The level of the serum opsonin, mannan-binding protein in HIV-1 antibody-positive patients.

The concentrations of mannan-binding protein (MBP) in consecutive samples from 10 HIV+ persons were estimated using an ELISA based on polyclonal rabbit anti-MBP. The changes in MBP with time were similar in HIV+ and HIV- persons, and did not appear to be of clinical significance. MBP was determined in a further 70 persons found HIV-1+ during a period of 2.5 years (1984-1986). Out of the total of 80 patients, 32 have by now died from AIDS. According to the serum level of MBP the HIV-infected persons were grouped into high (> 650 ng MBP/ml), intermediate (101-650 ng/ml), and low MBP (< 101 ng/ml). At the termination of the study the frequency of deaths/total in each of the groups were: high MBP, 14/39 (36%); intermediate MBP, 12/26 (46%); and low MBP, 6/14 (43%). There was no association between the MBP level of the individual and the progressive loss of CD4+ T cells, and the level of MBP was not predictive for the length of time between the detection of HIV antibodies and development of AIDS, nor for the duration of AIDS before death occurred. The number of HIV+ persons without detectable MBP (10%) was significantly higher than previously reported for healthy persons (2.4%, P = 0.027). The course of HIV infection does not seem to be influenced by the level of MBP, nor does the antimicrobial activity of MBP appear to affect the progression of AIDS. Further studies are required to substantiate the significance of absence of MBP in the susceptibility to HIV.     

Complement regulation in innate immunity and the acute-phase response: inhibition of mannan-binding lectin-initiated complement cytolysis by C-reactive protein (CRP)

Mannan-binding lectin (MBL) is an acute-phase protein which activates complement at the level of C4 and C2. We recently reported that the alternative pathway also is required for haemolysis via this ‘lectin pathway’ in human serum. CRP is another acute-phase reactant which activates the classical pathway, but CRP also inhibits the alternative pathway on surfaces to which it binds. Since serum levels of both proteins generally increase with inflammation and tissue necrosis, it was of interest to determine the effect of CRP on cytolysis via the lectin pathway. We report here that although CRP increases binding of C4 to MBL-sensitized erythrocytes, which in turn enhances lectin pathway haemolysis, it inhibits MBL-initiated cytolysis by its ability to inhibit the alternative pathway. This inhibition is characterized by increased binding of complement control protein H and decreased binding of C3 and C5 to the indicator cells, which in turn is attributable to the presence of CRP. Immunodepletion of H leads to greatly enhanced cytolysis via the lectin pathway, and this cytolysis is no longer inhibited by CRP. These results indicate that CRP regulates MBL-initiated cytolysis on surfaces to which both proteins bind by modulating alternative pathway recruitment through H, pointing to CRP as a complement regulatory protein, and suggesting a co-ordinated role for these proteins in complement activation in innate immunity and the acute-phase response.     

Effect of interleukin-2 on peripheral blood mononuclear cell cytokine production and the hepatic acute phase protein response

This study investigated the ability of recombinant interleukin-2 (IL-2) to modulate the ability of peripheral blood mononuclear cells (PBMCs) to stimulate an acute phase protein response in isolated human hepatocytes. The effect of IL-2 on the production of tumour necrosis factor-alpha (TNF) and interleukin-6 (IL-6) by PBMCs isolated from patients with gastrointestinal cancer, multiple organ failure, and healthy controls was also studied. The ability of supernatants from IL-2-treated PBMCs to elicit an acute phase response in hepatocytes was then investigated. IL-2 had no effect on IL-6 or TNF production by PBMCs isolated from any group in the presence or absence of bacterial lipopolysaccharide (LPS). Despite this, preincubation of PBMCs with IL-2 significantly reduced the potential of LPS-stimulated PBMC supernatants to stimulate production of alpha1 antichymotrypsin, alpha1-acid glycoprotein, and C-reactive protein by hepatocytes. These observations were not due to a direct effect of IL-2 on hepatocyte acute phase protein production. These findings suggest that in this model IL-2 may modulate PBMC-induced acute phase protein production through an IL-6 and TNF-independent pathway.     

