A solid-phase enzyme immunoassay for C-reactive protein: clinical value and the effect of rheumatoid factor

Why C-reactive protein is one of the most requested tests in clinical laboratories?

C-reactive protein (CRP) is an acute-phase protein which is synthesized by the liver in response to the secretion of several inflammatory cytokines including interleukin 6 (IL-6), IL-1 and tumor necrosis factor (TNF). CRP was the first acute-phase protein to be described and adopted in clinical laboratories as an exquisitely sensitive systemic marker of inflammation and tissue damage. The measurement of CRP is widely used for the diagnosis and monitoring of inflammatory conditions, including sepsis, trauma, and malignancies. In the last decades, impressive advances in analytical methods (from qualitative to high-sensitivity assays), automation and availability of results in a short time, not only translated in an increasing demand for the right management of systemic inflammatory diseases, but also in evaluating subclinical inflammatory processes underlying atherothrombotic events. CRP measurement is one of the most requested laboratory tests for both the wide range of clinical conditions in which it may assure a valuable information and some analytical advantages due to the evidence that it is a "robust biomarker". Even recently, the measurement of CRP received new interest, particularly as a biomarker of severity of Coronavirus disease 2019 (COVID-19), and it deserves further concern for improving demand appropriateness and result interpretation.

A novel case of impaired C-reactive protein response following open-heart surgery: A case report and review of the literature

BACKGROUND

C-reactive protein (CRP) is expected to increase in response to a range of inflammatory stimuli such as infections or extensive tissue trauma.

CASE REPORT

We present a novel case of severely impaired CRP response following NSTEMI, influenza A infection and open-heart surgery in which serum CRP concentrations remained < 1 mg/L during an observational period of 28 days.

CONCLUSION

To our knowledge, no previous publications exists describing patients with a lack of CRP response following cardiothoracic surgery. We believe this to be a novel finding warranting further investigations regarding the etiology and prevalence of this phenomenon.

Association of Aquaporin-3, Aquaporin-7, NOS3 and CYBA polymorphisms with hypertensive disorders in women

Preeclampsia (PE), a pregnancy disorder influenced by oxidative stress and hypoxia, affects the health of the mother and baby and is associated with an increased risk of future hypertension (HT). Aquaporins are a family of water channels, comprising members that also transport glycerol (aquaglyceroporins) and hydrogen peroxide (peroxiporins), key molecules for metabolic homeostasis and redox signaling. Here, we investigated the association of Aquaporin-3 (AQP3; rs2231231), Aquaporin-7 (AQP7; rs2989924), NOS3 (4B/A intron) and CYBA (rs4673) genetic polymorphisms with the development of hypertensive disorders by qPCR/PCR in a cohort of 150 normotensive (NT) women (N = 90) or with previous PE (N = 60) during pregnancy. Prospectively, women were reclassified 2-16 years after pregnancy as NT (N = 98) or hypertensive (N = 48) and the genetic associations were reevaluated. In addition, genetic associations were reevaluated and compared between normotensive and hypertensive (HT) subjects. We found that AQP3 rs2231231, an aquaglyceroporin/peroxiporin, is associated with the development of HT, whereas AQP7, NOS3 and CYBA polymorphism did not correlate with PE or future HT. Because AQP3 was associated with hypertension only after pregnancy, its role might be related to later risk factors of hypertension such as metabolic syndrome or oxidative stress.

The effect of rheumatoid factor on three commercial immunoassays for serum cystatin C

Cystatin C (CysC) can be used to diagnose early changes in renal insufficiency. However, there are little researches to study whether there is an interference between the level of CysC and RF. Thus, we conducted this study to investigate it. We randomly selected 30 patients with high RF (RF concentration: 552.05 ± 476.23 IU/mL) and 33 healthy subjects with RF concentration <11.1 IU/mL and CysC were measured with different reagents and instruments; Interference experiment was also be included. The results showed that the measured CysC concentration increases with increasing RF concentration in a dose-dependent manner and CysC levels are falsely increased by RF interference depends on the reagents used (CysC reagent: Whitman, Nanjing, China). Reagent manufacturers should fully consider RF interference when developing CysC reagents, and evaluate them before they are sold. When selecting CysC reagents, we should evaluate RF interference to the measurement to avoid misleading results.

Regenerative potential of bone marrow mesenchymal stem cells on cadmium chloride-induced hepato-renal injury and testicular dysfunction in sprague dawley rats

The effect of bone marrow-derived mesenchymal stem cells on cadmium-induced liver and kidney damage was studied in Sprague Dawley rats. The study employed three animal groups: Group 1 served as control animals; Group 2 rats were dosed intra-peritoneally with 2 mg of cadmium chloride per kg body weight, and Group 3 rats were again dosed with a single intraperitoneal injection of 2 mg of cadmium chloride per kg body weight two doses of 10⁶ cells each intravenously. Finally, the animals were killed using halothane inhalation anesthesia. Semen analysis (total sperm count, viability, motility, and % of normal sperm), biochemical estimations (serum total protein, uric acid, creatinine, levels of enzymes ALT, AST, and ALP, and levels of hormones LH, FSH, Inhibin, and testosterone), and histopathological analysis of liver and kidney tissue sections (using hematoxylene and eosin stains) were conducted. The results showed that when compared to controls, cadmium exposure drastically decreased total sperm count, viability, motility, and % of normal sperm, decreased serum total protein, increased serum uric acid and creatinine levels, increased levels of ALT, AST, and ALP enzymes, decreased levels of testosterone and inhibin, increased levels of LH and FSH, and caused significant histopathological abnormalities in both kidney and liver tissues. Treatment with stem cells ameliorated the effects of cadmium-induced toxicity significantly (p < 0.05) of the histopathological and biochemical parameters. In conclusion, the study reinforces previous findings that bone marrow mesenchymal stem cells can ameliorate the toxic effects of cadmium chloride and may be used as a potential therapeutic strategy for cadmium-induced adverse effects.

