A heparin-precipitable fraction of human plasma. II. Occurrence and significance of the fraction in normal individuals and in various disease states

Analysis of cryoproteins with a focus on cryofibrinogen: a study on 103 patients

OBJECTIVES

Cryofibrinogen (CF) is an abnormal protein in plasma that precipitates at 4 °C and dissolves at 37 °C. Whilst serum cryoglobulins (CGs) analysis is common practice, CF investigation is rarely performed. This study aims to describe the testing methodology developed at our laboratory, potential pitfalls for all analytical phases, the distribution among hospital wards and clinical conditions underlying test requests and clinical conditions in which to order CF analysis is useful.

METHODS

Retrospective analysis of laboratory samples received between January 2019 and June 2021 with CF testing requests.

RESULTS

A complete protocol for CF pre-analytical, analytical and post-analytical phases are supplied. Most test requests were received from the rheumatology department for systemic sclerosis or liver transplant screening. Among the 103 in-patients included, CF+ was confirmed in 68 patients (66%). Of observed CF+ patients (n=68) most cases were CGs- (n=44, 67%). Isolated CF was found in 43% of the cases. Among CF- patients (n=35; 34%) only 2 patients had positive CGs (CGs+). Among rheumatology patients (n=66), isolated CF+ was observed in 45% (n=30/66), whilst among patients with systemic sclerosis with CF+ (n=19), isolated CF+ was detected in 79% (n=15/19).

CONCLUSIONS

Described analytical procedures may be used for the creation of harmonized recommendations and indications for CF analysis. Isolated CF positivity among hospitalized patients, predominantly rheumatology and systemic sclerosis patients, appears higher than rates previously reported in literature. We propose CF test recommendations should be included in investigation protocols for diseases where cryofibrinogenemia may occur.

Cryofibrinogenemia

Cryofibrinogenemia is a cryoprotein that was first identified in 1955 by Korst and Kratochvil. Unlike cryoglobulin, the precipitate forms only in plasma and not in the serum. The presence of cryofibrinogen in plasma can be asymptomatic. Cryofibrinogenemia is considered a rare disorder: its prevalence varies from 0% to 7% in healthy subjects and from 8% to 13% in hospitalized patients. Nevertheless, cryofibrinogenemia, when a cryopathy is clinically suspected, has been reported in 12% to 51% of patients. Skin manifestations are usually the first signs and are usually moderate; in addition, cold intolerance, Raynaud phenomenon, purpura, or livedo reticularis often occurs. Skin necrosis, acral ulcers, and gangrene can lead to surgery and amputation. Systemic manifestations are common, and arterial or venous thrombotic events are frequent. Cryofibrinogenemia may be primary (essential) or secondary to other underlying disorders, such as carcinoma, infection, vasculitis, collagen disease, or associated with cryoglobulinemia. The histological features of cryofibrinogenemia can confirm the presence of cryofibrinogen within small and medium arteries, plus occlusive thrombotic diathesis composed of eosinophilic refractile deposits within vessel lumina. Cryofibrinogenemia is a treatable and potentially reversible disease.In moderate forms, it can be treated by simply avoiding cold temperatures. The use of corticosteroids in association with low-dose aspirin is the treatment of choice for moderate forms, although stanozolol is an alternative maintenance therapy. Immunosuppressive therapies, plasmapheresis, and/or intravenous fibrinolysis are useful at treating severe forms of cryofibrinogenemia. The use of anticoagulants is limited to the management of thrombotic events. Treatment of secondary cryofibrinogenemia involves the management of associated diseases. Regular follow-ups are needed because of the high risk of recurrence. Moreover, up to half of patients with cryofibrinogenemia considered as essential may develop lymphomas in the following years. Compared with cryoglobulinemia, less is known about cryofibrinogenemia. Its diagnosis should be considered when suggestive clinical manifestations are present and when there are specific biopsy findings. Although identification of cryofibrinogen in blood samples is simple and inexpensive, cryofibrinogenemia can be asymptomatic, and a lack of diagnosis criteria can make diagnosis difficult to confirm. This review describes the clinical manifestations and the biological and pathological features and discusses the criteria used to diagnose and manage cryofibrinogenemia.

