five molecular forms of C3 expressing D but not C epitopes were identified following in vivo activation of the complement system. Examination of concanavalin A (Con-A) reactivity in crossed immunoelectrophoresis revealed that native C3, C3c and the beta mobile form 4 of C3d were completely precipitated by 100 micrograms Con A/cm2. The alpha-1 mobile form 1 of C3d did not interact with Con A, whereas the alpha-2 mobile forms 2 and 3 were retarded in electrophoretic migration by Con A. Native C3, C3c, and forms 4 and 5 of C3d were precipitated by 12% (w/v) polyethylene glycol (PEG). Form 1 of C3d was soluble in these PEG concentrations, whereas forms 2 and 3 were partially precipitated.

Influence of time, temperature and coagulation on the measurement of C3, C3 split products and C4.

Quantitative and qualitative immunoelectrophoretic analyses of circulating C3, C3 split products and C4 were performed in matched EDTA plasma and serum obtained from 5 normal subjects and stored for up to 48 h at room temperature (18 degrees C-22 degrees C) and 4 degrees C. Fluctuations in apparent levels of C3 were greater in serum than plasma stored at room temperature, a fall in levels seen by 24 h being followed by a significant increase. By contrast, levels of C3 did not alter if stored at 4 degrees C. C4 levels in both EDTA plasma and serum remained unchanged for 24 h, a slight decrease being seen at 48 h. Levels of C4 remained constant if samples were stored at 4 degrees C. Crossed immunoelectrophoresis revealed a significant progressive decrease in C3 levels and a simultaneous increase in C3c occurring after 4 h in serum and 8 h in EDTA plasma, stored at room temperature. In studies conducted at 4 degrees C, similar but delayed fluctuations were seen. A progressive and significant increase in C3d levels was seen in both plasma and serum samples stored at room temperature, levels rising to 276% (plasma) and 308% (serum) of levels seen at zero time. At 4 degrees C marginal increases in C3d levels only were observed. These results suggest that in vitro degradation of C3 and C4 are readily facilitated by temperature, time and coagulation, and that conditions of collection and storage of samples must be optimized for the accurate definition of activation of the complement cascade.

Complement activation reaches maximum during equilibrium between antigen and antibody in an in vitro model for thrombolysis with streptokinase.

Treatment with streptokinase (SK) of patients with acute myocardial infarction (AMI) is known to activate the complement system. In a previous investigation we found a great variation in the degree of complement activation taking place during infusion of SK in patients with AMI (range: 0-293% increase in pretreatment complement split product 3d (C3d) levels). In this in vitro study we added SK to serum with different concentrations of SK-antibodies (SK-Ab) and found that both the relative concentrations and the total concentrations of SK and Ab determined the degree of complement activation elicited by SK. This finding was in accordance with the Kendall-Heidelberger equation of antigen-antibody equivalence. Furthermore, we found parallel rises in C3d and C4d, indicating that complement was activated via the classical pathway. A condition for maximal complement activation is antigen-antibody equivalence.

Streptokinase, complement activation and hypotension.

The purpose of this study was to establish whether complement activation is the cause of transient hypotension during streptokinase infusion in patients with acute myocardial infarction. Thirteen patients with suspected acute myocardial infarction and treated with streptokinase were included. Complement 3d (C3d) as an indicator of complement activation was assessed in venous blood and blood pressure was measured. Ten patients had verified myocardial infarction. Three patients did not. Five patients developed an increase in C3d blood levels of more than 200% within 30 min. All patients developed a transient fall in blood pressure during infusion of streptokinase. This was related neither to presence of myocardial infarction nor to degree of complement activation. The mechanism of hypotension observed following the administration of streptokinase is not through complement activation, and thus how streptokinase induces hypotension is still obscure.