In women with previous pregnancy hypertension, levels of cardiovascular risk biomarkers may be modulated by haptoglobin polymorphism

Preeclampsia (PE) may affect the risk for future cardiovascular disease. Haptoglobin (Hp), an acute phase protein with functional genetic polymorphism, synthesized in the hepatocyte and in many peripheral tissues secondary of oxidative stress of PE, may modulate that risk through the antioxidant, angiogenic, and anti-inflammatory differential effects of their genotypes. We performed a prospective study in 352 women aged 35 ± 5.48 years, which 165 had previous PE, 2 to 16 years ago. We studied demographic, anthropometric, and haemodynamic biomarkers such as C-reactive protein (CRP), myeloperoxidase (MPO), and nitric oxide metabolites (total and nitrites), and others associated with liver function (AST and ALT) and lipid profile (total LDL and cholesterol HDL, non-HDL, and apolipoproteins A and B). Finally, we study the influence of Hp genetic polymorphism on all these biomarkers and as a predisposing factor for PE and its remote cardiovascular disease prognosis. Previously preeclamptic women either hypertensive or normotensive presented significant differences in those risk biomarkers (MPO, nitrites, and ALT), whose variation may be modulated by Hp 1/2 functional genetic polymorphism. The history of PE may be relevant, in association with these biomarkers to the cardiovascular risk in premenopausal women.

Generation and characterization of a unique reagent that recognizes a panel of recombinant human monoclonal antibody therapeutics in the presence of endogenous human IgG

Pharmacokinetic (PK) and immunohistochemistry (IHC) assays are essential to the evaluation of the safety and efficacy of therapeutic monoclonal antibodies (mAb) during drug development. These methods require reagents with a high degree of specificity because low concentrations of therapeutic antibody need to be detected in samples containing high concentrations of endogenous human immunoglobulins. Current assay reagent generation practices are labor-intensive and time-consuming. Moreover, these practices are molecule-specific and so only support one assay for one program at a time. Here, we describe a strategy to generate a unique assay reagent, 10C4, that preferentially recognizes a panel of recombinant human mAbs over endogenous human immunoglobulins. This "panel-specific" feature enables the reagent to be used in PK and IHC assays for multiple structurally-related therapeutic mAbs. Characterization revealed that the 10C4 epitope is conformational, extensive and mainly composed of non-CDR residues. Most key contact residues were conserved among structurally-related therapeutic mAbs, but the combination of these residues exists at low prevalence in endogenous human immunoglobulins. Interestingly, an indirect contact residue on the heavy chain of the therapeutic appears to play a critical role in determining whether or not it can bind to 10C4, but has no affect on target binding. This may allow us to improve the binding of therapeutic mAbs to 10C4 for assay development in the future. Here, for the first time, we present a strategy to develop a panel-specific reagent that can expedite the development of multiple clinical assays for structurally-related therapeutic mAbs.

CRP detection from serum for chip-based point-of-care testing system

Most of point-of-care testing (POCT) to improve facilitates in diagnosis, treatment, and monitoring of patients. POCT technique has still remained a quantitatively and accurately detective effect. In this article, we demonstrated that real human C-reactive protein (CRP) in serum was detected for a chip-based point-of-care testing application based on a nanogap-embedded field effect transistor (FET), and the results were compared with those obtained via the enzyme-linked immunosorbent assay (ELISA) method. The limit of detection (LOD), determined from the standard curve, was 0.1 ng/ml, which is comparable to that of commercialized ELISAs. We evaluated that an improved detection range (0.1 ng/ml to 100 ng/ml) was achieved by comparing with commercialized ELISA. Control experiments to determine selectivity and to discern false-positive/false-negative rates were also performed. This report is the first description of the detection of CRP in human serum using a silicon-based biosensor.

Low grade inflammation, as evidenced by basal high sensitivity CRP, is not correlated to outcome measures in IVF

PURPOSE

To assess the relationship between low-grade inflammation, measured as basal high sensitivity (hs)-CRP, and IVF outcome.

METHODS

We recruited a total of 220 women undergoing infertility work up prior to IVF. Patients were selected for a BMI < 30 kg/m(2) with an upper age limit of 40 years. Serum hs-CRP levels were measured on day 3 of a spontaneous menstrual cycle preceding ovarian stimulation. A sensitive two-site ELISA was used for analysis. Dose of gonadotrophins required, follicles days 8 and 10, number of oocytes collected, number of oocytes fertilised and pregnancy outcome were recorded.

RESULTS

Median hs-CRP was 1.08 mg/L (0.43-3.00 mg/L). The hs-CRP was significantly related to BMI (r = 0.386, P < .001) but not to age and smoking habit. There were no significant relationships between basal hs-CRP and any of the measured IVF outcomes.

