Tibor Borsos

Molecular basis of complement action

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Complement fixation on cell surfaces by 19S and 7S antibodies.

The mechanism of complement fixation on cell surfaces by whole antiserums, and by 19S and 7S fractions has been studied with a new comple-ment-fixation test. This test is based on the fixation and transfer of the activated first component of complement (Ć1a). We have concluded that a single molecule of 19S antibody in combination with antigen at the cell surface is sufficient to bind one molecule of Ć1a. For 7S antibodies at least two molecules in close proximity at the cell surface are required to fix one molecule of Ć1a.

125I protein A: applications to the quantitative determination of fluid phase and cell-bound IgG.

An improved method for the preparation of 125I-labelled Protein A (125I PA) of high specific and functional activity is described. 125I PA has been used in combination with purified rabbit IgG bound to a solid support to develop a competitive binding assay capable of detecting Protein A or human, rabbit and guinea pig IgG at the nanogram level. An optimal set of assay conditions was established and levels of IgG measured in normal human, rabbit and strain-2 guinea pig serum. 125I PA has also been used to detect IgG anti-Forssman antibody bound to sheep erythrocytes and to line-1 and line-10 tumor cells and as an indirect assay for tumor associated antigen in the ascitic fluid of tumor-bearing guinea pigs.

Neutralization of sensitized virus by the fourth component of complement.

Herpes simplex virus which had been sensitized with IgM antibody was not neutralized by the addition of the purified activated first component of complement. In the presence of an optimum concentration of the first component of complement, however, the sensitized virus was neutralized by the addition of a high concentration of the purified fourth component of complement. Under these conditions, the addition of the purified second and third components of complement failed to enhance virus neutralization. With low concentrations of the fourth component of complement, the addition of the second and third components enhanced virus neutralization.

Distinction between fixation of C1 and the activation of complement by natural IgM anti-hapten antibody: effect of cell surface hapten density.

Abstract Naturally occurring human IgM anti-methotrexate and anti-folinic acid antibodies were used to study the mechanism of complement (C)-mediated lysis of sheep red cells (E) labelled with methotrexate (MTX) or folinic acid (FA). We found that IgM bound to these cells in three forms: one binds C1 and activates the lytic sequence, the second binds C1 with no subsequent lysis, and the third neither binds C1 nor activates C. The ratio of the three forms depended on the density of hapten on the cell surface. It was concluded that the binding of one antigen-reactive site in the IgM to a cell surface hapten is not sufficient to activate the lytic sequence but may be sufficient to bind C1.

Titration of the first component of complement on a molecular basis: suitability of IgM and unsuitability of IgG hemolysins as sensitizer.

Abstract EAC4 prepared with rabbit IgM hemolysins are not suitable for c 1 and Cl titrations on a molecular basis. C 1 titrations with EAIgGC4 are insatisfactory because Cl transfers from site to site even at low ionic strength. Site to site transfer of C 1 during assay leads to an overestimation of C 1 activity. The use of EAIgGC4 for the assay of Cl leads to an underestimation of Cl activity. The latter difficulty is not due to a differential uptake of Cl by EAigGC4 and EAIgMC4 for we found that both cells take up Cl equally well, but the rate of activation of Cl to Cl is far greater on cells prepared with IgM.

A solid-phase immunoassay for human immunoglobulin E:Use of 125I-labeled protein A as the tracer

Abstract A solid-phase immunoassay has been developed for human immunoglobulin (Ig) E. The specific binding of 125 I-labeled protein A ( 125 I-PA) to the Fc region of rabbit IgG anti-IgE served as a quantitative measure of specific anti-IgE antibody bound to the IgE beads under optimal assay conditions. Inhibition of antibody binding by known amounts of standard IgE was reflected in a decreased binding of 125 I-PA. The degree of inhibition of 125 I-PA binding was related to the amount of fluid-phase IgE present and gave a standard curve which was used to determine the concentration of IgE in test samples. The sensitivity of this method and a double antibody radioimmunoassay (RIA), which was developed using the same IgE preparation and anti-IgE antibody, was approximately the same. These assays gave similar results when used to determine levels of IgE in normal human sera that had been absorbed with protein A—Sepharose to remove components responsible for specific and nonspecific interference in the assays.

Randomized clinical study on intratumoral BCG-cell wall preparation (CWP) therapy in patients with squamous cell carcinoma in the head and neck region

SummaryBased on animal experiments a clinical study with BCG cell wall preparation (CWP) was developed. Patients with head and neck carcinomas stage T1/2N0–2M0 were randomized. One group received surgical treatment only and a second group received preoperative intralesional BCG-CWP. So far 12 patients have been included in each group. After 3 years the CCR (complete cancer remission) in the surgery only group was 39% and that in the preoperative BCG-CWP group, 69% (P=11%). The cumulative proportion of surviving patients was 50% in the surgery only and 73% in the BCG-CWP group (P=21%). BCG-CWP injection was followed by an increase in body temperature and a decrease in peripheral blood lymphocytes. No changes in liver, kidney, or other organ function could be observed after BCG-CWP therapy. Complications and severe secondary effects such as have been described for living BCG were not observed, and significant immunological changes have not been detected so far.

Immunotherapy of Cancer: An Experimental Model in Syngeneic Guinea Pigs

Successful treatment of a solid tumor was accomplished by repeated intradermal injection of living tumor cells.

Molecular Interactions of Cells with Antibody and Complement: Influence of Metabolic and Physical Properties of the Target on the Outcome of Humoral Immune Attack

The discovery of complement emerged from the observations of Buchner (1839a,b,c), Von Fodor (1886, 1887), and Nuttal (1888) that guinea pig serum had bacteriocidal activity. Bordet (1895) subsequently demonstrated that the bacteriocidal activity of serum required the cooperation of a thermostabile substance, antibody, and a thermolabile substance, complement (C). Since then it has been shown that C is capable of interacting with and killing protozoa (Anziano et al., 1972), viruses (Almeida et al.,1972), erythrocytes (Kabat and Mayer, 1961; Rapp and Borsos, 1970), and nucleated cells (Green et al., 1959b; Green and Goldberg, 1960; Humphrey and Dourmashkin, 1969). In addition, complement activity has been detected in the sera of many mammalian species as well as in sera of lower vertebrates (Bellow, 1977).