Primary structure of human C-reactive protein

C-reactive protein - My perspective on its first half century, 1930-1982

C-reactive protein (CRP) was discovered in 1930 in the sera of patients during the acute phase of pneumococcal pneumonia and was so named because it bound to the C-polysaccharide of the pneumococcal cell wall. During the next half century many questions raised by this discovery were answered. Phosphorylcholine was found to be the moiety of the C-polysaccharide to which CRP bound. The molecular structure of CRP was elucidated: five identical subunits arranged in cyclic symmetry, giving rise to the term pentraxin. Initially felt to be not normally present in the blood, CRP was found to be a component of normal serum in trace amounts. Its site of origin was determined to be the hepatocyte. It became clear that the presumed humoral mediator responsible for CRP induction was of leukocytic origin. Binding of CRP to its ligand activated the complement system, one of the important effector mechanisms of innate immunity. CRP was found to stimulate phagocytosis of some bacterial species via binding to Fc receptors and was found to be protective in vivo against the pneumococcus in mice. It appeared likely that a related function of CRP was clearance of necrotic tissue. CRP was recognized as being a highly evolutionary conserved molecule. Its discovery during the acute phase of pneumococcal pneumonia led to its being dubbed an acute phase protein. What we today call "the acute phase response", refers to the large number of behavioral, physiologic, biochemical, and nutritional changes that occur during inflammatory states.

Optimization of the secretory expression of recombinant human C-reactive protein in Pichia pastoris

Human C-reactive protein (CRP), a classical human acute-phase plasma protein, is not only a sensitive systemic inflammatory marker but also an independent risk predictor of cardiovascular diseases. However, existing heterologous expression systems for expressing CRP is not efficient and cost-effective for large-scale industrial production of CRP to meet the growing market demand for CRP. This study aims to improve the secretion of recombinant CRP by Pichia pastoris via optimizing signal peptides, promoters and carbon sources. The CRP genes with encoding four different signal peptides were designed and synthesized. The genes were cloned into pPICZαA or pPICZ B, respectively via splicing by overlap extension polymerase chain reaction (SOE-PCR) technology and expressed in P. pastoris X-33, regulated by the alcohol oxidase I promoter (pAOX1). The CRP led by the α-mating factor secretion signal peptide (α-MF) was secreted at the highest level in these signal peptides. Then, a constitutive construct and expression of the CRP genes were achieved by switching to the glyceraldehyde-3-phosphate dehydrogenase promoter (pGAP). Subsequently, different carbon sources and at different concentrations were used to further improve the secretion of CRP. The expression of CRP with the α-MF driven by the pGAP gave the highest yield of secreted CRP, about 3 mg/l of culture on the optimized culture conditions. The purified recombinant CRP exhibited good immunoreactivity determined by ELISA with anti-human CRP monoclonal antibody. The efficient engineering strategy established in this work might provide potential uses in large-scale industrial production of human CRP in the future.

Is serum CRP level a reliable inflammatory marker in pediatric nephrotic syndrome?

BACKGROUND

This study tested the hypothesis that during massive proteinuria, C-reactive protein (CRP) may be lost into the urine along with other proteins, making serum CRP (sCRP) level an unreliable marker of infection severity in nephrotic syndrome (NS).

METHODS

Children with active NS (n = 23) were compared with two matched control groups: patients with febrile non-renal infectious disease (n = 30) and healthy subjects (n = 16). Laboratory measurements included sCRP, urine protein, creatinine, IgG, and protein electrophoresis. Urinary CRP (uCRP) was measured by ELISA.

RESULTS

Sixty-nine patients were enrolled: 23 patients with NS, 30 patients with non-renal febrile infectious diseases, and 16 healthy children. Median uCRP concentrations were 0 mcg/gCr (0-189.7) in NS, 11 mcg/gCr (0-286) in the febrile group, and 0 mcg/gCr (0-1.8) in the healthy group. The uCRP/creatinine ratio was similar in the NS and healthy groups (p > 0.1) and significantly higher in the febrile group than the other two groups (p < 0.0001). There was no association of uCRP concentration with severity of proteinuria or IgG excretion.