Significance of cryoprofibrin in fibrinogen-fibrin conversion

Fibrinogen altered by thrombin-catalyzed liberation of fibrinopeptide A was found to combine with native fibrinogen to form a cold-precipitable complex we have called "cryoprofibrin." The altered fibrinogen lacking fibrino-peptide A polymerized into fibrin, but not until conditions for equilibrium between its incorporation into both cryoprofibrin and fibrin were satisfied. At equilibrium, the concentration of cryoprofibrin was maintained at a threshold proportional to the concentration of fibrinogen. When the concentration of cryoprofibrin was below threshold, fibrin could be depolymerized and solubilized by fibrinogen with resultant formation of cryoprofibrin. Since threshold concentrations of cryoprofibrin appear necessary for precipitation of fibrin, the concentration of cryoprofibrin in plasma provides a basis for determining intravascular deposition of fibrin. Intravascular deposition of fibrin does not appear to occur normally in rabbits, because the concentration of cryoprofibrin in plasma from normal rabbits is far below the threshold for precipitation of fibrin. The applicability of cryoprofibrin as an indicator of fibrin deposition is demonstrated by the occurrence of levels of cryoprofibrin approaching the threshold for precipitation of fibrin in plasma from endotoxin-treated rabbits. The current concept that the fibrinogen molecule can dissociate into subunits can be used to explain the conversion of fibrinogen to cryoprofibrin. As one possibility, the two residues of fibrinopeptide A contained in fibrinogen may be located on two separate subunits of the molecule; cryoprofibrin is produced when one of these subunits is replaced by a subunit altered by loss of fibrinopeptide A. Recombination of native subunits with subunits altered by loss of A would counter dissociation of cryoprofibrin and inhibit polymerization of subunits lacking fibrinopeptide A. As an alternate mechanism, two residues of A may be liberated concurrently from a single subunit. Cryoprofibrin would then correspond to a fibrinogen molecule, containing a subunit with two residues of A, in combination with an altered molecule containing a subunit lacking two residues of A. Liberation of fibrinopeptide B did not contribute measurably to production of fibrin resulting from limited action of thrombin on rabbit fibrinogen. Both fibrin containing B but not A, and fibrin containing neither B nor A, as is produced by extensive action of thrombin, could be solubilized by fibrinogen. Thrombin, or another enzyme utilizing tosyl-L-arginine methyl ester as substrate, appeared reversibly to inhibit polymerization of fibrin containing fibrinopeptide B. This enzyme and fibrinogen were the only proteins appearing to inhibit polymerization in plasma from normal rabbits.

THE PATHOGENIC ROLE OF FIBRIN DEPOSITION IN THE GLOMERULAR LESIONS OF TOXEMIA OF PREGNANCY

An immunofluorescent study of renal biopsies from patients with toxemia of pregnancy has been performed. It was found that the glomeruli consistently showed bright staining for fibrin within endothelial cells, as well as occasional deposits along the basement membrane. Gamma globulin was only occasionally demonstrable, generally in the form of irregular deposits along the basement membrane. β_1C was absent and albumin was not seen in glomeruli, except sometimes in the form of droplets within epithelial cells. In biopsies from pregnant patients without toxemia only equivocal staining for fibrin was seen. On the basis of these observations and other evidence discussed, it is proposed that the accumulation of fibrin in glomeruli reflects a prolonged state of intravascular clotting in toxemia and that the arrest in glomeruli of some form of circulating fibrin constitutes the basic pathogenic mechanism of the glomerular damage in this disease.