CONCLUSIONS

These findings demonstrate that serum hs-CRP concentration is not a predictive marker of cycle or pregnancy outcome in women undergoing IVF treatment.

Immunoassay on a power-free microchip with laminar flow-assisted dendritic amplification

We demonstrate a rapid (<30 min) and ultrasensitive (sub-picomolar) immunoassay on a microchip which needs no external power sources for fluid transport. We previously reported a rapid immunoassay of human C-reactive protein (CRP) on the power-free microchip with moderate sensitivity, i.e., a limit of detection (LOD) in sub-nanomolar range, due to the lack of signal amplification. In the current work, we have improved the LOD by 3 orders of magnitude by employing dendritic amplification (DA) methods. Specifically, a sandwich immunocomplex with a biotinylated secondary antibody was constructed on the inner surface of the microchannel as described in the previous report. Onto the immunocomplex, solutions of FITC-labeled streptavidin (F-SA) and biotinylated anti-streptavidin (B-anti-SA) were supplied to grow a dendritic structure. First, we alternately supplied the two solutions for layer-by-layer growth up to three layers. As a result, we obtained an LOD of 0.21 pM with a CRP sample volume of 1.0 microL and assay time of approximately 30 min under an ordinary fluorescence microscope. Second, to reduce the number of incubation steps, we have devised a new DA method: laminar flow-assisted dendritic amplification (LFDA). In this method, F-SA and B-anti-SA were simultaneously and continuously supplied from two laminar streams formed by a Y-shaped microchannel. The immunoassay with the LFDA for 10 min (total assay time of approximately 23 min) with a CRP sample volume of 0.5 microL yielded an LOD of 0.15 pM, which is equivalent to 75 zmol. The combination of the power-free microchip and the LFDA will provide a new opportunity for ultrasensitive point-of-care testing.

Change in pancreatic B-cell function (HOMA-B) varies in different populations with similar genetic backgrounds but different environments

OBJECTIVE

To determine whether pancreatic B-cell function varies in different populations with similar genetic backgrounds but different environments.

RESEARCH DESIGN/METHODS

We compared a specific migrant Gujarati community in the UK (n = 205) with people still resident in the same villages of origin in Gujarat, India (n = 246). Pancreatic B-cell function (HOMA-B) was determined and the influence of age, migration and other factors was explored.

RESULTS

As anticipated, there was an age-related decline in log(HOMA-B) in both groups. However, the age-related fall in log(HOMA-B) was more pronounced in the UK than in Gujarat (normalized beta-0.29 vs. -0.14, P for difference = 0.03). The decline of HOMA-B with age persisted after adjustment for body mass index (UK beta = -0.31; Gujarat beta = -0.16, P = 0.015, P < 0.001). There was no significant change in insulin sensitivity (HOMA-S) with age at either site, although insulin sensitivity was lower in the UK. Fasting non-estrified fatty acid (NEFA) levels rose with age in the UK but not in Gujarat (P = 0.003 for difference in gradients). In multiple linear regression analysis, lower log(HOMA-B) was independently associated with higher fasting log(NEFA) levels; normalized beta = -0.24, P < 0.001, age; beta = -0.16, P = 0.005, higher log(insulin-like growth factor binding protein-1); beta = -0.19, P = 0.007 and lower body mass index; beta = 0.26, P = 0.001. This model accounted for 25% of the variability in HOMA-B.

CONCLUSIONS

HOMA-B as a measure of B-cell function declines more rapidly with age in the migrant UK group than in Gujarat. This may be a direct consequence of chronically higher NEFA exposure in the UK group.

Arterial distensibility in adolescents: the influence of adiposity, the metabolic syndrome, and classic risk factors

BACKGROUND

Atherosclerosis develops from childhood, but the determinants of this preclinical stage remain uncertain. We examined the relations of classic coronary risk factors, adiposity and its associated metabolic disturbances, to arterial distensibility (a marker of early arterial disease) in 13- to 15-year-olds, some of whom had previously been studied at ages 9 to 11 years.

METHODS AND RESULTS

Brachial artery distensibility was measured by a noninvasive ultrasound technique in 471 British children in whom measures of adiposity, blood pressure, fasting blood lipids, and insulin had been made. All adiposity measures showed strong graded inverse relationships with distensibility. Inverse associations with distensibility were also observed for insulin resistance (homeostasis model assessment), diastolic pressure, C-reactive protein, and the number of metabolic syndrome components present, which had a graded relation to distensibility. Total and LDL cholesterol levels were also inversely related to distensibility, but less strongly than adiposity; homocysteine had no relation to distensibility. Although the relations of total and LDL cholesterol and diastolic pressure to distensibility had been present at 9 to 11 years of age, those of adiposity and insulin resistance were only apparent at 13 to 15 years.

CONCLUSIONS

Adiposity and its metabolic consequences are associated with adverse changes in the arterial wall by the teenage years. The graded relation with increasing adiposity was stronger than that for cholesterol and was seen at body mass index levels well below those considered to represent "obesity." This emphasizes the importance of population-based strategies to control adiposity and its metabolic consequences in the young.