The acute phase protein response in patients receiving subcutaneous IL-6.

IL-6, tumour necrosis factor-alpha (TNF-alpha) and IL-1 are thought to be the key mediators of the acute phase response although much of the evidence is based on in vitro studies. It is not clear to what extent each of the acute phase proteins are regulated in vivo by each of these cytokines. The aim of this study was to examine the effects of IL-6 treatment in eight patients with cancer on the concentrations of an extensive range of positive and negative acute phase proteins. It was part of a larger investigation to assess the value of IL-6 in the management of chemotherapy-induced thrombocytopenia. IL-6 was administered by a daily subcutaneous injection for 7 days at a dose level of 1, 3, or 10 micrograms/kg/day. Increases in the positive acute phase proteins, serum amyloid A, C-reactive protein, alpha 1-acid glycoprotein, alpha 1-antichymotrypsin, haptoglobin, alpha 1-antitrypsin, fibrinogen, complement component C3, and caeruloplasmin, were observed, with the greatest incremental changes and fastest responses being seen for C-reactive protein and serum amyloid A protein. The negative acute phase proteins transferrin, transthyretin and retinol binding protein all fell to a nadir within 48-96 h after the first IL-6 injection. Increases in complement component C4 were only found in two patients, which may be related to the increase in circulating TNF-alpha concentrations found only in these patients. This study has therefore shown that IL-6 is capable of causing changes in the majority of acute phase proteins in vivo. Although secondary induction of TNF-alpha was not observed in the majority of patients examined, it is still possible however that other cytokines involved in regulation of the acute phase response, such as IL-1, may have been induced and contributed to the overall response.     

C-reactive protein in acute viral infections

A sensitive solid-phase enzyme immunoassay procedure was used to determine the concentrations of C-reactive protein (CPR) in the acute and convalescent phase sera of patients with verified rubella, herpes simplex, cytomegalo, influenza A or B, enterovirus, or mycoplasma infection. In all infection groups about 90% (80% for influenza) elevated CRP values were observed in the acute phase sera (mean values in the different groups 16-57 micrograms/ml), the highest values exceeding or approaching 100 micrograms/ml. The serum CRP values were highest in all groups before the specific serum antibodies were detectable and decreased approaching the upper limit or normal controls (2 microgram/ml) within 2 weeks. Notable individual variation in the CRP production was seen. We conclude tha serum CRP determination should not be used as a reliable criterion to distinguish bacterial and viral infections.     

Structure of C-reactive protein excreted in urine during acute rejection episodes

During acute rejection of renal allografts C-reactive protein is excreted in urine in a monomeric form. We developed an immunochemical method for detecting monomeric C-reactive protein in human physiological fluids, which is based on latex agglutination.     

中国维吾尔族人群MBL基因启动子及第一外显子区SNP及其单倍型与基因型研究

收集新疆维吾尔族自治区维吾尔族一般人群血标本,提取白细胞基因组DNA,以序列特异性引物-多聚酶链反应技术检测其甘露聚糖结合凝集素(MBL)基因启动子区单核苷酸多态性位点-550G/C(称H/L等位基因)、-221C/G(X/Y)、+4C/T(P/Q)和结构基因第一外显子点突变CGT52TGT、GGC54GAC和GGA57GAA(分别称为D、B、C等位基因,野生型即A等位基因),并分析其单倍型与基因型。发现MBL基因启动子区等位基因主要为L、Y、P,第一外显子等位基因只发现B,未检出C和D;检出5种单倍型,其频率分别是HYPA 0.282、LYPA 0.268、LXPA 0.260、LYPB 0.120、LYQA 0.070。检出12种基因型,其频率分别为HYPA/HYPA 0.183、LXPA/LXPA 0.141、LYPA/LYQA 0.113、LYPA/LYPA 0.112、LYPA/LXPA 0.085、HYPA/LYPA 0.085、LXPA/LYPB 0.085、HYPA/LXPA 0.070、HYPA/LYPB 0.042、LYPA/LYPB 0.028、LYPB/LYQA 0.028、YPB/LYPB 0.028。     

