[The use of CEA radioimmunoassay for the detection of recurrence of carcinoma of the large bowel (author's transl)]. / 28. Der Radioimmunoassay zur Ermittlung des carcinoembryonalen Antigens (CEA), seine Bedeutung und Limitierung während der postoperativen Kontrollperiode von Patienten mit colorectalem Carcinom

Carcinoembryonic antigen (CEA) is a tumor marker defined by specific heterologous antisera. Elevated levels of circulating CEA can be detected by radioimmunoassay in most cases of colorectal carcinoma, depending on the degree of tumor spread. The fact that elevation of CEA level can also be observed in other types of carcinomas and in several nonmalignant conditions greatly limits the value of the CEA test for the early diagnosis of colorectal carcinomas. Repeated CEA measurements and their critical interpretation, however, appear to be of importance after tumor resection for the detection of tumor recurrence during the postoperative follow-up period.

[The influence of plasmocellular tumours on the humoral immune response in mice (author's transl)]. / Influence de deux tumeurs plasmocytaires sur la réponse immunitaire humorale de la souris

Syngeneic mice of the C3H/He strain have been inoculated with cells of the plasmocellular tumours X5563 and X5647, producing myeloma proteins of the IgG and IgA class respectively, and were immunized with (1) sheep red blood cells, (2) bovine serum albumin and (3) horseradish peroxydase. The immune responses of the various groups of mice were followed. The antibody activities towards all three antigens were decreased in mice carrying the IgG producing tumour X5563. This effect was correlated with an enhanced catabolism of IgG as well as with a decrease in number of IgG antibody producing cells. A reduced immune response was also observed in mice to which the IgA producing tumour X5647 had been transferred, but the effect was significantly less pronounced. There was no effect at all observed on the IgM response. The avidity which was measured for the various IgG antibodies was not modified by the presence of IgG nor IgA secreting myeloma tumours.

[Assay of the activity of horseradish peroxidase antibodies using ammonium sulfate technique (author's transl)]. / Dosage de l'activité des anticorps anti-peroxydase de raifort par la méthode au sulfate d'ammonium

The antigen binding capacity (ABC) of mouse and rabbit antisera to horseradish peroxidase (HRP) was measured by the Farr technique, originally introduced for bovine serum albumin. Results obtained by this method are independent of other antibody interactions (precipitation, formation of immune complexes, effect on enzyme activity). Commercially available HRP has variable solubility in ammonium sulfate solutions; almost 40% was precipitated at 50% saturation. Accordingly, the fraction of HRP soluble at 60% saturation was used, and this was labelled with 125I2 using the HRP oxidizing activity. Under these test conditions, accurate and reproducible results were obtained with protein concentrations (as N/ml) of the order to 0.07 mug (antibody) and 0.01 mug (antigen) respectively. This high sensitivity is superior to that achieved by passive hemagglutination, especially when titrating antibody levels in mouse sera.