Dynamic light scattering studies on hydrodynamic properties of fibrinogen-fibronectin complex

A high molecular weight 'cryogel' was obtained as insoluble complexes by cold incubation at near-freezing temperatures from heparinized plasma of patients with rheumatoid arthritis. After the cryogel was solubilized at 37 degrees C, 1:1 complex of fibrinogen and fibronectin was purified at room temperature by affinity chromatography on a gelatin-Sepharose 4B. Hydrodynamic properties of the complex were investigated as a function of temperature and NaCl concentration using a dynamic light scattering. The diffusion coefficients of the complex at 20 degrees C decreased with increasing of NaCl concentration as free fibronectin. The complex appears to be a more compact form at low ionic concentration, which is associated with conformational changes of fibronectin. The diffusion coefficient of the complex at 20 degrees C in 0.05 M TrisHCl(pII7.4) containing 0.5 M NaCl was estimated as 8.5 x 10(-8) cm2s-1. The complex did not dissociate over the temperature range from 20 to 37 degrees C. The diffusion coefficients of the complex decreased significantly at 12 degrees C and 40 degrees C. The thermal denaturation of fibrinogen molecule in the complex was observed at 40 degrees C. The CONTIN analysis of the light scattering data showed that the complex associated to form higher aggregates at 15 degrees C, but not at near-freezing temperature. The equilibrium between the complex and higher aggregates appeared reversible.

Thrombotic vasculopathy associated with cryofibrinogenemia

Cryofibrinogenemia refers to the presence of cold-precipitable plasma proteins associated with a variety of disorders, including malignancies, inflammatory processes, and thrombohemorrhagic phenomena. Few cases of essential or primary cryofibrinogenemia are reported. We report a case in a 48-year-old man of essential cryofibrinogenemia and hemorrhagic necrosis of the ears and of the upper and lower extremities. Histopathologic studies demonstrated extensive eosinophilic thrombi in the dermal vasculature, with minimal inflammation and no vasculitis. Cryofibrinogenemia should be considered in the investigation of patients with otherwise unexplained cold intolerance and dermal thrombosis associated with minimal or no inflammation.

Evidence that changes in fibrinogen quality during acute phase reactions are of major importance for the amount of heparin precipitable fraction (HPF)

The influence of qualitative and quantitative changes in plasma fibrinogen upon the amount of heparin precipitable fraction (HPF), obtained during the course of acute disease states, were examined. Whereas fibrinogen in plasma includes 3 species of different molecular weights (HMW, LMW, LMW'), fibrinogen in HPF, from normal as well as from "acute phase" plasma, consisted almost exclusively of HMW-fibrinogen (3% SDS-PAGE). Sub-unit chain electrophoresis (10% PAGE-SDS and two-dimensional electrophoresis) did not disclose any signs of abnormalities in the fibrinogen precipitated in HPF. Studies on patients revealed that the composition of plasma fibrinogen changed (increased HMW) during the course of acute myocardial infarction and following hip operations, and indicated that the amount of HPF was governed by the relative amount of HMW-fibrinogen as well total fibrinogen. This assumption was strengthened by quantitating the amount of HPF obtained after addition of highly purified HMW and LMW fibrinogen to normal and "acute phase" plasma. It is concluded that fibrinogen quality (per cent HMW or HMW/LMW ratio) is of major importance for the amount of HPF, thereby explaining some of the HPF-variations seen during the course of acute diseases.

Does qualitatively altered fibrinogen contribute to the increased heparin precipitable fraction (HPF) in acute myocardial infarction (AMI)?

The amount and protein composition of heparin precipitable fraction (HPF), and the plasma concentrations of fibrinogen, fibronectin, alpha 1-acid glycoprotein, alpha 1-antitrypsin, haptoglobin and C-reactive protein (CRP) were determined in healthy subjects as well as during the course of acute myocardial infarction (AMI). In all samples tested, HPF consisted nearly exclusively of fibrinogen and fibronectin. In the small precipitates from healthy subjects, approximately equal amounts of these two proteins were recovered. During the first days of AMI, plasma fibrinogen increased 2-3 fold. At the same time, however, the amount of HPF increased 5-10 fold. This increase was associated with increased precipitation of fibrinogen, whereas no simultaneous increase in fibronectin was found. In fact, a slight drop in plasma as well as HPF-fibronectin was regularly observed during this period. During the following week HPF returned to normal values, whereas the plasma fibrinogen remained elevated. No satisfactory explanation for this discrepancy can be offered at present. Thus, no evidence could be provided that other acute phase proteins than fibrinogen itself were involved. Some experiments, however, indicated qualitative changes in the fibrinogen participating in the HPF precipitation. Further studies are necessary to clarify this point. Such studies are in progress.