Infliximab treatment reduces complement activation in patients with rheumatoid arthritis

BACKGROUND

Tumour necrosis factor (TNF) blocking agents decrease C reactive protein (CRP) levels in rheumatoid arthritis (RA). It has been shown that CRP may contribute to complement activation in RA.

OBJECTIVE

To assess the effect of intravenous infliximab treatment on complement activation, especially that mediated by CRP, in RA.

METHODS

35 patients with active RA (28 joint count Disease Activity Score (DAS28) >4.4) were treated with intravenous injections of infliximab (3 mg/kg, at weeks 0, 2, 6, 14, and 22). Clinical response and plasma levels of complement activation products, of CRP and of CRP-complement complexes, which are specific markers for CRP mediated complement activation, were assessed at the indicated time points up to 22 weeks. The relationship between CRP and CRP-complement complexes was analysed by paired t test between two time points and by generalised estimated equation, to test differences of variables over time.

RESULTS

At 2 weeks after the first dose, infliximab significantly reduced overall C3 and C4 activation and plasma levels of CRP and CRP-complement complexes were also significantly reduced at this time point. The effects of infliximab on CRP and complement continued throughout the observation period and were more pronounced in patients with a good response to infliximab treatment.

CONCLUSION

Treatment with infliximab decreases plasma levels of CRP and CRP dependent complement activation products and concomitantly may reduce complement activation in RA. Complement activation may be among the effector mechanisms of TNF in RA.

Progestogens of varying androgenicity and cardiovascular risk factors in postmenopausal women receiving oestrogen replacement therapy

OBJECTIVE

Medroxyprogesterone (MP) was used as the progestogen in randomized clinical trials of postmenopausal hormone replacement on cardiovascular risk. To attempt to understand the lack of benefit in these trials, we have examined the effects of MP and two other progestogens, the less androgenic desogestrel (DG) and the more androgenic norethisterone (NE), on cardiovascular risk factors against a background of oestrogen therapy.

DESIGN AND MEASUREMENTS

Thirty-four women were treated with conjugated equine oestrogens (CEE) 0.625 mg daily alone for 12 weeks, followed in random order by each of the three progestogens (DG 75 microg, MP 10 mg and NE 1 mg daily) given sequentially for three 12-week cycles while maintaining the same CEE treatment. We measured serum lipoproteins, paraoxonase activity, C-reactive protein (CRP), fibrinogen, fasting glucose and insulin levels at baseline, at the end of the oestrogen-only phase and at the end of each of the combined oestrogen and progestogen phases.

RESULTS

The addition of progestogens to CEE maintained the oestrogen-induced reduction in apolipoprotein B (apo B) and lipoprotein (a) [Lp(a)], and further lowered total cholesterol (P < 0.01) and fibrinogen (P < 0.001). CEE raised serum triglyceride (P < 0.001) and CRP (P < 0.01) concentrations, which reverted towards pre-oestrogen levels with progestogens. Progestogens significantly reduced high density lipoprotein (HDL) cholesterol (P < 0.05). NE was associated with the greatest reduction in HDL cholesterol and apo A1, but was most effective in preserving paraoxonase activity and reducing the potentially unfavourable oestrogen-induced increases in triglycerides and CRP.

CONCLUSION

Preconceptions that more androgenic progestogens necessarily have more unfavourable effects on cardiovascular risk factors may require revision.

Usefulness of elevated neopterin and C-reactive protein levels in predicting cardiovascular events in patients with non-Q-wave myocardial infarction

The value of monocyte/macrophage activity as a prognostic factor in patients with non-Q-wave myocardial infarction (NQMI) has not yet been investigated. Moreover, scarce data are available on the long-term predictive value of markers of inflammation in patients who experience a NQMI. The present study aimed to determine the predictive value of neopterin, alone and in relation to levels of C-reactive protein, on the recurrence of major clinical cardiovascular events in patients who had a NQMI.

C-reactive protein and the insulin-like growth factor (IGF)-system in relation to risk of cardiovascular disease in different ethnic groups

Inflammatory processes, marked in part by the acute phase reactant C-reactive protein (CRP) and insulin resistance are implicated in atherogenesis. Low insulin-like growth factor-I (IGF-I) and IGF binding protein-1 (IGFBP-1) concentrations are closely associated with insulin resistance. We examined CRP in ethnic groups with differing risk for cardiovascular disease and type 2 diabetes and its relationship with insulin sensitivity (Homeostasis model assessment (HOMA)-S) and the IGF system. European (n=155), Pakistani (n=108) and African-Caribbean (African Caribbean) (n=177) origin participants were randomly sampled from population registers. All underwent basic anthropometry, glucose tolerance testing and measurement of insulin sensitivity, CRP and other metabolic variables. CRP was significantly lower in African Caribbean men and women than in other ethnic groups. Across all groups CRP correlated negatively with (HOMA-S) (rho=-0.29, P<0.001). Regression analysis which included ethnicity and body mass index (BMI) showed that low HOMA-S (beta=-0.17, P<0.001) and low IGFBP-1 (beta=-0.14, P<0.001) were independently and inversely associated with CRP, but the effect was modified by obesity. In obese subjects insulin sensitivity was not associated with CRP. However, for the whole population, a 2.7 mg/l increase in CRP was associated with a 50% (95% confidence interval (CI) 10-210%) greater risk of WHO defined metabolic syndrome, independent of IGF-I (odds ratio (OR) 0.46 (95% CI 0.22-0.96)), IGFBP-1 (OR 0.58 (0.44-0.76)), female sex (OR 0.43 (0.22-0.84)), NEFA (OR 1.06 (1.03-1.09)) and Pakistani ethnicity. High CRP (as a measure of chronic subclinical inflammation), low IGF-I and low IGFBP-1 are independently associated with the presence of the metabolic syndrome and with insulin resistance. In obese subjects insulin sensitivity is not associated with changes in CRP whilst in non-obese subjects CRP independently contributes to variation in HOMA-S.

