Marilyn L. Baltz

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)

PHYLOGENETIC ASPECTS OF C-REACTIVE PROTEIN AND RELATED PROTEINS*

C-reactive protein (CRP) was discovered by Tillett and Francis’ in the sera of patients with various infectious and inflammatory diseases as a material which precipitated pneumococcal C-polysaccharide (CPS). Subsequently Abernethy and Ave

Specific Chemical Dissociation of Fibrillar and Non-Fibrillar Components of Amyloid Deposits

characterized CRP as a protein and identified the requirement for calcium ions in its interaction with CPS, while they and established that the appearance of CRP in the serum is a nonspecific response to infection, inflammation and tissue damage. Abernethy and Averf also introduced the term “acute phase sera” to designate samples obtained from patients in the acute phase of infectious diseases. CRP was called the “acute phase protein” and this term was subsequently applied to the large number of other plasma proteins, the concentrations of which are raised in acute phase sera. At an early stage Abernethy’ reported the presence of a precipitin comparable to CRP in acute phase monkey serum and, although he had been unable to find any in mouse or rabbit sera, Anderson and McCarty’later described the existence

Calcium-dependent aggregation of human serum amyloid p component

In systemic amyloidosis, a fatal disorder for which there is no effective treatment, the extracellular protein deposits are composed of amyloid fibrils together with a non-fibrillar glycoprotein, amyloid P component (AP). Methyl 4,6-O-(1-carboxyethylidene)-beta-D-galactopyranoside (MO beta DG), a recently identified ligand for AP, was tested for its ability to produce in-vitro elution of AP which had been laid down with amyloid fibrils in vivo. Millimolar concentrations of MO beta DG completely dissociated AP from human and murine splenic amyloid deposits. Availability of this material thus provides for the first time the opportunity for specific molecular dissection of amyloid deposits. If MO beta DG or a related substance were effective in vivo it might be of therapeutic importance.

Mechanisms of Schistosoma mansoni egg excretion: Parasitological observations in immunosuppressed mice reconstituted with immune serum

Normal human serum or isolated human amyloid P component was ultracentrifuged on density gradients containing either 10 mM EDTA or different concentrations of Ca2+ between 0.15 and 2.15 mM. In the presence of Ca2+ concentrations of 1 mM or more human P component sedimented more rapidly than it did in the presence of lower Ca2+ levels or of EDTA. This phenomenon was due to Ca2+-dependent aggregation of P component molecules and did not require the presence of any other serum constituents. It was completely inhibited by incorporating a physiological concentration (40 mg/ml) of serum albumin in the gradients, suggesting that free ionized Ca2+ is required to promote aggregation of the P component. P component from the mouse and the plaice (Pleuronectes platessa L.), a marine teleost, did not undergo the same Ca2+-dependent aggregation as human P component. These observations resolve a discrepancy existing in the literature concerning the sedimentation rate of human P component in density gradient ultracentrifugation and shed new light on its behaviour with respect to Ca2+ which may be relevant to the deposition of P component in amyloidosis.

Isolation and characterization of goat C-reactive protein

Summary CBA mice which had been deprived of their T cells by a combination of adult thymectomy and injection of rabbit anti‐mouse thymocyte serum failed to excrete as many Schistosoma mansoni eggs in their faeces as immunologically intact controls. This failure of parasite egg excretion was not obviously attributable to any marked change in the amount of faecal matter produced, or to a change in the size of the worm burden, or to the number or distribution of eggs in the tissues as a result of T‐cell deprivation. S. mansoni eggs freshly isolated from T‐cell‐deprived mice and injected intravenously into normal animals, induced lung granulomas which were the same size as those induced by injection of eggs from normal donors. The rate of S. mansoni egg excretion was not affected by the density of eggs in the tissues, in as much as there was a linear relationship between the number of tissue‐bound eggs and the number of eggs detected in the faeces. Treatment of infected mice with the immunosuppressant hydrocortisone acetate also induced a marked reduction in the rate of egg excretion. Injections of serum derived from chronically infected normal mouse donors increased the rate of egg excretion in both T‐cell‐deprived and steroid‐treated mice, but the degree of reconstitution obtained by daily serum injections was only partial relative to normal egg excretion rates. Treatment of infected normal or deprived serum‐treated mice with cobra venom factor to reduce serum complement C3 levels had no effect on the rate of S. mansoni egg excretion.

Circulating immunoglobulins and complement in mice with Hymenolepis nana infection

A pentraxin was isolated from acute phase goat serum by its calcium-dependent affinity for agarose, and although it did not bind to phosphorylcholine immobilised on Sepharose, its binding to agarose was reversed by exposure to fluid phase phosphorylcholine. It was identified as goat C-reactive protein on the basis of its immunochemical cross-reactivity with human and bovine C-reactive protein. The molecule was composed of five identical, glycosylated, non-covalently associated subunits, each of molecular weight approx. 24,000. Acute phase serum levels in a small number of samples were not significantly different from normal levels (means 72 and 55 micrograms/ml, respectively), suggesting that goat C-reactive protein is not a major acute phase reactant. No other pentraxin was detected in goat serum.

Epileptic discharges produced in monkeys by injection of spleen cells from rabbits immunised with monkey brain

Abstract Changes in the circulating immunoglobulins and complement in ddY mice were assayed at various times after immunizing and challenge infections with Hymenolepis nana eggs. The levels of IgG1 and IgG2a consistently increased during 3–4 weeks after immunizing infection. The increase of these immunoglobulins after challenge infection was quicker and more intense than that following immunization. It was not possible to correlate increased levels of IgG1 and IgG2a with the onset of destruction of challenge larvae in immunized mice. IgM concentrations increased slightly during 4 days after immunization but challenge infection did not further increase IgM levels. IgA and IgG2b levels showed no significant change during the course of the infection. Serum C3 levels showed no discernible change after either immunizing or challenge infections. An attempt to specifically suppress the acquisition of resistance by administration of the complement-depleting agent, cobra venom factor (CoF), before immunization failed and depletion of complement activity with CoF that was administered just before challenge infection also failed to affect resistance. These results suggest that complement has no critical role in either induction of the response nor in the anamnestic response to H. nana infection in mice.

Serum amyloid P-component is an acute-phase reactant in the mouse.

Cell suspension from the spleen of rabbits immunised with monkey brain gave rise to epileptic discharges in the monkey when injected intracortically, except in the case of one injection from a rabbit not recently given a booster treatment. In contrast, cell suspensions from the spleen of unimmunised rabbits, or of a rabbit immunised with a non-brain material, in all cases failed to be effective. The epileptic discharges began about 2 weeks after injection, were variable in frequency, and lasted throughout the period of recording.