CONCLUSIONS

NS in children is not characterized by significant loss of CRP into the urine. Therefore, sCRP may serve as a reliable marker of inflammation in this setting. The significant urinary excretion of CRP in children with transient non-renal infectious disease might be attributable to CRP synthesis in renal epithelial cells.

Serum hsCRP: A Novel Marker for Prediction of Cerebrovascular Accidents (Stroke)

INTRODUCTION AND OBJECTIVES

Strokes are caused by disruption of the blood supply to the brain. This may result from either blockage or rupture of a blood vessel. Yearly 15 million people worldwide suffer a stroke. India ranks second worldwide in terms of deaths from stroke. The incidence of stroke increases with age affecting the economically productive middle aged population. Hypertension and male sex are other risk factors for stroke. C-Reactive Protein (CRP) is an acute phase protein whose concentration rises in blood following inflammation. Formerly, assays for CRP detected its rise only after significant inflammation. However, recently developed high sensitivity assays (hsCRP) enable the measurement of CRP in individuals who are apparently healthy. Several studies indicate that hsCRP is elevated in individuals who are at risk of developing Coronary Artery Disease or Cerebrovascular events, the elevation may be found years before the first detection of vascular problems. In the absence of other biochemical markers, the present study aimed to evaluate the predictive and diagnostic role of hsCRP in stroke.

MATERIALS AND METHODS

The study consisted of 50 patients of acute stroke admitted in Gauhati Medical College and Hospital. The control population consisted of two groups - 50 age and sex matched controls with hypertension (Hypertensive control group) and 50 age and sex matched controls with no obvious disease constituted the Normal control group. hsCRP levels were measured in all the groups and compared statistically.

CONCLUSION

hsCRP is an acute phase reactant whose concentration rises in stroke as well as in those at risk. The rise may be identified even before the appearance of risk factors. Hence, hsCRP may be useful as a predictive and diagnostic marker in stroke.

Aldosterone Receptor Antagonism Reduces Urinary C-Reactive Protein Excretion in Angiotensin II-Infused, Hypertensive Rats

BACKGROUND

Elevated C-reactive protein (CRP) may contribute to elevated arterial pressure in Ang II-dependent hypertension. However, the in vivo effects of Ang II and of mineralocorticoid receptor (MR) antagonism on CRP during Ang II-dependent hypertension have not been examined. In addition, urinary CRP excretion as a method to monitor the progression of Ang II-induced inflammation has not been evaluated.

METHODS

Urine samples were collected from three groups (n = 10/group) of rats: 1) normotensive control, 2) angiotensin II infused (Ang II; 60 ng/min), and 3) Ang II + eplerenone (epl; 25 mg/d). A diet containing epl (0.1 %) was provided after 1 week of Ang II infusion.

RESULTS

After 28 d, Ang II increased SBP from 136 +/- 5 to 207 +/- 8 mmHg; this response in SBP was not altered following MR antagonism (215 +/- 6 mmHg). Ang II-infusion increased plasma CRP from 14 +/- 2 to 26 +/- 3 mug/mL and increased urinary CRP excretion nearly 8-fold (143 +/- 26 vs 1102 +/- 115 ng/d). Treatment with eplerenone reduced plasma CRP by 25 % and urinary immunoreactive CRP (irCRP) by 34 % in Ang II-infused rats suggesting that aldosterone contributes to the CRP-associated inflammatory response in Ang II-dependent hypertension.

CONCLUSIONS

The increase in SBP preceded the increase in irCRP excretion by at least 4 days suggesting that CRP does not significantly contribute to increased arterial blood pressure in Ang II-dependent hypertension. The blockade of MR reduced plasma CRP and urinary irCRP excretion demonstrating the contribution of aldosterone to the Ang II-induced generation of CRP. Furthermore, urinary CRP may serve as a non-invasive index for monitoring cardiovascular inflammation during hypertension.