Relation of C-reactive protein to body fat distribution and features of the metabolic syndrome in Europeans and South Asians

OBJECTIVE

To investigate the association between circulating C-reactive protein (CRP) concentrations and indices of body fat distribution and the insulin resistance syndrome in South Asians and Europeans.

DESIGN

: Cross-sectional study.

SUBJECTS

A total of 113 healthy South Asian and European men and women in West London (age 40-55 y, body mass index (BMI) 17-34 kg/m(2)).

MEASUREMENTS

Fatness and fat distribution parameters (by anthropometry, dual-energy X-ray absorptiometry and abdominal CT scan); oral glucose tolerance test with insulin response; modified fat tolerance test; and CRP concentration by sensitive ELISA.

RESULTS

Median CRP level in South Asian women was nearly double that in European women (1.35 vs 0.70 mg/1, P=0.05). Measures of obesity and CRP concentration were significantly associated in both ethnic groups. The correlation to CRP was especially strong among South Asians (P<0.01) for measures of central obesity (waist girth and visceral fat area), whereas BMI and percentage fat were more significantly associated with CRP in Europeans (P<0.05). In South Asians the associations of CRP with visceral fat area and waist girth persisted after adjustment for either BMI or percent fat (all, P<0.05). In age-, sex- and smoking-adjusted regression analyses CRP concentrations were significantly associated with fasting and 2 h insulin and lipid levels in both ethnic groups (P<0.05). When further statistical adjustment was made for visceral fat area these associations were abolished (P>0.15).

CONCLUSION

We suggest that adiposity and in particular visceral adipose tissue is a key promoter of low-grade chronic inflammation. This observation may in part account for the association of CRP with markers of the metabolic syndrome. Future studies should confirm whether CRP concentrations are elevated in South Asians and whether losing weight by exercise or diet, or reduction in visceral fat mass, is associated with reduction in plasma CRP concentrations.

Occurrence of C-reactive protein in cryoglobulins

A previous case report described the formation of a complex between a monoclonal IgA with cryolabile properties and C-reactive protein (CRP). Our study provides the first evidence for the frequent occurrence of CRP in cryoglobulins (Cg) of all three types according to Brouet's classification. We performed a systematic immunochemical analysis of cryoglobulins from 18 patients by Western blotting and in 15 of 18 cryoprecipitates a single band (23 KD), immunoreactive with anti-CRP antibody, was demonstrable irrespective of the clonal composition of the cryoglobulins. This band was detectable in 4/5 of type I, in 6/8 of type II, and in 5/5 of type III cryoprecipitates, classified according to Brouet et al. In addition, the complement proteins C1q and C3 were present in nearly all CRP-containing cryoglobulins, presumably reflecting previous activation of the classical complement pathway at least. All three CRP-negative cryoprecipitates were derived from sera with low cryoglobulin content (1-2 g/l). Longitudinal investigation of 23 cryoprecipitates from seven patients confirmed that successful detection of CRP by Western blotting depends on the protein concentration of the cryoglobulins. Since complexed CRP was previously shown to be an effective activator of complement, via C1q binding, CRP may modulate pathophysiologic effects mediated by cryoglobulins in vivo.

Associations of C-reactive protein with measures of obesity, insulin resistance, and subclinical atherosclerosis in healthy, middle-aged women

Obesity, the insulin resistance syndrome, and atherosclerosis are closely linked and may all be determinants of an increased acute-phase response. In this study, we examined the relationship of C-reactive protein (CRP) with measures of obesity, variables of the insulin resistance syndrome, and intima-media thickness of the common carotid arteries in 186 healthy, middle-aged women selected from the general population. Associations were assessed by regression analysis. CRP was strongly associated with body mass index (BMI) and waist circumference. CRP was also associated with other variables of the insulin resistance syndrome, including blood pressure, insulin, high density lipoprotein cholesterol, triglycerides, apolipoprotein A1 (inversely), plasminogen activator inhibitor-1 antigen, and tissue-type plasminogen activator antigen. Associations between CRP and the variables of the insulin resistance syndrome disappeared after controlling for BMI but remained significant for plasminogen activator inhibitor-1 antigen only. The association of CRP with common carotid artery intima-media thickness was weak and limited to ever-smokers. BMI explained 29.7% of the variance of CRP, whereas common carotid artery intima-media thickness explained only 3.7%. The results of this population-based study indicate that adiposity is strongly associated with CRP in healthy, middle-aged women. In this population, BMI accounted for the relationship between CRP and other variables of the insulin resistance syndrome. Further studies should determine whether losing weight ameliorates the inflammatory state.

