Margarete Malter

Natural killer cells, vitamins, and other blood components of vegetarian and omnivorous men

The study population consisted of male vegetarians (aged 28-50 years), who were recruited from the vegetarian cohort being followed by the Department of Epidemiology (German Cancer Research Center, Heidelberg, FRG), and the same number of age- and sex-matched controls from the personnel of the same center. Among the vitamins tested, only the level of carotene was significantly higher in vegetarians; the levels of vitamin A, K, and E were not elevated. Among the other blood parameters tested, only creatinine and glutamine-transferase levels were significantly lower in vegetarians. The natural cytotoxicity of peripheral blood lymphocytes was measured using a chromium-release test. Cytotoxic activity, which is expressed as lytic units, was significantly higher in vegetarians than in their omnivorous controls by a factor of 2. The total number of white blood cells, lymphocytes, and other subpopulations did not differ between vegetarians and nonvegetarians. The enhanced natural cytotoxicity may be one of the factors contributing to the lower cancer risk shown by vegetarians.

Liver as a Tumor Cell Killing Organ

Lymphoma cells (Eb and ESb, the metastasizing variant) were injected via a mesenteric vein. 85% to 95% of these cells were trapped in the liver. Most of the Eb cells (81%) were destroyed within 18 hours, ESb cells prove to be more resistant: only 28% of these cells were destroyed within this time. 51-Chromium release assay (4 hours) revealed a similar sensitivity of these two tumor cell strains.

Natural cytotoxic cells from rat liver and spleen kill human glioma cells

SummaryNatural cytotoxic cells from rat spleen and rat liver, (isolated using the collagenase method) were found to be cytotoxic against different lines of human gliomas: T406, T508, T705, HeRo, HeRoCl 1, HeRoCl8, and HeRo-SV 7/114. After 18 h the lytic units ranged from 75 to 251 in the liver and from 5 to 24 in the spleen. Analyzing the ratio of lysis at 4 h/ 18 h, it may be concluded that this natural killing is predominantly macrophage (Kupffer cell)-dependent. Lysis by Kupffer cells cannot be increased by transforming glioma cells with SV40. Experiments with SV40-transformed mouse fibroblasts (3T3) and virustransformed human cell lines (SV80) suggested a “SV40” receptor on Kupffer cells. Thus Kupffer cells have receptors for glioma cells and SV40-dependent membrane structures.

Mechanismen der Krebsentstehung

Der Forschungsschwerpunkt „Mechanismen der Krebsentstehung“ befast sich mit der Grundfrage, wie und wodurch Krebs zustande kommt. Die darin zusammengefasten Forschungsvorhaben haben damit ein gemeinsames Konzept, das sich bei aller Verschiedenartigkeit der experimentellen Ansatze, folgendermasen beschreiben last: Modellhaftes Nachvollziehen der Umwandlung einer Normalzelle in eine Krebszelle unter bewust gewahlten Bedingungen, die eine moglichst luckenlose Beobachtung der zur Krebsentstehung fuhrenden molekularen Vorgange erlauben. Dabei ist das Experimentieren mit krebsauslosenden Strahlen, chemischen Karzinogenen sowie Tumorviren prinzipiell gleichwertig, ja, es ist sogar geboten, denn Krebs wird nicht durch eine einzige, sondern durch viele Ursachen hervorgerufen, und dieser Tatsache hat das Experiment Rechnung zu tragen.

Cytotoxic T-cells and antibody-producing cells isolated from liver and spleen of immunized rats.

SummaryLiver, strategically positioned within the circulation system, is a major trap for circulating tumor cells. Trapping and killing of tumor cells may be mediated by Kupffer cells und natural killer cells. In addition to these spontaneously cytotoxic cells, we isolated T-killer cells and antibody-producing cells from the liver after immunization with xenogeneic cells. Since tumor surveillance may include T-killer cells and antibody-dependent killer cells, the liver is able to attack tumor cells by “natural” and “induced” cytotoxic mechanisms.

Die wichtigsten Zahlen auf einen Blick

In der Welt gibt es im Augenblick uber 40000 AIDS-Falle, davon 29000 in den USA (Anfang Februar 1987), 840 in der Bundesrepublik.

Mechanisms of Carcinogenesis

The research focused on “mechanisms of carcinogenesis” is concerned with the fundamental question as to how and why cancer arises. The research projects grouped together here thus have a common concept. Despite all diversity of the experimental approaches, this concept can be described as follows: Model reconstruction of the transformation of a normal cell into a cancer cell under deliberately chosen conditions which allow as complete as possible an observation of the molecular processes leading to cancer development. Experimentation with cancer-inducing rays, chemical carcinogens as well as tumor viruses are in principle equivalent. It is indeed appropriate to experiment with different agents, since cancer is not caused by a single factor but by many causes, and this must be borne in mind in experimentation.