Current analytical strategies for C-reactive protein quantification in blood

The measurement of serum C-reactive protein (CRP) levels has been given particular interest as a marker of inflammation associated with cardiovascular diseases. CRP belongs to the pentraxin family of proteins and the routine clinical analysis of CRP in blood samples is used as an important factor in primary prevention programmes together with causative and predisposing factors. This review focuses on the most representative methodologies and strategies for CRP detection and quantification that have been recently proposed, as well as reviewing those that are currently being developed for the specific, sensitive, inexpensive and high-throughput blood analysis of this protein.

Aptamer-antibody on-chip sandwich immunoassay for detection of CRP in spiked serum

This study describes a RNA aptamer-based biochip with high affinity and specificity for C-reactive protein (CRP). CRP, which exists in concentrations of 1-3mg/l in the serum of healthy patients, has been identified as a reliable biomarker for inflammation and as a potential marker for sepsis and tissue necrosis. The CRP-specific aptamer was covalently immobilized with its 5'-end on ARChip Epoxy. The detection of bound CRP was carried out optically using labelled secondary antibody in a sandwich format. Assay conditions were optimized with respect to the CRP binding buffer (buffer system, pH and additives) and Ca(2+) concentration (10 mM). Moreover, two sandwich immunoassay formats were tested, the one using dye-labelled antibodies and the other with biotin-modified antibodies/Dy647-labelled streptavidin. In comparison with an antibody-based chip assay, the aptamer chip is superior in terms of CRP measuring range (10 microg/l to 100mg/l) in human serum whereas antibody-based chips result in superior data reproducibility (CV of 8-15%). In contrast to antibody chips, aptamer microarrays provide the unique potential of detecting CRP in serum samples of low risk patients (1-3mg/l) as well as high risk patients (>500 mg/l), furthermore elevated CRP levels (20-350 mg/l) with acceptable recovery (70-130%) by including only one serum sample dilution step (1:100) for the complete measuring range.

Development of an optical RNA-based aptasensor for C-reactive protein

The development of a RNA-aptamer-based optical biosensor (aptasensor) for C-reactive protein (CRP) is reported. CRP is an important clinical biomarker; it was the first acute-phase protein to be discovered (1930) and is a sensitive systemic marker of inflammation and tissue damage. It has also a prognostic value for patients with acute coronary syndrome. The average concentration of CRP in serum is 0.8 ppm and it increases in response to a variety of inflammatory stimuli, such as trauma, tissue necrosis, infection and myocardial infarction. The interaction between the 44-base RNA aptamer and the target analyte CRP is studied. In particular, the influence of the aptamer immobilization procedure (chemistry, length, concentration), as well as the binding conditions, i.e., the influence on the binding of different buffers, the presence of Ca2+ ion and the specificity (against human serum albumin) have been evaluated. Using the best working conditions, we achieved a detection limit of 0.005 ppm, with good selectivity towards human serum albumin. Some preliminary experiments in serum are reported.

High sensitivity C-reactive protein: an emerging role in cardiovascular risk assessment

Coronary heart disease (CHD) is the major cause of death in the developed world and screening for conventional cardiovascular risk factors fails to identify more than 50% of the individuals who will present with acute coronary syndromes. Chronic inflammation appears to play a significant role in the initiation and development of atherosclerosis. Recent investigations have shown an association between inflammatory markers such as C-reactive protein (CRP) and CHD. These markers have proven useful as prognostic indicators in acute coronary syndromes and in predicting future coronary events in apparently healthy men and women. The availability of high sensitivity CRP (hs-CRP) assays has been crucial in exploring the role of this acute phase reactant in primary prevention settings. In this review, we discuss the evidence associating these inflammatory markers, especially CRP, with the pathogenesis of atherosclerosis and acute coronary syndromes, and we address the mechanism of risk as well as the clinical utility of this marker.