Plasma cytokine levels and coagulation and complement activation during use of the extracorporeal liver assist device in acute liver failure

Multiple organ failure frequently occurs in patients with acute liver failure, and this has been associated with increased cytokine production. Treatment by hemoperfusion with an extracorporeal liver assist device (ELAD) containing human liver-derived cells was performed in 12 patients with acute liver failure. Over the first 6 h, there were significant increases in plasma tumor necrosis factor alpha (TNFalpha; from 114+/-54 pg/ml [mean+/-SEM] to 236+/-161 pg/ml, p < 0.05) and interleukin (IL)-6 (260+/-121 pg/ml to 445+/-149 pg/ml, p < 0.05) but not in interferon gamma (IFNgamma). A similar pattern with a small peak increase was observed for complement C5b-9 complex. Plasma C-reactive protein (CRP) and thrombin antithrombin (TAT) III complex showed small peaks after 24 h of ELAD hemoperfusion. No such changes were seen in 12 control patients with acute liver failure who were treated with intensive care alone. These transitory effects, without changes in blood pressure, are likely to be due to the contact of the blood with the dialyzer membrane. There was no evidence of the clearance of cytokines by the ELAD.

Pro-inflammatory cytokine release and mediation of the acute phase protein response in fulminant hepatic failure

OBJECTIVE

To study the relationship between interleukin-6 (IL-6), tumour necrosis factor (TNF) and the acute phase protein C-reactive protein (CRP) in patients with fulminant hepatic failure (FHF) and to investigate the potential of peripheral blood mononuclear cells (PBMC) isolated from these patients to stimulate CRP production by isolated human hepatocytes in vitro.

SETTING

Patients with FHF were studied at the time of their admission to the intensive care unit.

STUDY DESIGN

Serum TNF and IL-6 were measured in 12 patients with FHF, PBMC from 6 of these patients were then cultured in the presence and absence of lipopolysaccharides (LPS). TNF and IL-6 in serum and supernatants were measured by ELISA. PBMC supernatants were added to isolated human hepatocytes and CRP production was measured.

RESULTS

Serum IL-6 (348 +/- 172 pg/ml) and TNF (118.5 +/- 15.5 pg/ml) were elevated compared with healthy controls (not detected) and these observations were matched by elevated serum CRP in patients with FHF (38.9 +/- 7 mg/l). Both the production of IL-6 and TNF by PBMC isolated from patients with FHF and the potential of supernatants from these cells to stimulate CRP production by hepatocytes in vitro was significantly reduced compared with controls.

CONCLUSION

Despite the observation that patients with FHF have an elevated hepatic acute phase response, PBMC from patients with FHF have reduced potential to produce IL-6 and TNF and elicit an acute phase response in vitro by the time of patient admission to the intensive care unit. One explanation for this observation is early activation and exhaustion of PBMC in vivo.

Enzyme-linked immunosorbent assay using F(ab')2 fragment for the detection of human pulmonary surfactant protein D in sera

We developed an enzyme-linked immunosorbent assay (ELISA) for detection of SP-D in serum using recombinant SP-D as a standard and horseradish peroxidase conjugated F(ab')2 fragment of mouse monoclonal antibody IgG to avoid the interaction of serum factors including rheumatoid factor. The use of F(ab')2 fragment dramatically decreased the value of serum SP-D concentration in rheumatoid arthritis patients without pulmonary complication to the close level of healthy volunteer. In contrast, the patients with collagen disease having interstitial pulmonary pneumonia exhibited consistently elevated levels of serum SP-D. The use of new ELISA with recombinant SP-D and F(ab')2 fragment of anti-SP-D monoclonal antibody gives a greater advantage for the accurate detection of SP-D in sera from patients with idiopathic pulmonary fibrosis, interstitial pneumonia with collagen disease and pulmonary alveolar proteinosis without interference of rheumatoid factor.

Soluble interleukin-6 receptor strongly increases the production of acute-phase protein by hepatoma cells but exerts minimal changes on human primary hepatocytes

Interleukin-6 (IL-6) interacts with a system of receptors, which include a 80-kDa IL-6-binding subunit (IL-6R) and a transducing element (gp130). The soluble form of IL-6R (sIL-6R) can bind its ligand and induce cellular responses by association with gp130, thus acting as an IL-6 agonist. We and others have previously shown that the responsiveness to IL-6 is different in hepatoma and human primary hepatocytes. We therefore compared the effects of sIL-6R on the two types of cells, and on the B9 hybridoma, another IL-6-sensitive cell line. Human primary hepatocytes, hepatoma cells PLC/PRF/5, and B9 cells were incubated with different concentrations of IL-6, sIL-6-R, or both. The hepatocyte culture supernatants were tested for their content of acute-phase proteins (APP). The proliferation of B9 cells was assessed by a colorimetric method. Results showed that sIL-6R alone markedly increased the production of APP by hepatoma cells in a dose-dependent manner, but affects only minimally primary hepatocytes and the proliferation of B9 cells. The combinations of IL-6R and its ligand enhanced the effects of Il-6 alone in both PLC/PRF/5 and B9 cells, but had no effect on primary hepatocytes. An immunohistochemical study indicated that the cell-surface expression of IL-6R was dramatically lower in hepatoma cells than in primary hepatocytes. In conclusion, our results show that the expression of IL-6R is low in the hepatoma cell PLC/PRF/5 when compared with primary hepatocytes and that this difference can, at least partly, explain their deficient responsiveness to IL-6. On the other hand, it appears that IL-6R expression by primary hepatocytes is sufficient and that circulating sIL-6R is unlikely to play a significant role in the modulation of IL6 effects.