Fibronectin concentration in plasma of patients with breast cancer, colon cancer, and acute leukemia

Plasma fibronectin was measured in patients with breast cancer, colon cancer, and acute leukemia. In the patients with solid tumors, mean levels were significantly elevated above the mean level of age- and sex-matched normals whether the disease was thought to be metastatic or not (P less than 0.001). It did not make a difference whether the determinations were done prior to or during chemotherapy. Fibronectin was measured serially in eight hospitalized patients with leukemia during intensive induction chemotherapy. Normal concentrations were found prior to therapy. However, fibronectin concentration fell on the day following chemotherapy in nine of 12 episodes (P less than 0.05), and during sepsis in 13 of 13 episodes (P less than 0.001). Thus, the concentration was influenced by at least two factors: recent chemotherapy and sepsis. Because fibronectin concentration is sensitive to clinical events other than the status of the malignancy, it seems unsuitable as a tumor marker, at least as a single isolated measurement.

Immunohistochemical study of fibronectin in human glioma and meningioma

The presence of fibronectin (FN) and glial fibrillary acidic protein (GFAP) in two astrocytomas, 17 glioblastomas, and five meningiomas was studied by indirect immunoperoxidase staining of formalin-fixed and paraffin-embedded surgical specimens. Angiogenesis in tumor was scored by the microscopic angiogenesis grading system (MAGS), and plasma FN levels were measured by single radial immunodiffusion. In astrocytomas and glioblastomas, GFAP-positive tumor cells had no FN expression and FN was confined to proliferating vessel walls and the leptomeninges, showing a mutually exclusive FN and GFAP expression. GFAP-positive tumor cells were occasionally surrounded by a network of FN-positive matrix produced by cells derived from the leptomeninges or blood vessels. In meningiomas, FN expression was found in vessel walls and meningioma cells including whorl formations and psammoma bodies. In general, deep immunoperoxidase staining for FN was shown in the endothelial cells and the psammoma bodies. Plasma FN levels were correlated significantly not to the degree of leptomeningeal proliferation but to the MAGS scores in gliomas.

Hematologic and serologic studies in 6-sulfanilamidoindazole arthritis

6-sulfanilamidoindazole (6-SAI), an antibacterial sulfonamide, is known to cause an acute, self-limited inflammatory reaction in the hind paws of older rats. Administration of 6-SAI results in hyperfibrinogenemia which precedes the onset of clinical arthritis. The hyperfibrinogenemia is associated with the prolongation of dilute blood clot lysis times, appearance of heparin-precipitable fibrinogen, elevations in fibrin degradation products, and complement titers and serum electrophoretic pattern changes that consist of decreased albumin concentrations and increased beta globulin concentrations. Alterations in 6-SAI medicated young rats are less marked and require higher doses.

Interactions among heparin, cold-insoluble globulin, and fibrinogen in formation of the heparin-precipitable fraction of plasma