Levels of C-reactive protein in serum samples from healthy children and adults in São Paulo, Brazil

C-reactive protein (CRP) was measured by ELISA in the sera of 165 healthy blood donors and 125 normal children 1 to 14 years old. The serum levels of blood donors ranged from 0.05 to 57.6 mg/l with median and mean values of 1.8 mg/l and 4.86 mg/l, respectively. CRP levels ranged from 0.02 to 14.4 mg/l in the children's sera, the median being 0.45 mg/l and the mean 1.65 mg/l. No individual lacking CRP was detected. The high CRP levels observed in the present study suggest that the population of the State of São Paulo may usually be exposed to subacute infections and/or inflammation without presenting clinical symptoms.

The biological tests used in acute-phase of inflammation in bone infection : Clinical study

We present a comparative study of different biological tests in the acute phase of inflammation. The study was performed in 80 patients after surgical procedures in septic cases. We have compared the levels of C-Reactive Protein (CRP), C3, C3a, C4, T(o), sedimentation rate, and the leucocyte count. The analysis was made before surgery and every week until the ninth week after surgery. The variations in CRP which ocurred very early were extensive. The increase ranged between 200 and 600% after the surgical procedure. In cases without complications the CRP level returned to normal within 20 days. The study showed the CRP as the most specific and sensitive biological test of the acute phase of inflammation. However this biological test cannot differentiate between an acute infective and a severe inflammatory process.

Metabolic and scintigraphic studies of radioiodinated human C-reactive protein in health and disease

Plasma and whole-body turnover studies of human C-reactive protein (CRP), isolated from a single normal healthy donor and labeled with 125I, were undertaken in 8 healthy control subjects and 35 hospitalized patients including cases of rheumatoid arthritis, systemic lupus erythematosus, infections, and neoplasia. Plasma clearance of 125I-CRP closely approximated to a monoexponential function and was similar in the control and all patient groups. There was no evidence for accelerated clearance or catabolism of CRP in any of the diseases studied. The 19-h half-life was more rapid than that of most human plasma proteins studied previously, and the fractional catabolic rate was independent of the plasma CRP concentration. The synthesis rate of CRP is thus the only significant determinant of its plasma level, confirming the validity of serum CRP measurement as an objective index of disease activity in disorders associated with an acute-phase response. Approximately 90% of injected radioactivity was recovered in the urine after 7 d, and scintigraphic imaging studies with 123I-labeled CRP in 10 patients with different focal pathology showed no significant localization of tracer. The functions of CRP are thus likely to be effected predominantly in the fluid phase rather than by major deposition at sites of tissue damage or inflammation.

C-reactive protein in patients with lymphatic filariasis: increased expression on lymphocytes in chronic lymphatic obstruction

Levels of C-reactive protein (CRP) were evaluated by enzyme immunoassay in patients infected with the filarial parasite Wuchereria bancrofti. Significantly elevated levels of CRP (P less than 0.001) were demonstrated in patients with chronic lymphatic pathology (CP; n = 18) compared to patients with asymptomatic microfilaremia (MF; n = 13) and normal volunteers (NV; n = 29). Serum levels of CRP showed an inverse correlation (rs = -0.37; P less than 0.05) with phosphocholine (PC)-containing filarial antigen that was present in the circulation of patients with bancroftian filariasis. Marked elevations in the percentage of CRP-binding lymphocytes were observed in patients with CP (mean = 44%; P less than 0.001) compared to those with MF (mean = 18%) or NV (mean = 3%). The increased percentage of surface CRP was not due to an abnormal change in major lymphocyte subset (CD5, CD4, CD8, or CD19). No significant correlation was noted between surface CRP and serum CRP; however, an inverse correlation was observed between surface CRP and PC-bearing circulating filarial Ag (rs = -0.64; P less than 0.001). Biosynthetic labeling and immunoprecipitation with anti-CRP antibodies indicated quantitative differences in the synthesis of CRP in patients with CP compared to MF and CP. Complexing of CRP with PC-containing Brugia malayi antigen (CRP-BmA) caused increased binding to normal lymphocytes (less than 8%), but not close to the extent seen in patients with CP (44%), suggesting de novo synthesis of CRP in these patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Study of serum C-reactive protein concentration in cardiac failure

