Detection of anti-vascular endothelial cell antibodies with microcytotoxicity testing

Antivascular endothelial cell antibodies (anti-VEC) were detected in 20 out of 20 serum samples from post renal transplant nephrectomy patients using a microcytotoxicity (MET) test, but in only 1 of 100 healthy blood donors. Cytotoxicity to VEC could occur in the absence of lymphocytotoxic antibodies. In this paper factors influencing the specificity and sensitivity of microcytotoxicity on vascular endothelial cell (VEC) were studied, including improvements in the preparation of VEC from an umbilical cord vein to get 95% and more of purity and viability; adequate dilution of rabbit sera to reduce its nonspecific VEC cytotoxic effect; and results read by exactly adjusted phase contrast microscopy to reduce the percentage of false negative. The original titers of allotypic and monoclonal antibodies against VEC have been shown to be reproducible in repeated testing during the past two years. The recognition of the weak cytotoxic effects of anti-HLA on VEC makes possible direct application of microcytotoxicity on VEC, to detect anti-VEC and to study VEC antigen classification (through a comparison of the cytotoxic effects of tested sera on VEC and concordant lymphocytes).

Amino acid sequence of a short chain neurotoxin from the venom of banded krait (Bungarus fasciatus)

The amino acid sequence of a short chain neurotoxin obtained from Bungarus fasciatus venom consists of 64 amino acid residues: Arg-Ile-Cys-Leu-Asn-Gln-Gln-Gln-Ser- Thr-Pro-Glu-Asp-Gln-Pro-Thr-Asn-Gly-Gln-Cys-Tyr-Ile-Lys-Thr-Asp-Cys-Gln- Asn-Lys - Thr-Trp-Asn-Thr-His-Arg-Gly-Ser-Arg-Thr-Asp-Arg-Gly-Cys-Gly-Cys-Pro-Lys- Val-Lys - Pro-Gly-Ile-Asn-Leu-Arg-Cys-Cys-Lys-Thr-Asp-Lys-Cys-Asn-Glu. The above result was obtained primarily from the amino acid analyses and sequencing of tryptic peptides accompanied with the necessary analyses and sequencing of the chymotryptic and lysyl endopeptidic peptides for alignment.

Studies of the coagulation system in arenaviral hemorrhagic fever: experimental infection of strain 13 guinea pigs with Pichinde virus

Significant coagulation abnormalities were associated with experimental infection of strain 13 guinea pigs with Pichinde virus, an arenavirus related to the virulent human pathogens Junin, Machupo, and Lassa viruses. Infected animals developed decreased activity of multiple coagulation factors, decreased antithrombin III levels, high levels of fibrin-fibrinogen degradation products, impaired platelet function, and thrombocytopenia. Testing for the presence of a coagulation inhibitor revealed a pattern consistent with factor deficiency. Fibrin thrombi were not found at necropsy. The findings of high fibrin-fibrinogen degradation product levels and decreased antithrombin III levels, in association with decreased activity of multiple coagulation factors and thrombocytopenia, suggest that intravascular coagulation is a feature of this experimental infection. The demonstration of abnormal platelet function is also significant, as this could contribute to defective hemostasis despite the moderate thrombocytopenia which usually occurs in arenaviral disease.

Acute hypoxemia does not increase blood fibrinolytic activity in man

The influence of acute hypoxemia on blood fibrinolytic activity was investigated in 12 healthy males. Physiologically significant hypoxemia was produced by inspiration of 13% oxygen for 30 min. Six healthy males were exposed to hypoxemia at rest and 6 males to hypoxemia during exhaustive physical exercise on an ergocyclometer. During control experiments both groups of health males inspired 21% oxygen. In 5 patients with manifest respiratory insufficiency the effect of hypoxemia at rest was studied during withdrawal of oxygen treatment for up to 2.5 hours. No increase in fibrinolytic activity (measured with euglobulin clot lysis and fibrin plates) due to hypoxemia was observed either in resting healthy males or in patients. In healthy males the increase in fibrinolytic activity after physical exercise at 13% oxygen was even somewhat lower compared to 21% oxygen. No changes in other hemostatic parameters (activated partial thromboplastin time, factor VIII-related antigen, fibrinogen, plasminogen, alpha-2-antiplasmin, fibrin(ogen) degradation products) that could be attributed to hypoxemia, were observed in any group tested. It was concluded that short-term acute hypoxemia does not increase blood fibrinolytic activity in man.