Fibrinogen and the cold-insoluble globulin of plasma (CIg) are the main protein components of the heparin-precipitable fraction of normal plasma. The interactions among these proteins and heparin were examined. Heparin formed a cold-precipitable complex with purified CIg or with mixtures of CIg and fibrinogen but not with purified fibrinogen alone. Cryoprecipitation was augmented by addition of Ca(++) or by selection of optimal heparin levels; it was reduced or even abolished by raising the ionic strength or pH or both, or by raising the heparin concentration above that for maximum precipitation of CIg. Fibrinogen reduced the threshold for heparin-induced CIg cryoprecipitation and, by coprecipitating with heparin and CIg, increased the amount of precipitate that formed. In contrast to the heparin-precipitable fraction of normal plasma which contained both fibrinogen and CIg, that from a patient with congenital afibrinogenemia contained CIg but lacked fibrinogen. Normal plasma depleted of CIg by immunoabsorption failed to form a heparin-induced cryoprecipitate. Thus, CIg is essential for heparin-induced cryoprecipitation to occur. Fibrinogen, as assessed by chromatographic experiments with heparin-Sepharose columns, had a considerably lower binding affinity for heparin than did CIg, suggesting that it participates in precipitate formation mainly, if not entirely, by virtue of its affinity for CIg. The region of the fibrinogen molecule accounting for its precipitation with CIg appears to be localized in the carboxy-terminal segment of the Aalpha-chain; fibrinogen subfractions lacking this region failed to augment cryoprecipitation of heparin-CIg mixtures and, even though such species were present in normal plasma, they failed to coprecipitate in the heparin-induced complex.

The role of coagulation and fibrinolysis in the development of rabbit Masugi nephritis

The role of coagulation and fibrinolysis in the pathogenesis of rabbit Masugi nephritis was studied. Fibrinolytic activity of urine decreased rapidly to the minimum values at the peak of the disease. Histologic observations showed a severe proliferative glomerulonephritis. Immunofluorescent studies revealed localization of rabbit gamma globulin along the glomerular basement membrane in a typical linear pattern. Fibrin was positive in glomeruli not only within fibrinoid deposits, but also often diffusely in the places where no obvious fibrin was detected in histologic sections. Bright strands of fibrin was present between the cells forming a cresent. Electron microscopy indicated accumulation of fibrinoid materials beneath the endothelium. The basement membrane was damaged by the deposition of fibrinoid and followed by massive escape of intracapillary contents into the Bowman's space. Abundant fibrin and fibrinoid were seen in newly formed "monocytic-epithelial" crescents. Todd's fibrinolysis autography revealed diminished fibrinolytic activity in the severely affected glomeruli. Treatment with heparin prevented crescent formation and glomerular disorganization, while treatment with t-AMCHA increased fibrin and fibrinoid deposition and aggravated the glomerular injuries. It was concluded that the coagulation-fibrinolysis system could play an important role in the course of rabbit Masugi nephritis.

Circulating immunoglobulin complexes in Wegener's granulomatosis

Two cases of Wegener's granulomatosis are reported in which circulating immunoglobulin complexes detected during the active phase of the disease disappeared during induction of remissions of active pulmonary and renal disease by immunosuppressive agents. Elevated antiglobulin activity, urinary immunoglobulin L-chain concentration and evidence of activated coagulation mechanisms were also present during active disease, and returned toward normal with treatment. Studies showed that the serum complexes did not contain deoxyribonucleic acid (DNA) and demonstrated their immunoglobulin nature. Serum complement concentrations were normal, and no cryoglobulins were present. Immunofluorescent staining and electron microscopy of the kidney biopsy specimen of one patient showed marked fibrin deposition but no immunoglobulin or antigen-antibody deposits. Although the role of circulating immunoglobulin complexes in the pathogenesis of Wegener's granulomatosis remains uncertain, serial changes in the described parameters may provide an objective guide to activity of the disease and its response to treatment.

Factors influencing prognosis in the surgery of peripheral vascular disease: platelet adhesiveness, plasma fibrinogen, and fibrinolysis

A study of 76 patients having aorto-iliac (46) and femoropopliteal (30) surgery for atherosclerosis has shown a significant correlation between increased platelet adhesiveness, prolonged clot lysis, and failure of the reconstruction between 3 months and 5 years after operation. In addition, a raised plasmafibrinogen level, persisting 1 year after reconstruction, is often associated with failure. Patients having predominantly femoropopliteal disease show a significantly higher plasma-fibrinogen level than those with localized aorto-iliac disease. This correlation is such that when a high plasma-fibrinogen level is found in a patient with the clinical features of aorto-iliac disease it may be inferred that the femoropopliteal segment is also involved.