The serum concentration of C-reactive protein was prospectively assessed in 37 patients with various degrees of heart failure. The serum concentration of C-reactive protein was higher than normal in 26 (70%) patients. The concentration was directly related to the severity of heart failure and the stage of decompensation. Hepatic cell damage is the most likely stimulus to cytokine production and hence release of C-reactive protein in heart failure. Heart failure is an additional cause of raised serum concentration of C-reactive protein but the pathological importance of this feature is not yet known.

Influence of tuftsin-like synthetic peptides derived from C-reactive protein (CRP) on platelet behaviour

C-reactive protein (CRP) is an acute-phase reactant that modifies platelet function differently, depending upon its physiochemical state. Aggregated and ligand-complexed forms of CRP initiate the activation of platelets, whereas naturally occurring CRP peptides inhibit platelet activation. The present study documents neutral proteases of the polymorphonuclear leucocyte (PMN) to cleave CRP into reaction products with the potential to inhibit platelet activation, and explore the structure-function relationships involved in the regulation of platelet activation by CRP using synthetic CRP peptides. Evidence was obtained that (i) a minimum of two linear functional domains exist within CRP that influence platelet activation; (ii) they reside in the mid-portion and at the C-terminus of the CRP molecule; (iii) the mid-portion domain inhibits platelet activation stimulated by adenosine diphosphate (ADP) or acid-soluble collagen, whereas the C-terminal domain initiates platelet activation; (iv) the functional expression of the C-terminal domain is maximized when the linear peptide is immobilized on latex; and (v) both CRP domains contain a homologue of the immunoregulatory signal peptide, tuftsin. These data suggest that the molecular mechanisms by which platelet processes are modulated by CRP may be related to the presence of tuftsin homologues in CRP.

Studies of the in vivo synthesis and catabolism of serum amyloid P component (SAP) in the mouse

The production of mouse serum amyloid P component (SAP), a major acute phase protein of liver origin, was studied immunocytochemically using the peroxidase staining technique. SAP was not detectable in the cytoplasm of hepatocytes from normal, unstimulated mice, nor was it observed before 24 h after an acute phase stimulus. 125I-labelled mouse SAP was cleared from the plasma in vivo with a half-life of 7.0-8.25 h in all animals studied including: normal mice of different strains with different genetically determined plasma SAP concentrations; mice undergoing acute phase responses with greatly elevated plasma SAP levels and mice with casein-induced amyloidosis. The circulating level of SAP is thus independent of its rate of clearance and catabolism and is determined by the rate of synthesis and/or secretion of SAP.

Age related detection of tissue amyloid P in the skin

The presence of tissue amyloid P component in normal skin from fetuses and children was studied using direct, fluorescent, immunohistochemical techniques on frozen sections. Tissue amyloid P is not detected in fetuses or in children up to the age of 2 years but from the age of 4 years upwards it is readily detected and invariably present. Though the function of human amyloid P is unknown its role appears to be age or maturity related.

C-reactive protein as a detector of organic complications during recovery from childhood purulent meningitis

Twenty-eight bacteriologically proved episodes of purulent meningitis in 27 infants and children were monitored prospectively with sequential determinations of serum C-reactive protein. Except in one rapidly fatal case, all the patients showed decreasing CRP values for about 1 week. In five patients the CRP values than returned to a high level (P less than 0.001). Each of these patients developed an organic complication (subdural effusions in three, transient widening of the ventricles in one, purulent arthritis with osteomyelitis in one). Except for one infant with sensorineural hearing loss, which probably had developed early in the course of meningitis, no permanent sequelae were found in the patients with uncomplicated courses. One infant later had a relapse of Escherichia coli meningitis, reflected in a sharp increase of CRP. We conclude that sequential CRP measurements may be performed routinely to detect potential complications at an early stage of bacterial meningitis.