Activation of the lectin complement pathway in post-streptococcal acute glomerulonephritis

The aim of the present study was to elucidate the correlation between complement pathways and clinicopathological findings in post-streptococcal acute glomerulonephritis (PSAGN). Immunohistological staining was performed on renal specimens obtained from 18 patients with PSAGN and 20 controls, using antibodies against IgG, IgA, IgM, C1q, C3c, C4, fibrinogen, factor B, C4-binding protein (C4-bp), C5b-9, CD59, mannose-binding lectin (MBL) and MBL-associated serine protease-1 (MASP-1). Controls showed no deposition of any antibody. In seven patients, glomerular deposits of C3c, C4, factor B, C4-bp, C5b-9, CD59, MBL and MASP-1 were found. In the remaining 11 patients, glomerular deposits of neither C4 nor MBL/MASP-1 were found, and glomerular deposits of C3c, factor B, C5b-9 and CD59 were evident. C4-bp was detected in seven of these 11 patients. Glomerular deposits of fibrinogen were detected in five of seven patients with MBL/MASP-1 deposits and in only two of 11 patients without MBL/MASP-1 deposits. Hematuria was prolonged in three of seven patients with MBL/MASP-1 deposits through follow up, whereas urinalysis was normal in all patients without MBL/MASP-1 deposits. However, the histological indicators were not different between the two groups. To the authors' knowledge this is the first report to show that complement activation through both the alternative and lectin pathways is evident in some patients with PSAGN. Complement activation is promoted in situ in the glomerulus.     

The significance of IgG subclasses and mannan-binding lectin (MBL) for susceptibility to infection in apparently healthy adults with IgA deficiency.

The aim of this study was to investigate the significance of IgG subclasses and MBL for susceptibility to infection in association with IgA deficiency. The study population consisted of 139 apparently healthy adult blood donors with IgA deficiency and normal serum levels of IgG and IgM, and an increased susceptibility to infection demonstrated at a population level. Additionally, 216 controls matched for age and sex were investigated. IgG4 deficiency was more common and the mean level of IgG4 lower in persons with IgA deficiency than in the controls. No significant associations could be demonstrated between overt IgG subclass deficiencies and increased susceptibility to infection. However, when the mean concentrations of IgG subclasses were analysed with regard to medical history, that of IgG1 was lower in persons who reported recurrent viral respiratory infections, that of IgG3 in persons who had episodes of severe infection in their history, and that of IgG4 in persons who had recurrent mild respiratory infections, compared with those who had no particular history of infections. In contrast, MBL deficiency-alone or combined with that of the IgG subclass-was not associated with increased susceptibility to infection in persons with IgA deficiency. The results indicate that the proneness to infections observed in a population of otherwise healthy persons with IgA deficiency can only for a small part be accounted for by concomitant deficiencies of IgG subclasses. Contrary to expectations, no synergism between the deficiencies of IgA and MBL could be demonstrated.     

The level of mannan-binding protein regulates the binding of complement-derived opsonins to mannan and zymosan at low serum concentrations

When sera diluted to 5% in a buffer containing calcium and magnesium were incubated with mannan-coated ELISA plates, C4 fragments, properdin and factor B were bound to the plates as well as the expected opsonic C3 fragments, C3b and C3bi. The calcium-dependent lectin mannan-binding protein, which is structurally similar to C1q, was also shown to bind in this assay and analysis of sera from 179 healthy blood donors revealed that the binding levels of all these proteins were highly significantly correlated. Results obtained with a previously described C3b opsonic assay using zymosan also correlated with the mannan-binding levels. When the sera were diluted to 5% in the presence of Mg-EGTA there was no detectable binding of complement proteins to the mannan surface, confirming that no alternative pathway activation occurred at this serum concentration. When sera were diluted to 5% in a buffer containing EDTA in order to study immunoglobulin binding in the absence of complement activation, the levels of bound IgG1, IgG2, IgG3, IgA and IgM antibodies were found to be completely unrelated to the C3bi binding levels previously observed. The results suggest that in this experimental system using low concentrations of serum, mannan-binding protein initiates an antibody-independent mechanism of cleavage of the classical pathway component C4, which subsequently regulates the degree of cleavage of C3 and recruitment of alternative pathway proteins.     