Progressive exposure of E-neoantigen associated with degradation of crosslinked fibrin by plasmin in vitro

Fragment E-neoantigen (Eneo) is a specific marker of structural and conformational changes associated with the degradation of fibrinogen and its related proteins. In this study Eneo expression was followed during the plasmin degradation of crosslinked (XL) fibrin in vitro, utilizing double antibody radioimmunoassay. Eneo was progressively exposed as degradation proceeded and its expression was associated with the liberation of high molecular weight fragments from XL-fibrin, their degradation into fragments DD and E, and the partial degradation of fragment E itself. An isolated protein fraction containing early high molecular weight fragments (MW greater than 360 000 d) and a fraction containing fragments YY and DY expressed approximately 170 times and 15 times less Eneo per protein respectively compared to the fragment E standard. XL-fibrin fragment E isolated from 1-hr plasmin digest expressed approximately 8 times less Eneo than fragment E isolated from 24-hr digest, indicating increased exposure of Eneo during fragment E degradation. Eneo expression of this terminal fragment E was comparable to fibrinogen fragment E. As expected, fragment DD had no Eneo immunoreactivity.

Radioimmunoassay of fragment E-related neoantigen: validation studies and clinical application

Measurement of fibrinogen-fibrin degradation products (FDP) levels in plasma may provide a direct index of plasmin action, and increased levels of FDP would indicate coagulopathy. We have established an E-neoantigen radioimmunoassay ( Eneo RIA) that can determine normal and pathological plasma levels of E-related FDP. The assay employs rabbit antiserum produced against fragment E derived from a plasmin digest of fibrinogen and subsequently absorbed with fibrinogen. The absorbed antiserum contains antibodies which are equally reactive with fibrinogen derived E (Fg-E) and fibrin derived E (Fb-E) but not with fibrinogen at 1 mg/ml. The Eneo RIA was validated by assay parallelism and by recovery experiments. Plasma Eneo immunoreactivities in 14 normals were 4-22 ng/ml (mean 12.7 ng/ml). Plasma Eneo levels in 23 of 24 patients with neoplastic and haematological diseases were elevated above normal (range 27-2027 ng/ml). Unusually high Eneo values were observed with three patients whose diseases were complicated by either disseminated intravascular coagulation (DIC) or deep vein thrombosis. After heparin therapy, the Eneo level of a patient with chronic DIC declined. A pathological plasma was eluted from a Sephadex G-200 column and Eneo immunoreactivity was determined on the eluates. The gel filtration pattern of Eneo indicates that E-related FDP is a family of plasmic fragments derived from crosslinked fibrin.

Comparisons of hemagglutination inhibition, staphylococcal clumping, and latex agglutination tests for canine fibrinolytic degradation products

Two assay systems for fibrinogen-fibrin degradation products (FDP) in canine serum, the glutaraldehyde erythrocyte hemagglutination-inhibition immunoassay (GEHII) and the staphylococcal clumping test (SCT), were compared for reactivity with the plasmin digests of canine fibrinogen and with sera obtained from dogs suspected of having circulating FDP, The GEHII reacted well with early and late plasmin digests of fibrinogen. With early-stage fibrinogen digests, the SCT was more reactive than was GEHII. However, after the appearance of D and E fragments in the digests, SCT reactivity decreased progressively during plasminolysis. The sensitivities of GEHII and SCT for assaying FDP were 0.5 and 0.125 microgram of fibrinogen equivalent/ml, respectively. Serum FDP values for dogs with desease were comparable, with values ranging from 1 to 122 micrograms/ml by GEHII and 8 to 64 micrograms/ml by SCT. One dog with fulminating disseminated intravascular coagulation had a serum FDP value of 128 micrograms/ml by SCT and 179 micrograms/ml by GEHII. Howeever, normal canine sera had values by SCT of 4 to 16 micrograms of fibrinogen equivalent/ml, whereas normal values by GEHII were 0.5 to 2 micrograms/ml. Serum FDP concentrations were also determined for healthy and diseased dogs by latex-agglutination test. The dog with fulminating disseminqated intravascular coagulation had a FDP value of greater than 40 micrograms/ml, and only 1 other diseased dog had greater than 10, but less than 40 micrograms of fibrinogen equivalent/ml. All other dogs were considered negative, with FDP values of less than 10 micrograms/ml.