Invertebrate recognition protein cross-reacts with an immunoglobulin idiotype

To estimate the minimal structural requirements for cross-reaction of idiotypic determinants, we determined the capacity of monoclonal antibodies specific for the idiotype of the phosphorylcholine (PC)-binding myeloma protein TEPC-15 for cross-reactivities with the PC-binding, acute-phase protein C-reactive protein (CRP) and the hemagglutinin from the horseshoe crab Limulus polyphemus (limulin), which binds sialic acid and PC. Certain monoclonal antibodies (MAb) to the TEPC-15 idiotype showed strong cross-reactions with CRP and limulin when tested by enzyme-linked immunoadsorbent assays. The specificity of the cross-reactivities was confirmed by testing the binding of the reactive anti-TEPC-15 MAb to both CRP and limulin in the presence of p-nitrophenylphosphorylcholine (pNPPC), N-acetylneuraminic acid, and bovine submaxillary mucin. The binding of the MAb to both CRP and limulin was strongly decreased by pNPPC, partially decreased by free PC, and not affected by N-acetylneuraminic acid or bovine submaxillary mucin. Neither CRP nor limulin showed significant overall sequence homology to vertebrate immunoglobulins. However, CRP, limulin, and TEPC-15 variable region heavy chain (VH) shared short stretches of homology (8-10 amino acids) that mapped to a stretch comprised of the second complementarity determining region and third framework region of the TEPC-15 VH. These results might reflect either evolutionary convergence forced upon molecules of diverse evolutionary histories because of steric requirements of binding the same ligand, or a conservation of primitive combining site gene segments in evolution.

Acute phase proteins with special reference to C-reactive protein and related proteins (pentaxins) and serum amyloid A protein

The acute phase response among plasma proteins is a normal response to tissue injury and is therefore a fundamental aspect of many diverse disease processes. It probably usually has a beneficial net function in limiting damage and promoting repair but in some circumstances it may have pathological consequences. Sustained high levels of acute phase proteins and especially SAA are associated with the development of amyloidosis in some individuals. Increased concentrations of CRP may, by activating the complement system, contribute to inflammation and enhance tissue damage. Failure of the normal or appropriate CRP response may also possibly have deleterious effects. SAA is a polymorphic protein which is normally present only in trace amounts but which, during the acute phase response, becomes one of the major apolipoproteins associated with high-density lipoprotein particles. The function of apoSAA is not known but it must have considerable physiological significance apart from its role as the putative precursor of amyloid A protein fibrils. CRP and SAP have been very stably conserved throughout vertebrate evolution and homologous proteins are apparently present even in vertebrates. This strongly suggests that they have important functions although these have not yet been precisely delineated. The main role of CRP may be to provide for enhanced clearance of inappropriate materials from the plasma whether these are of extrinsic origin, such as microorganisms and their products, or the autologous products of cell damage and death. The interaction between aggregated CRP and plasma low-density lipoprotein may play a significant part in the normal function of CRP and may also have a role in lipoprotein metabolism, clearance, and deposition. SAP is a normal tissue protein as well as being a plasma protein. Aggregated SAP selectively binds fibronectin and this may represent an aspect of the normal function of SAP. The deposition of SAP in amyloid is evidently not a normal function but it is not known whether this deposition is involved in the pathogenesis of amyloid or whether it is merely an epiphenomenon. In any case immunohistochemical staining for SAP is useful in the diagnosis of amyloid, in investigation of glomerulonephritis, and in studying disorders of elastic tissue. Regardless of its physiological or pathophysiological functions, the assay of serum CRP is a valuable aid to clinical management in a number of different situations and in different diseases provided results are interpreted in the light of full clinical information.(ABSTRACT TRUNCATED AT 400 WORDS)

Radiometric ligand binding assay for C-reactive protein. Complexed C-reactive protein is not detectable in acute phase serum

