Three murine monoclonal antibodies (MAbs) reactive to different epitopes on CEA were selected according to their ability to bind to various human tissue sections. The most selective MAb, BW 431/31, bound to the majority of colon carcinomas but only faintly to normal colon mucosa. In addition to the tissues stained by MAb BW 431/31, MAb BW 250/183 reacted with granulocytes, colon mucosa and faintly with pancreatic ducts. The third MAb, BW 374/14, reacted with granulocytes, colon mucosa, strongly with pancreatic ducts and with alveolar and bronchial epithelium. The antigenic determinants recognized by the 3 MAbs in human tissue sections were resistant to formaldehyde fixation and paraffin embedding as well as to periodic acid oxidation and neuraminidase treatment. The last two treatments suggest that the epitopes are protein in nature. Using MAb affinity chromatography, 3 antigen preparations were isolated from a human colon carcinoma xenograft with an approximate molecular weight of 180 kd. These preparations were shown to bear the epitopes from each of the MAbs and from a polyclonal antiserum specific for purified CEA. Furthermore, the ability of MAb BW 431/31 to localize its antigenic determinant in vivo on a human colon carcinoma xenograft is evaluated and its possible application in the patient is suggested.

Antamanide is the name we have given to a constituent of the fungus Amanita phalloides. This substance counteracts the lethal action of the Amanita toxins phalloidine and u-amanatine if administered to the white mouse before, or simultaneously with, the poisons. Its concentration in the fungus is, however, so low that the toxic action of the latter predominates. Antamanide is a cyclic decapeptide formed from the L-amino acids alanine, phenylalanine, proline, and valine in the molar ratio 1:4:4:f. The amino-acid sequence was determined by a combination of gas chromatography and mass spectrometry. The structural formula assigned was confirmed by synthesis according to a classic route of peptide chemistry.

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The murine monoclonal antibody (MAb) BW 494 was characterized in relation to its tissue specificity, the epitope recognized, in vitro and in vivo radiolocalization and its potential to mediate antibody dependent cellular cytotoxicity (ADCC) and complement mediated cytolysis (CMC). The MAb defined carbohydrate epitope located on a greater than 200 k daltons glycoprotein was mainly expressed on the majority of well differentiated adenocarcinomas of the pancreas. Furthermore, the epitope is accessible to MAb BW 494 in vivo, allowing an enrichment of radioactive antibody at the tumor site in nude mice. Additionally, MAb BW 494 is able to use human peripheral blood lymphocytes as effector cells for ADCC reactions against appropriate tumor target cells in vitro. In contrast, the antibody does not mediate human or rabbit CMC.

Starting from the phenomenon that the amount of circulating CEA in patients' sera did not significantly influence immunoscintigraphic visualization of CEA expressing tumors, we built up an in vitro model to explain this phenomenon. Blocking experiments in this model system showed that the CEA specific MAbs BW 431/26 and BW 431/31 could not be inhibited in their binding to cell associated CEA, if they were preincubated with a 20 molar excess of serum CEA. In contrast, the CEA-NCA cross reactive MAbs could be inhibited in their binding to tumor associated CEA under identical conditions. These data combined with western blotting analysis of patients' sera and affinity constant determinations argue that conformational changes in serum CEA cause a decreased affinity of the CEA specific MAbs to serum CEA allowing a preferential binding to tumor associated CEA.

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S-sulfonation represents a reversible chemical modification of disulfide bonds by which under the special conditions chosen only about 2.2 cystine units per IgG molecule are cleaved. Physicochemical and functional evidence for reconstitution is presented. Molecules reconstituted in vitro or in vivo regain, within a few hours, a reactivity (antigen binding, immunoprecipitation, Clq-mediated cross-linking of immune complexes) comparable to equimolar control preparations.

In December of last year the Nobel Prize for Medicine or Physiology was awarded to the natural scientists N . K . Jerne, C. Milstein, and G. Kohler. These three immunologists have contributed fundamentally to our understanding of antibody synthesis by the individual immune cell. They confirmed the rule, established in the sixties, that only one antibody comes from each type of immune cell, thus giving it the status of a dogma. Jerne worked out the basic understanding of the great variety of antibodies, and his Jerne-Plaque-Test (1963) has enabled us to describe and analyze a single antibody-producing immune cell in vitro. Thus, the study of immune cell interaction and the cooperation of lymphocyte subpopulations, which leads to the formation of antibodies, received decisive impulses and important methodological prerequisites. In 1975 Kohler and Milstein succeeded in permanently stabilizing, i.e., immortalizing, the antibody production of an already immunologically specifically primed mortal immune cell by means of cell fusion (hybridization) with an immortal, cancerous immune cell (myeloma cell). The hybrid cell and the hybrid cell clone grown from it in cell culture produced a homogeneous antibody, having the desired constant binding specificity, in a practically unlimited fashion and independently of an animal organism, a monoclonal antibody. This scientific breakthrough was the beginning of a tremendously stimulating new biotechnological development, which very quickly spread to laboratories in diverse fields and which today enables us to take up, and in part even solve, scientific, technical, and medical problems that would otherwise not have been analyzable at present.