C-reactive protein: structural biology and host defense function

False increase in serum C-reactive protein caused by monoclonal IgM-lambda: a case report

Interference caused by human anti-animal antibodies has been described in many laboratory assays. Usually the antigen giving rise to these antibodies is not known. When present in sufficiently high titer, these antibodies may have a significant effect on laboratory assays, causing falsely increased or decreased values, to the detriment of patient care and laboratory diagnosis. We report a case of an 86-year old man who had greatly increased C-reactive protein (CRP) levels in serum (>500 mg/l), suggestive of an unusually strong inflammatory response such as seen in septicemia. Because this diagnosis was not consistent with his symptoms, CRP measurements were repeated using alternative methods, none of which gave CRP results higher than 12 mg/l. Protein electrophoresis followed by immunofixation showed a monoclonal IgM-lambda paraprotein (7 g/l), which bound the goat anti-CRP antibodies used in the first CRP assay. Precipitation of the IgM-lambda paraprotein eliminated the interference. Subsequent bone marrow tests did not reveal any blood malignancy, and the monoclonal IgM component was attributed to monoclonal gammopathy of unknown significance. In conclusion, an IgM-lambda paraprotein was shown to cause falsely elevated CRP values in an automated immunometric assay using goat anti-CRP antibodies.

Evolution of effectors and receptors of innate immunity

The bony fishes are derived from one of the earliest divergent vertebrate lineages to have both innate and acquired immune systems. They are considered by some to be an ideal model to study the underpinnings of immune systems precisely because of their phylogenetic position and the fact that their adaptive immune systems have not been elaborated to the extent seen in mammals. By the same token, examination of innate immune systems in invertebrates and early chordates can provide insight into how homologous systems operate in fish and higher vertebrates. Herein, we provide an overview of the molecular evidence that we hope helps clarify the evolutionary relationships of innate immune molecules identified in bony fishes. The innate immune systems being considered include select chemokines (CC and CXC chemokines and their receptors), cytokines (IL-1, IL-8, interferons, TGF-beta, TNF-alpha), acute phase proteins (SAA, SAP, CRP, alpha2M, and the complement components--C3-C9, MASP, MBL, Bf), NK cell receptors, and molecules upstream and downstream of the Toll signaling pathways.

Protective effect of C-reactive protein against the lethality induced by Vibrio vulnificus lipopolysaccharide

Vibrio vulnificus infection has attracted special interest because of its high mortality. A strong clinical association exists between hepatic dysfunction and increased morbidity and mortality from V. vulnificus infection. In this study, the effect of C-reactive protein (CRP), a typical hepatogenic acute phase protein, on the lethality induced by V. vulnificus lipopolysaccharide (LPS) was investigated in galactosamine-sensitized mice. The pretreatment of CRP, in a dose of at least 2 mg/kg, 2 hr before the challenge of LPS completely protected mice against the lethality by V. vulnificus LPS. The elevation of serum tumor necrosis factor-alpha (TNF-alpha) induced by LPS administration was not affected by CRP pretreatment. However, the LPS- or TNF-alpha-induced hepatotoxicity was completely prevented by CRP. These results indicate that CRP does not prevent the synthesis, but prevents the hepatotoxic action of TNF-alpha. The possibility that impaired production of acute phase proteins in patients with pre-existing hepatic dysfunction may predispose the higher risk of V. vulnificus infection needs to be evaluated further.

Serum amyloid A protein (SAA) in colorectal carcinoma

The changes in serum levels of serum amyloid A protein were studied in 67 patients suffering from colorectal carcinoma and compared to three other major acute phase proteins: C-reactive protein, alpha1-antichymotrypsin and alpha1-acid glycoprotein. Although the presence of colorectal carcinoma caused an increase in serum levels of all the acute phase reactants studied, serum amyloid A protein showed the most powerful reaction in pre-operative disease stage, with the mean value of 330 mg/l (range 7-2506 mg/l) as compared to the normal values of <1.2 mg/l obtained in 30 healthy adults. The mean serum amyloid A protein concentration increased to 487 mg/l after surgery, declining during the post-operative clinical course until the sixth chemotherapy cycle (from 167 mg/l to 64 mg/l), but never returned to the normal range. In the later chemotherapy cycles, mean serum amyloid A protein increased to 163 mg/l, probably as a result of the disease relapse. According to the statistical relations among exact confidence intervals for proportions, serum amyloid A protein showed the best specificity for colorectal carcinoma of all the acute phase proteins studied (83-100%) and also a sensitivity of 100%. We concluded that serum amyloid A protein seems to be a reliable parameter, which could be recommended for clinical routine as a non-specific tumour marker for colorectal carcinoma.

C-reactive protein and serum amyloid A protein in neonatal infections

In this study, we examine C-reactive protein (CRP) and serum amyloid protein A (SAA). Although the former is the best known and most commonly used indicator of inflammation, certain considerations underline the inadequacy of CRP determination alone for the early diagnosis of infection. In fact symptoms often precede the CRP elevation. SAA protein comprises a family of polymorphic apolipoproteins produced mainly by the liver, and several studies have stressed its importance in the diagnosis and monitoring of various diseases. Pathological SAA values are often detected in association with normal CRP concentrations. SAA rises earlier and more sharply than CRP. Finally, contrary to CRP, SAA presents the same trend in viral as well as bacterial infections. Although the data available on SAA in neonates are currently very limited, it is possible to postulate a role of primary importance for SAA in the management of neonatal infections.

High sensitivity C-reactive protein: biological variations and reference limits

Serum C-reactive protein (CRP) concentration was determined for 3605 subjects using an immunonephelometric assay improved to provide greater sensitivity. Subjects were from 5 to 75 years old and belonging to 1003 nuclear families recruited from the Stanislas Cohort Study between January 1994 and August 1995. Sample values for CRP ranged from 0.17 mg/l to 100 mg/l. Geometric means (mean - SD; mean +/- SD) were in the 5-14 years old group 0.37 (0.17-1.07) mg/l, in the 15-28 years old group 0.47 (0.17-1.38) mg/l and in the 29-75 years old group 0.98 (0.34-2.85) mg/l. For women, the geometric means were 0.38 (0.17-1.10) mg/l, 0.62 (0.20-1.90) mg/l and 0.98 mg/l (0.31-3.13) mg/l respectively. The interindividual variability ranged from 138% to 759% among different age classes. Biological factors associated with CRP concentration variations were examined and accounted for 25% of the CRP variability in men and 40% in women. The main biological factors statistically associated with CRP concentration variations in men were: drugs, leukocyte count, body mass index, tobacco consumption, age, and in women: drugs, leukocyte count, age, body mass index and hemoglobin concentration. These factors were used to define the exclusion and partition criteria when obtaining the reference samples. Medians for reference values ranged from 0.20 to 0.68 mg/l in males and from 0.20 to 0.78 mg/l in women.

Innate recognition systems in insect immunity and development: new approaches in Drosophila

Phagocytosis is important in immune defense and development in vertebrates and invertebrates. It leads to swift ingestion of microorganisms and dying cells by phagocytes. How particles are recognized is not well understood. Studies in insects, and Drosophila in particular, argue that these are powerful model systems to dissect this process.