A radiometric ligand binding assay for human C-reactive protein (CRP) was established using pneumococcal C polysaccharide (CPS) coupled to magnetizable cellulose particles as the solid phase ligand. Competition for binding to the solid phase between 125I-CRP and unlabelled CRP permitted detection of 30 micrograms/l of CRP and the precise assay of concentrations up to 3000 micrograms/l. Identical results were obtained when the assay was used to quantitate isolated pure CRP and pure CRP added to normal human serum. However in vitro addition of known ligands for CRP to acute phase serum resulted in lowering of the apparent CRP concentration in this assay and addition of as little as 1 microgram/l of free CPS or 1 mg/l of lecithin was demonstrable in this way. A combination of the ligand binding assay and the standard electroimmunoassay for CRP was therefore used to test acute phase sera for the presence of CRP complexed in vitro. No evidence of complexed CRP was detected among sera containing between 1-319 mg/l of CRP from patients with Hodgkin's disease (10), rheumatoid arthritis (10), Crohn's disease (19) and various microbial infections (11), including six with subacute bacterial endocarditis. Since it is likely that CRP does form complexes with its ligands in the plasma these results suggest that complexed CRP is rapidly cleared from the circulation.

C-reactive protein for rapid monitoring of infections of the central nervous system

Serum C-reactive protein (CRP) was measured nephelometrically or turbidimetrically for rapid differential diagnosis of sixteen bacterial and fifteen viral infections of the central nervous system in patients aged from 2 weeks to 49 years. On hospital admission CRP levels were far above the upper limit of normal (19 mg/l) in all patients with bacterial meningitis, regardless of the duration of illness, the age of the patient, the bacterium involved, fever, the erythrocyte sedimentation rate, or the cerebrospinal-fluid cell count. In contrast, a slight rise in CRP level was seen in only one case of viral meningitis. CRP was useful also in monitoring the clinical course of the illnesses and in the detection of subdural effusion in one patient with Haemophilus influenzae meningitis and of otitis media in another patient with coxsackie B meningitis. If no complications developed, CRP levels returned to normal within 7 days in the bacterial meningitis group. The rapid measurement of CRP levels is of importance and should be used more often in clinical practice.

Isolation and characterization of C-reactive protein and serum amyloid P component in the rat

C-reactive protein (RP) and serum amyloid P component (SAP) have been identified for the first time in rat serum and isolated by calcium-dependent affinity chromatography. Rat CRP closely resembled human CRP in its amino acid composition, in having five subunits per molecule and in its electron microscopic appearance as a pentameric annular disc. It differed, however, from all other mammalian CRP's characterised hitherto in being a glycoprotein bearing a single complex oligosaccharide on each polypeptide subunit. Furthermore one pair of tis subunits per molecule was linked by a interchain disulphide bridges whereas in other animals the subunits of both CRP and SAP are all non-covalently associated. The serum concentration of CRP in normal healthy laboratory rats and in specific pathogen-free rats was 300-600 micrograms/ml which is much greater than has been described in any other species and exceeds even maximal acute phase levels of CRP in man. Following injections of casein or croton oil, serum CRP levels rose to a maximum of about 900 micrograms/ml. Rat CRP bound to pneumococcal C-polysaccharide (CPS( but, in marked contrast to the behaviour of CRP from man, rabbit and marine teleost fish, it did not precipitate with CPS solutions, agglutinate CPS-coated sheep erythrocytes or initiate complement activation. Rat SAP, like SAP of other species, was a glycoprotein but unlike them it was composed only of a single pentameric disc not two such discs interacting face-to-face. The normal level of SAP in rat serum was 20-50 micrograms/ml, very similar to the levels seen in man, and it did not behave as an acute phase reactant in response to casein or croton-oil injections. In this respect it resembled human SAP but differed from murine SAP which is a major acute phase reactant.

