Monoclonal antibodies to fibrinogen: modulation of determinants expressed in fibrinogen by gamma-chain cross-linking

A method for the determination of the affinity constant of antibodies to tissue plasminogen activator

A simple method for the determination of the affinity constant of antibodies to fibrin-bound tissue-type plasminogen activator (t-PA) is described. The method is based on the high-affinity binding of t-PA to a solid-phase fibrin support which allows the specific separation of t-PA present in any biological fluid. This provides as in the physiological fibrin-t-PA interaction, a molecular structure conserving its antigenic and functional properties which allows for the binding of specific anti-t-PA antibodies and hence facilitates the separation of free from bound antibody. Then, antibodies bound to t-PA are revealed with a labelled, second antibody and data relating Bound v Total antibody input can be analyzed. Affinities were calculated by least square nonlinear regression analysis using a computerized approach. The method allows the direct use of plasma or other crude sources where t-PA is present in its most native form.

Monoclonal antibodies to crosslinked fibrin degradation products (XL-FDP). I. Characterization and preliminary evaluation in plasma

Monoclonal antibodies (mabs) were raised against X-oligomers, the earliest soluble fragments released from crosslinked fibrin (XL-FN), by the action of plasmin. Two of the mabs (NIBn 52 and NIBn 123) were monospecific for X-oligomers in that they showed no binding to fibrinogen, the plasmic fragments of fibrinogen (D and E) and non-crosslinked fibrin (X, Y, D and E), or the terminal digestion product of XL-FN, fragment DD-E. One other mab (NIBn 178) was panspecific for X-oligomers in that it exhibited a weak affinity for fibrinogen. The mabs were used to develop a two-site immunoradiometric assay (IRMA) and an enzyme-linked immunospecific assay (ELISA) which permitted the specific measurement of X-oligomers directly in plasma, rather than in serum. This immunoassay is a true assay of fibrinolysis as distinct from fibrinogenolysis and may be a potential aid in the diagnosis and evaluation of thrombosis. In preliminary studies, the assay detected low levels of X-oligomers in normal plasma and elevated levels in patients with disseminated intravascular coagulation.

Evidence for two functionally different fibrinogen receptors on hemopoietic cells: the glycoprotein IIb-IIIa and the mitogenic fibrinogen receptor

We have previously established that the mitogenic effect of fibrinogen on hemopoietic cell lines Raji and JM is mediated via a specific receptor (Levesque, J.-P. et al.: Proc. Natl. Acad. Sci. USA 83:6494-6498, 1986). In this study, we have further characterized the fibrinogen domain involved in the binding to the mitogenic receptor. This binding was not inhibited either by a monoclonal antibody against the C-terminal sequence of the fibrinogen gamma chains or by synthetic peptides containing the Arg-Gly-Asp sequence. Such inhibition is specific of the platelet fibrinogen receptor, the glycoprotein IIb-IIIa complex. Fragments containing the fibrinogen D domain were the only plasmin degradation products of fibrinogen which were mitogenic. These fragments acted via direct binding on the mitogenic receptor with a Kd of 2.24 X 10(-6) M. This value was similar to the KI value of unlabeled fragments D (2.47 X 10(-6) M). Our results suggest the presence of two different functional types of fibrinogen receptors: the glycoprotein IIb-IIIa receptor responsible both for platelet aggregation and leukocyte adhesion and killing, and the mitogenic receptor involved in proliferation control of hemopoietic cells.

A solid-phase fibrin immunoassay for the specific detection of monoclonal antibodies against different epitopic determinants of tissue-plasminogen activators

The selective detection of hybridomas producing monoclonal antibodies against tissue-plasminogen activators (t-PA) by means of a solid-phase fibrin immunoassay (SOFIA) is described. The screening method is based on the specific and high affinity binding of t-PA for fibrin solid phase. This, as in the physiological fibrin-t-PA interaction, provides a molecular structure conserving its antigenic and functional properties. The solid-fibrin-state support is prepared by thrombin proteolysis of fibrinogen coupled to a poly-glutaraldehyde activated polyvinylchloride plate. This procedure avoids fibrinogen desorption and provides a uniform fibrin network onto which t-PA from crude extracts or purified preparations, can be specifically absorbed. The fibrin-t-PA solid-phase support is able to fix anti-t-PA antibodies which can be subsequently revealed by a second enzyme- or radiolabelled anti-mouse Ig antibody. The results demonstrate the effectiveness of the SOFIA method for the selection of hybridomas producing anti-t-PA antibodies against different epitopic determinants of t-PAs.

Monoclonal antibodies to factor IX: characterization and use in immunoassays for factor IX

Monoclonal antibodies to factor IX have been characterized for potential use in purification of factor IX and for analysis of factor IX abnormalities seen in hemophilia B and other conditions. The properties of six monoclonal antibodies to factor IX are summarized in this report. Antibodies were selected for diverse reactions with factor IX and activated factor IX and which had been transferred to nitrocellulose. Two antibodies showed preference for the heavy chain of activated factor IX, one antibody showed preference for the intact factor IX molecule while three antibodies reacted with the heavy chain of activated factor IX and the intact factor IX molecule equally. Five monoclonal antibodies inhibited factor IX clotting activity. Two antibodies, most specific for factor IX by competitive binding assays, have proved to be useful in immunoassays for factor IX antigen in normal plasmas and in samples from hemophilia B patients.

An immunoassay for human D dimer using monoclonal antibodies

Monoclonal antibodies (MAb) were raised against human D dimer. The hybridomas were screened with a solid phase enzyme immunoassay against D dimer and fibrinogen degradation products. Among the panel of MAb identified, two distinct patterns emerged; the majority belonging to a panspecific class reacting against epitopes present on both D dimer and fibrinogen degradation product Dcate and a monospecific class reacting with determinants apparently present only on D dimer. A number of MAb were further characterised for their ability to specifically capture antigen in a solid phase enzyme immunoassay and assays were developed which have a sensitivity of 10 ng/ml for D dimer or crosslinked fibrin derivatives and may be suitable for detection of crosslinked derivatives in serum and plasma samples in a clinical situation.

Structural and genetic analyses of HLA class I molecules using monoclonal xenoantibodies

The monoclonal antibodies B1.23.2 and B9.12 were developed to characterize human class I major histocompatibility gene products. They detect two different epitopes and define on a given lymphoblastoid B cell line two subsets of beta 2 microglobulin-complexed HLA class I molecules. One subset reacts with B9.12 and B1.23.2 and the other one expresses only the B9.12 epitope. Binding assays were performed on C3H mouse L cells which had been transformed with various single HLA-class I genes and the two detected molecular subsets were shown to be encoded by different genetic loci. Unlike B1.23.2, B9.12 detects all the beta 2m-complexed molecules expressed in human B cell lines and recognizes an epitope different from the one defined by W6/32. In contrast to the vast majority of the other reported anti-class I monoclonal antibodies (including B9.12), B1.23.2 recognizes an epitope expressed on both beta 2m-associated and -free HLA class I heavy chains.