Effect of Concanavalin A on phagocytosis by macrophages

Cytofluorometric study on lectin binding of isolated guinea pig keratinocytes

Lectin binding was cytofluorometrically measured on fractionated keratinocytes of guinea pig. Free keratinocytes were obtained by treatment of EDTA and trypsin. After the treatment, they were separated into 3 fractions by centrifugation on a continuous colloidal silica (Percoll) density gradient. Cells in each fraction were stained by biotinyl lectins and avidin-FITC, and fluorescence intensity was measured by cytofluorometry. Results obtained indicate that little cell surface glycoconjugate is lost during the preparation of free keratinocytes.

Lectin binding patterns in amphibian epidermis

A battery of 6 different horseradish peroxidase conjugated lectins has been employed for structural localization of glycoconjugates in amphibian epidermis. Lens culinaris (LCA) lectin stained the basal membrane and gave no significant reaction on the epidermal layers. Canavlia ensiformis (Con A) and Griffonia simplicifolia II (GS II) lectins bound the keratinocyte cytoplasm and the basal membrane as well. Ulex europaeus I (UEA I) lectin had only reactivity with flask cells. Griffonia simplifolia I (GS I) and Glycine max (SBA) lectins preferentially bound the cell membranes of keratinocytes, being the intensity of the staining gradually increasing from the stratum spinosum to the stratum granulosum. These results show that UEA I, GS I, and SBA are good markers to distinguish different cell types and the degree of keratinocytes differentiation.

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

Distribution of glycoconjugates in normal human skin using biotinyl lectins and avidin-horseradish peroxidase

Lectin binding patterns in normal human skin were studied using five different biotinyl lectins and avidin-horseradish peroxidase. The staining pattern was specific for each lectin. In the epidermis, peanut agglutinin (PNA) and soybean agglutinin (SBA) preferentially stained the cell membranes of keratinocytes in the spinous and granular cell layers, indicating changes in the saccharide residues during keratinocyte differentiation. In the secretory segment of an eccrine sweat gland, the superficial cells gave a strong granular staining with Ricinus communis agglutinin (RCA). Dolichos biflorus agglutinin (DBA) and SBA, on the other hand, strongly stained the basal cells. With these lectins, two types of cells in the secretory segment were clearly distinguished. These results show that (1) PNA and SBA binding sites increase during the course of keratinocyte differentiation, and (2) RCA, DBA, and SBA are good markers to distinguish two types of cells in the secretory segment of an eccrine sweat gland.

Differential lectin binding to cellular membranes in the epidermis of the newborn rat

Three fluorescein-labeled lectins have been shown to exhibit specificity for the surface of cells in different layers of the epidermis in the newborn rat. An isolectin from seeds of Bandeiraea simplicifolia with specificity for alpha-D-galactosyl end groups labeled the basal and lower spinous cells; a lectin from Ulex europaeus exhibiting specificity for alpha-L-fucosyl units outlines the surface of spinous cells, and a second lectin from B. simplicifolia, with specificity for N-acetyl-D-glucosamine, labels the cornified cells. Appropriate blocking experiments have confirmed the specific nature of the binding.

Effect of concanavalin A and its succinylated derivative on the oxidative metabolism of guinea pig peritoneal macrophages

The effect of concanavalin A and its succinylated derivative on the metabolic regulation of guinea pig peritoneal macrophages was observed. The binding of tetravalent concanavalin A to the surface glycoproteins of macrophages caused a marked increase in the rate of oxygen consumption due to the activation of the hexose monophosphate shunt. Divalent succinylated concanavalin A, also induced a similar change in the rate of oxygen metabolism. The metabolic change induced by these two types of lectin was reversibly inhibited by alpha-methyl-D-glucoside, a haptenic inhibitor of these lectins, and was temperature dependent (observed at above 15 degrees C). It is suggested that the binding of these lectins to the surface glycoproteins, and not their cross-linking into caps, is required for the activation of oxygen metabolism of macrophages, and that highly fluid state of the plasma membrane seems to be an essential requirement for the transduction of glycoprotein perturbation on the macrophage surface into cellular interior via transmembrane control mechanism.

Inhibition of epidermal cell migration by concanavalin A in skin wounds of the adult newt

Pigment cell migration was used as an indicator to study the effects of the plant lectin, concanavalin A (con A), on epidermal cell closure of skin wounds. Continuous immersion of wounded animals in 10-100 microng/ml of con A greatly slowed but did not stop epidermal cell migration. Thus, untreated animals closed wounds in 12 to 24 hours while some treated wounds were still open after three days. Removal from con A after 24 hours, allowed inhibited wounds to close faster than those left in con A. Brief (30-minute) immersion of wounded animals in con A, either before or after migration had begun, suppressed closure for four to eight hours, demonstrating that the affinity for con A persists as epidermal cells migrate. When the left forelimb of bilaterally wounded animals was immersed in con A, it caused suppression of migration only on the immersed side, indicating a local rather than systemic site of action. Mixture with its competing sugar, alpha methyl D mannoside, abolished the effects of con A. The mechanism by which this lectin suppresses epidermal cell migration is unknown but clearly involves binding of the molecule to glycoprotein or glycolipid receptors on the cell surface.