Urinary zinc excretion and acute phase response in cancer patients

We investigated urinary zinc and serum levels of C-reactive protein, alpha-1 acid glycoprotein, haptoglobin, transferrin and prealbumin in 55 patients with solid tumors and 20 controls. Urinary zinc, serum C-reactive protein, alpha-1 acid glycoprotein and haptoglobin were significantly higher, and serum prealbumin was significantly lower in cancer patients. A significant positive correlation between urinary zinc and C-reactive protein, alpha-1 acid glycoprotein and haptoglobin, as well as a negative correlation with transferrin and prealbumin were observed. Hyperzincuria in cancer patients appears to be linked to the acute phase response. Our data provide further evidence implicating systemic inflammatory response in increased urinary zinc excretion. Correspondence to: B. Melichar     

Influence of an established acute phase response on the severity of experimental nephritis.

Small doses of lipopolysaccharide (LPS) induced an acute phase response (APR), and a number of studies have also shown that this greatly enhances the severity of glomerular injury in the heterologous phase of nephrotoxic nephritis (hNTN), an experimental model of anti-glomerular basement membrane (GBM) disease. Here, we examined the influence of pre-existing subclinical infection and raised APR, assessed by plasma alpha 2-macroglobulin (alpha 2-M) concentration, on the degree of injury in this model of nephritis. Studies were initially performed to determine the normal range of alpha 2-M in rats and its modulation by IL-6 and different doses of LPS. Plasma concentration of alpha 2-M was found to be variable and dependent on the weight of the rats. Single injections of either LPS or IL-6 had a comparable effect, and continuous perfusions of LPS caused a progressive increase in alpha 2-M which peaked at 48 h and declined gradually over 1 week. Following induction of nephritis with 10 mg of anti-GBM antibody, rats with raised alpha 2-M had 14 +/- 3 mg/24 h albuminuria compared with 4 +/- 1 mg/24 h in rats with normal alpha 2-M (P < 0.001, Wilcoxon). Injection of 20 mg anti-GBM antibody caused 36 +/- 11 mg/24 h albuminuria compared with 16 +/- 4 mg/24 h (P < 0.001), respectively. However, all these rats remained active and none of them died. In contrast, injection of 0.25 microgram LPS before induction of nephritis with 10 mg anti-GBM antibody, in rats with raised alpha 2-M, caused severe albuminuria (115 +/- 23 mg/24 h) compared with rats having normal levels of alpha 2-M (72 +/- 15 mg/24 h, P < 0.05). Furthermore, rats with raised alpha 2-M also had severe systemic manifestations characterized by pulmonary haemorrhage and extensive glomerular thrombosis, and many of them died. These results demonstrate the potential effect of pre-existing subclinical infection and raised APR on severity of glomerular injury which may affect the outcome of experimental studies.     

A hypothesis resolving the apparently disparate activities of native and altered forms of human C-reactive protein

Although C-reactive protein (CRP) has been studied for over 60 years, the in vivo function of this acute-phase reactant has not been clearly defined. The literature on CRP has been divided here into three categories: the cyclic, pentameric blood-borne form of CRP termed ‘native’ CRP which has activities mainly associated with the resolution of inflammation, conformationally altered and aggregated forms of CRP which display pro-inflammatory properties, and proteolytic forms of CRP exhibiting mixed activities. Since the activities of certain forms of CRP in some cases contradict others, a hypothesis has been developed which reconciles these differences. It is proposed that distinct species of CRP are formed which have unique activities at an inflammatory site; conformationally altered and proteolytic forms of CRP are created in succession from bound native CRP at the inflammatory site due to local conditions (e.g. lowered pH, oxygen radicals, or possibly enzymes). Aggregated and/or conformationally altered forms of CRP initially promote inflammation, and subsequently produced peptide products either up or down regulate different leukocyte activities to aid in the progression of the inflammatory event. As the local conditions favoring the conversion of native CRP to altered forms begin to subside, native CRP then predominates at the site, facilitating the removal of cellular debris and resolution of the lesion.     