Comparative sensitivity of two hemagglutination inhibition immunoassays for fibrinolytic degradation products in human serum

A new modification of hemagglutination inhibition immunoassay for measuring fibrinogen/fibrin degradation products (FDP) using glutaraldehyde as a coupling reagent was introduced. This method was compared with the tanned-red-cell hemagglutination inhibition immunoassay (TRCHII). Sheep erythrocytes (SRBC) were sensitized with fragment D or E, respectively. The procedure of sensitizing SRBC is simple and can be achieved within 2 hrs. The sensitized SRBC stored at 4 degrees C for 6 months did not lose their activities. The sensitivities for assaying D and E relative FDP were 0.32 mug/ml, respectively, which were slightly better than those of TRCHII. This represents the first adaptation of glutaraldehyde erythrocyte hemagglutination inhibition immunoassay (GEHII) for the estimation of FDP employing either microtiter plate or test tube. The microtechnique and test tube method were found to be essentially equivalent. The FDP level in the sera of normal individuals and patients suspected of elevation of FDP were assayed by both TRCHII and GEHII. By linear least squares analysis, the results show a significant correlation between these two methods. These results indicate GEHII is a simple, rapid and sensitive immunoassay for FDP in human serum.

Ultrastructural localization of gamma-chain and immunoglobulin G in human lymphocytes using enzyme-labeled Fab fragment

By the use of rabbit antibodies against the heavy chain of human immunoglobulin G (IgG), the gamma-chain and IgG molecules were successfully localized at the ultrastructural level in human peripheral lymphocytes. The rabbit Fab fragment was coupled to horseradish peroxidase by means of glutaraldehyde and the resulting conjugate could penetrate the intact plasma membrane. Discernible reaction product was observed in cisternae of the nuclear envelope, rough endoplasmic reticulum and Golgi apparatus as well as on the surface of the lymphocytes. In normal human individuals under no specific antigenic stimulation, only a few peripheral lymphocytes showed a rare positive intractoplasmic reaction. Reaction product may represent either the whole IgG molecule, the half molecule consisting of one heavy and one light chain or nascent gamma-chain.

Characterization of the terminal degradation products of canine fibrinogen by plasmin

Fibrinogen, isolated from canine plasma by the successive procedures of (1) freezing and thawing, (2) fractional precipitation with 25% saturated (HN4)2SO4 and (3) Sepharose 6B gel-filtration, had a molecular weight of 282 000 by the rapid sedimentation equilibrium method. However, a molecular weight for canine fibrinogen of 332 000, which is closer to that reported for human and bovine fibrinogens (340 000 plus or minus 20 000), was obtained from the sum of the molecular weights of the Aalpha, Bbeta and gamma chains, determined from dodecylsulfate gel electrophoretic patterns of reduced fibrinogen. Canine fibrinogen, subjected to proteolysis by urokinase-activated plasminogen for 24 h, contained degradation fragments D and E which were isolated by starch block electrophoresis and Sephadex G-200 gel-filtration. The purified D and E fragments with sedimentation coefficients of 5.0 S and 2.5 S had weight average molecular weights of 89 000 and 42 000, respectively by the rapid sedimentation equilibrium method. The ratio of D to E was 2:1 per parent fibrinogen molecule. Antigenic analysis according to anti-fibrinogen antiserum showed that both D and E fragments were antigenically deficient to native fibrinogen and revealed a reaction of non-identity with each other. Upon immunoelectrophoresis at pH 8.2, D and E had different electrophoretic mobilities. Preliminary studies indicate that based on thrombin time alone, D has anticoagulant activity while E appears to be a coagulation potentiator. Canine fibrinogen apparently consist of two core fragments with dissimilar chemical characteristics in common with the fundamental structures of human and bovine fibrinogens.