IL-1 receptor antagonist (IL-1Ra) does not inhibit the production of C-reactive protein or serum amyloid A protein by human primary hepatocytes. Differential regulation in normal and tumour cells

The synthesis of some class 1 acute-phase proteins (APP), including C-reactive protein (CRP) and serum amyloid A (SAA) protein is completely blocked by the IL-1 receptor antagonist (IL-1Ra), whereas the production of fibrinogen, a class 2 APP, is increased by IL-1Ra in hepatoma cells, but this has never been tested in human hepatocytes in primary culture. Since previous studies on the contributions of cytokine inhibitors in connective tissues diseases suggested that IL-1 and tumour necrosis factor-alpha (TNF-alpha) might play an important role in the regulation of CRP, we decided to examine in more detail the respective roles of IL-1 beta, IL-6, and TNF-alpha and their inhibitors in the production of APP by human primary hepatocytes versus the hepatoma cell line PLC/PRF/5. In the hepatoma cell line, IL-1 beta and/or TNF-alpha had synergistic effects with IL-6 on the production of CRP and SAA. In contrast, these cytokines were devoid of effect in normal hepatocytes. The production of fibrinogen was increased by IL-6 and decreased by IL-1 (and TNF-alpha) in both cell types. The secretion of CRP and SAA by primary hepatocytes incubated with a cytokine-rich mononuclear cell-conditioned medium was totally unaffected by IL-1Ra or anti-TNF-alpha antibodies. In contrast, the addition of IL-1Ra increased the production of fibrinogen by both hepatoma cells and primary hepatocytes incubated with the mononuclear cell-conditioned medium. We therefore conclude that IL-1 beta and TNF-alpha do not exert any significant effect on the synthesis of CRP and SAA by human primary hepatocytes.

Serum haptoglobin and C-reactive protein in human skeletal fluorosis

Circulating levels of haptoglobin and C-reactive protein were studied in patients of skeletal fluorosis and compared with two types of controls. The first type of control included normal healthy individuals consuming water containing permissible levels of fluoride (up to 1 mg/L). The second type of control included individuals consuming water contaminated with fluoride (1.2-14.5 mg/L) but not exhibiting clinical manifestations of skeletal fluorosis. A significant increase in the levels of haptoglobin (p < 0.01) and C-reactive protein (p < 0.01) as well as a raised erythrocyte sedimentation rate were seen in patients of skeletal fluorosis as compared to both types of controls. The present study suggests the possibility of a subclinical inflammatory reaction occurring in patients with skeletal fluorosis.

Acute phase proteins in the monitoring of inflammatory disorders

The acute phase reaction is in most circumstances a good indicator of (local) inflammatory activity and tissue damage. CRP is a direct and quantitative measure for the acute phase reaction and due to its fast kinetics provides adequate information of the actual situation. The ESR on the contrary is in fact an indirect measure of the acute phase reaction. It does react much slower to changes of inflammatory activity and is influenced by a number of other factors. From studies on the 'behaviour' of CRP it has become clear that diseases may differ with regard to the extent in which they induce an acute phase response. Incidental measurement of the CRP level may add to the diagnostic procedure in selected cases, e.g. in the differentiation between a bacterial and a viral infection or between a bacterial infection and an exacerbation of diseases like SLE. In case of an extremely elevated CRP level (> 100 mg/litre) the possibility of a bacterial infection should always be considered. In clinical practice CRP is particularly useful when serial measurements are performed. The course of the CRP level may be useful for the monitoring of the effect of treatment and for the early detection of postoperative complications or intercurrent infections. The relationship between CRP and the local production and effects of cytokines on the one hand, and the possible functional role of CRP in the inflammatory process on the other hand have surely added a dimension to the clinical use of CRP as a parameter of inflammatory activity.

Value of serum C-reactive protein concentrations in febrile children without apparent focus

We examined the value of serum C-reactive protein (CRP) in febrile children without an apparent focus of infection, (i) as a tool to differentiate bacteraemia and bacterial infection from a non-bacterial illness (NBI), and (ii) as an indicator of recovery or complications. Included in the study were 100 children up to the age of 3 years with a temperature of > or = 38.5 degrees C, without an apparent focus. The serum CRP concentration was measured on days 1, 3 and 5 of evaluation and correlated with the final diagnosis and outcome. The serum CRP was 40 mg/l and above in 95% of patients (18/19) with bacteraemia and also in seven of the eight with purulent meningitis, while it was < 40 mg/l in 84% of patients (52/62) with NBI (mean (SD) 22 (28.6) mg/l). The mean serum CRP concentration among six children with a culture-positive urinary tract infection (16.3 (8.3) mg/l) and five with otitis media (9 (5.7) mg/l) was similar to those with NBI. The sensitivity of serum CRP > or = 40 mg/l for diagnosis of bacteraemia was 95% and the positive predictive value 67%. On serial monitoring, a fall in the CRP concentration was a sensitive indicator of recovery from infection and provided the earliest clue to therapeutic response long before a fall in temperature.