MPTP administration increases plasma levels of acute phase proteins in non-human primates (Macaca fascicularis)

Parkinson's disease (PD) is characterized by the loss of dopaminergic neurons in the Substantia Nigra pars compacta (SNpc). Parkinsonian patients and animal models of PD show inflammatory phenomena such as microglial activation and cytokine production that could modulate the progression of the disease, since they play a crucial role in the degenerative process. Since acute phase proteins (APPs) are involved in a number of homeostatic alterations and inflammatory processes, we analyzed the levels of APPs in primates before and after treatment with MPTP. A significant increase in C-reactive protein (CRP), serum amyloid A (SAA) and haptoglobin (HP) levels after MPTP treatment. These results demonstrate that MPTP induces a systemic generalized inflammatory reaction after specific dopaminergic neurotoxicity insult, suggesting that the inflammatory process in Parkinsonism may affect other immune-inflammatory responses outside the brain.     

The inhibitory effect of environmental ammonia on Danio rerio LPS induced acute phase response

Ammonia is a toxic by-product of amino acid catabolism and a common environmental pollutant that has been associated with increased disease susceptibility in fish although the mechanism is not well understood. We addressed the hypothesis that elevated environmental ammonia acts by impairing the acute phase response (APR). Specifically, we determined the impact of sub-lethal acute (24 h) and chronic (14 d) ammonia exposure on acute phase protein gene expression in zebrafish (Danio rerio) in response to a challenge with bacterial lipopolysaccharide (LPS: i.p. 10 μg/g after 24 h). A panel of LPS-responsive genes (SAA, HAMP, LECT2, Hp and IL1β) were identified and evaluated by real-time quantitative PCR. Ammonia was found to impair induction of SAA, HAMP and LECT2 by 50-90%. Both short (15 min, 1 h and 24 h) and long-term (14 days) exposure to high environmental ammonia concentrations significantly elevated whole-body cortisol levels compared with control fish. Our results reveal for the first time that exposure to high environmental levels of ammonia suppresses the innate immune response in fish. We hypothesize that high environmental ammonia-mediated elevation of cortisol levels in zebrafish may be playing a key role in this immunosuppression, while the mechanisms involved remains to be elucidated.     

An inhibitor of interleukin‐6 trans‐signalling,sgp130, contributes to impaired acute phase response in human chronic liver disease

In chronic liver disease, high circulating interleukin (IL)‐6 contrasts with a poor acute phase response. We evaluated the impact of liver and circulating IL‐6‐receptor (IL‐6R) forms on IL‐6 bioactivity in chronic liver disease. IL‐6, soluble IL‐6‐receptor and sgp130 levels were assayed in plasma from 45 patients with alcoholic liver disease, 84 with hepatitis C virus (HCV) infection undergoing transjugular liver biopsies and 15 healthy subjects. IL‐6R mRNA was quantified on liver extracts from 54 patients with alcoholic liver disease with or without cirrhosis and 18 HCV‐infected patients. The effect of gp130–Fc on fibrinogen secretion induced by IL‐6 trans‐signalling was evaluated on hepatocyte cultures. Levels of plasma IL‐6 and sgp130, but not soluble IL‐6R, increased with the stage of chronic liver disease, and correlated significantly with disease severity. Alcoholic liver disease patients had higher plasma IL‐6 levels than hepatitis C, but lower liver IL‐6R expression. In alcoholic and HCV‐related liver diseases, liver IL‐6R expression decreased with advanced fibrosis stage. In vitro, on hepatocytes, gp130–Fc blunted the acute phase response while soluble IL‐6R enhanced IL‐6 stimulation. In advanced chronic liver disease, high plasma IL‐6 is associated with low liver IL‐6R expression. This situation enables high plasma sgp130 to act as a major negative regulator of liver IL‐6 trans‐signalling, as demonstrated functionally here on hepatocytes. This might explain the poor acute phase response induced by IL‐6 in chronic liver disease.