Hartmut Franz

Carbohydrate specificity of the receptor sites of mistletoe toxic lectin-I

Abstract The carbohydrate specificity of mistletoe toxic lectin-I (ML-I) was studied by haemagglutination-inhibition assay. The results indicated that ML-I has a broad range of affinity for Gal, α, β linked sequences. The galabiose (C, Gal α 1→4Gal) sequence, a receptor of the uropathogenic E. coli ligand, was one of the best disaccharide inhibitors tested. The lectin also exhibits affinity for Lac(Gal β 1→4Glc), T(Gal β 1→3GalNAc), I / II (Gal β 1→3/4GlcNAc) and B(Gal α 1→3Gal) sequences. Gal α 1→4Gal and Gal β 1→4Glc are frequently occurring sequences of many glycosphingolipids located at the mammalian cell membranes, such as intestinal and red blood cell membranes, for ligand binding and toxin attachment. This finding provides important information concerning the possible mechanism of intoxication of cells by the mistletoe preparation.

The in vitro activity of lectin I from mistletoe (ML I) and its isolated A and B chains on functions ofmacrophages and polymorphonuclear cells

We investigated the effects of ML I and its isolated chains, A and B, in regard to selected functions of phagocytes (human granulocytes, paraffin-oil stimulated M phi from guinea pigs). On these cells, ML I has no cytotoxic effect between 10(-14) and 10(-8) (trypan blue exclusion and ethidium bromide exclusion). Over the same concentration range, ML I and B chain diminish the negative surface charge of M phi and agglutinate M phi at concentrations greater than or equal to 2 X 10(-8) M (ML I) and greater than or equal to 3 X 10(-7) M (B chain), respectively. The diminishing of the negative surface charge shows two peaks, indicating the existence of two types of receptors on the M phi surface with different affinities for sugar-binding sites. Moreover, the B chain shows a third peak at higher concentrations (3 X 10(-8) M) that could be inhibited by D-galactose (greater than or equal to 10(-4) M). In comparison, the A chain reduces the surface charge at concentrations over 3 X 10(-7) M, but D-galactose has no effect on this. By means of the agarose droplet test, the spontaneous migration of M phi is inhibited in the sequence ML I much greater than B chain greater than A chain. The phagocytic activity of human leukocytes tested with a radiometric phagocytosis technique reveals an increasing effect only for the B chain; ML I and the A chain have no effect. Perhaps the mechanism of the described activities of ML I and its B chain are comparable with the action of lymphokines activating M phi.

Lectins — definition and classification

Summary 1. Present definitions of a lectin are critically compared. 2. In order to classify lectins the term “affinitin” was proposed. 3. Lectin-lectin conjugates may be useful tools.

Isolation and characterization of a lectin from garden cress (Lepidium sativum)

Summary A lectin has been isolated from extracts of garden cress ( Lepidium sativum ) by affinity chromatography on human immunoglobulin-Sepharose. The lectin reacts with human erythrocytes without specificity for the A, B and 0 blood group. Erythrocytes of animal origin are also agglutinated by the lectin. The hemagglutinating activity is abolished by heating the lectin solution at 70 °C or by dialysis against strong acid buffers. The hemagglutination reaction is not inhibited by monosaccharides. Lectin-glycoprotein interactions are described and discussed.

Anionic sites in the myelin sheath as shown by cationized ferritin

The distribution of anionic sites in the myelin sheath of sciatic nerves of rabbits was studied using cationized ferritin. Ferritin molecules were observed on the cytoplasmic sides of the myelin lamellae stratified in paranodes and Schmidt-Lanterman clefts. In the compact myelin, ferritin molecules have not been found in the tissue sections. They have been observed on membranes of the myelin fraction. The significance of the localization of negatively charged groups on the cytoplasmic side of membranes is discussed.

Heavy metal carbohydrate complexes for demonstration of lectin surface receptors the preparation of a galactan-iron complex

The preparation of a galactan-iron complex is described. The galactan iron complex can be used for electron microscopic demonstration of membrane bound Ricinus communis lectin because the high reactivity of this lectin toward the galactan.

Interaction of mistletoe lectin I with Kupffer cells and endothelial cells of mouse liver

The in vitro-formation of blebs by endothelial and Kupffer cells of the mouse liver after treatment with the toxic lectin I from mistletoe are demonstrated by means of scanning electron microscopy. The interaction of toxic lectins with nonparenchymal liver cells can be of importance concerning the elimination of these lectins in vivo.

Estimation of toxicity of the mistletoe lectin 1 using the footpad swelling test in mice

Summary Mistletoe lectin 1 (ML 1) causes footpad swelling (FPS) at a dose ≥ 0.025 μ g per mouse. Dose dependence and kinetics of the reaction have been measured.

Visualization of anionic sites using polyethyleneimine-metal complexes

17 Polyethyleneimine-metal complexes were synthesized and 3 of them were tested cytochemically for visualization of negative tissue charges. The demonstration of the anionic sites was carried out on rat cerebral cortex and on frog cutaneous pectoral muscle. As controls, neuraminidase digestion, methylation, and omission of osmium-postfixation were used. The osmiophilic properties of polyethyleneimine, polyethyleneimine salts, and polyethyleneimine-metal complexes were discussed.

Some properties of Con A-antibody conjugates

By application of antibody-Con A conjugates it is possible to perform a modified enzyme immunoassay. The reaction of an antigen with the corresponding antibody labelled by Can A results in a complex to which POD can be bound via the carbohydrate moiety of the enzyme. The enzyme can be quantified in the usual manner. A special advantage consists in the applicability of relatively impure POD preparations.