Tuftsin, Thr-Lys-Pro-Arg. Anatomy of an immunologically active peptide

Tuftsin, a natural occurring tetrapeptide, has been found to exhibit several biological activities connected with immune system function. Although little is known about tuftsin's 'biogenesis', much information has been gleaned about its structure-function relationships, which have shown that several features of the molecule are essential for expression of full biological activity. Furthermore, specific receptor sites for tuftsin have been found to exist exclusively on phagocytic cells. Research indicates that tuftsin binding to target cells effect intracellular calcium and cyclic nucleotide levels. Implication of these facts on tuftsin's mode of action are discussed. Basic peptidic segments resembling tuftsin are found in a variety of regulatory peptides. Questions are, therefore, raised as to the biospecificity an cross-reactivity of these sequences. Substance P, one such peptide, which binds with and activates tuftsin receptors, is described. In light of tuftsin's therapeutic potential, assays for its determination have been introduced. When applied to analyze human blood serum of normal as well as of various pathological origins, direct correlation was found between tuftsin levels and susceptibility to bacterial infections.

C-reactive protein fifty years on

The discovery of C-reactive protein (CRP) half a century ago led to the description of the acute-phase reaction which is a fundamental response of the body to injury. Recent work on the structure and function of CRP has revealed the existence of a unique plasma protein family, including CRP and serum amyloid P component (SAP). These proteins have been conserved throughout vertebrate evolution. CRP binds specifically to a wide range of substances derived both from damaged autologous cells and from microorganisms. Complexed CRP can activate the complement system and, by virtue of its dramatically increased production in response to tissue injury, it probably acts primarily as a protective mechanism. However, in some circumstances CRP may also initiate or exacerbate inflammatory lesions. Clinical measurement of serum CRP is valuable as a screening test for organic disease and as a sensitive object index of disease activity and response to therapy in some inflammatory, infective, and ischaemic conditions. SAP closely resembles CRP in structure but not an acute-phase reactant in man. An apparently identical protein, amyloid P component (AP), is always found in amyloid deposits. AP is also found in normal tissues, as an integral constituent of vascular basement membranes and is located on the peripheral microfibrillar mantle of elastic fibres throughout the body.

Isolation of a phosphorylcholine-containing component from the turbot tapeworm, Bothriocephalus scorpii (Müller), and its reaction with C-reactive protein

A fraction isolated by electrofocusing (pI 4.2) from a saline extract of the turbot parasite, Bothriocephalus scorpii, contained choline and precipitated with a teleost C-reactive protein (CRP) and a phosphorylcholine-binding Balb/c mouse myeloma protein, TEPC-15. Non-dialysable products released from cultured tapeworms also precipitated with the phosphorylcholine-specific precipitins. Ca2+ was required for precipitation with CRP and immunodiffusion lines were confluent with pneumococcal C-polysaccharide and a fungal C substance. Intradermal injection of the phosphorylcholine-containing fraction caused an immediate erythema reaction in all mature turbot tested. The skin reaction is though to be related to the amount of circulating CRP and this protein was present in sera fro all nature turbot giving a positive skin response. There is no evidence for CRP being toxic to the tapeworms and the possibility is discussed that the worms exploit the host CRP for their own survival.

Amyloid P-component is a constituent of normal human glomerular basement membrane

Glomerular and other vascular basement membranes were found to contain an antigen that was immunochemically indistinguishable from serum amyloid P-component. There was no immunological cross-reactivity between antisera to serum amyloid P-component and to collagen types I, III, IV, or V. The amyloid P-component antigen was confined to the endothelial aspect, the lamina rara interna, of glomerular basement membrane. It could not be eluted by high-ionic-strength saline, EDTA, dithiothreitol, or either polar or nonpolar detergents, but was released into solution when isolated glomerular basement membrane was digested by highly purified bacterial collagenase. Most of these P-component molecules and their constituent polypeptide chains were of higher molecular weight and lower isoelectric point than serum amyloid P-component. These findings indicate that, as well as being a normal plasma protein and a universal constituent of amyloid deposits, P-component is also a normal matrix glycoprotein of basement membrane in which it is covalently linked to collagen and/or other matrix proteins. This may be relevant both to the pathogenesis of amyloidosis and to other aspects of physiology and pathology of basement membranes.