Measurement of plasma concentrations of polymorphonuclear elastase-alpha 1 proteinase inhibitor (elastase-alpha 1 antitrypsin) in patients with rheumatoid arthritis: interference by rheumatoid factor

The plasma concentration of granulocyte elastase in complex with alpha 1 proteinase inhibitor was determined in 32 patients with rheumatoid arthritis and eight with seronegative spondarthritis complicated by peripheral joint synovitis. Most patients had concentrations of complex which were within the range of the control group when measured by an 'in-house' enzyme linked immunosorbent assay, though several of the patients with rheumatoid arthritis had raised concentrations. When the complexes were measured by a commercially available assay, however, much higher values were obtained for many of the patients with rheumatoid arthritis. Evidence is presented indicating that the commercially available assay may suffer seriously from interference by rheumatoid factor. The possibility is discussed that most patients with rheumatoid arthritis may have plasma concentrations of elastase-alpha 1 PI which are normal or only slightly raised, and that previously published reports using assay systems similar to that available commercially might also have produced falsely raised values for many individuals with rheumatoid arthritis.

Rapid determination of C-reactive protein by enzyme immunoassay using two monoclonal antibodies

Several monoclonal antibodies for human C-reactive protein (CRP) were characterized, and two antibodies binding to separate domains were used to construct a rapid and simple immunoenzymometric assay for CRP. The assay consists of a single 15 min immunological reaction during which CRP forms a complex with a peroxidase-labelled antibody and with another antibody attached to the test-tube wall. The immobilized complex is detected by a 3 min colour reaction using peroxidase substrate. The quantitative measuring range of the assay is 0.04-5 mg/l, and no hook occurs at five-fold higher values. The sensitivity of the method allows reliable determination of low CRP levels, eg. in paediatric samples. The values obtained with the present assay correlated well with turbidimetric results.

von Willebrand factor is an acute phase reactant in man

Plasma von Willebrand factor antigen (vWfAg) concentrations in 19 patients with acute infectious illnesses of bacterial, viral or parasitic origin were significantly elevated with a mean greater than 3-fold above normal. In individual patients the elevation of vWf correlated strongly with the elevation of serum C-reactive protein (CRP). When patients were studied longitudinally, vWfAg and CRP concentrations both returned to normal values over 3-4 weeks. Similarly, in 14 volunteers infected with cold virus, vWfAg and CRP levels rose significantly and fell together during the course of infection. VWf is thus an acute phase reactant in man.

Selection and performance of monoclonal anti-C-reactive protein in ELISA quantitative assay

Nine monoclonal anti C-reactive protein (CRP) antibodies were tested as peroxidase-conjugates in a CRP binding to a solid-phase phosphorylethanolamine (PE) assay. One monoclonal antibody was selected due to its high yield of conjugate, titre and stability. The use of monoclonal antibodies increased assay sensitivity, precision and allowed assay simplification by the simultaneous rather than sequential incubation of CRP and conjugate. Comparison with nephelometry and CRP binding to PE assay using polyclonals gave correlations greater than or equal to 0.9. By using monoclonal conjugates to assay human sera, healthy adult CRP levels were found to be lower than by using polyclonal conjugates. Samples with very low CRP contents might now be assayed with higher precision.

Lactoferrin and C-reactive protein in response to cytostatic drugs with emphasis on methotrexate

In this study plasma concentrations of lactoferrin (LF) and C-reactive protein (CRP) are examined in 9 children with different kinds of cancer but without any intercurrent infections. New, sensitive enzyme-linked immunosorbent assay for LF and CRP are described. The samples are drawn before, during, and after the cytotoxic drugs are given. The cytotoxic courses include cis-platinum, vincristine, adriamycin, cytarabine, and methotrexate (6 g/m2/24 h and 33.6 g/m2/24 h). During the infusion of methotrexate 33.6 g/m2 the concentrations of LF are increased, only a small increase of CRP is observed, and for the other groups there is no changes of both parameters.

Use of whole Streptococcus pneumoniae cells as a solid phase sorbent for C-reactive protein measurement by ELISA

Monolayers of pneumococcus (serotype 27) on flat bottom polystyrene microtiter plates were used as a solid phase sorbent for the determination of C-reactive protein (CRP) by ELISA. After binding to the monolayer, CRP was quantified with peroxidase conjugated rabbit anti-human CRP immunoglobulin. The method is sensitive (5 micrograms/ml), rapid (less than 2 h) and correlates well with a laser nephelometric assay (r = 0.95, P less than 0.001), and with a classical sandwich ELISA (r = 0.95, P less than 0.001).

Interference of IgM rheumatoid factor with nephelometric C-reactive protein determinations

Different nephelometric assay systems for quantitation of C-reactive protein (CRP) were compared with radial immunodiffusion (RID) and tested for their susceptibility to interference by serum IgM rheumatoid factor (RF). In 3 nephelometric assays, RF was found to elevate CRP values. Sera with high RF content from patients with rheumatoid arthritis gave significantly higher CRP values by nephelometric assay than by RID; the addition of purified RF to RF-negative sera increased CRP values markedly; and removal of RF from sera corrected falsely elevated CRP values. This interference by RF is explained by the action of human RF as a (secondary) antibody reacting with complexed mammalian IgG anti-human CRP in the assay. In this way the nephelometric signal is enhanced to give falsely elevated CRP values. In contrast, the gel diffusion RID method does not suffer from this non-specific interference.