title: Effect of concanavalin A dose, unbound concanavalin A, temperature, Ca2+ and Mg2+, and vinblastine on capping of concanavalin A receptors of human peripheral blood lymphocytes.
abstract: The capping of Concanavalin A (Con A) receptors induced by Con A was studied using human peripheral blood lymphocytes. The effects of Con A dose (5--100 micrograms/ml), pretreatment at 4 degrees C, unbound Con A, extracellular Ca2+ and Mg2+ and vinblastine were evaluated using Con A-horseradish peroxidase and electron microscopy. Lymphocytes incubated with Con A at 4 degrees C and fixed with glutaraldehyde exhibited Con A-horseradish peroxidase around the entire cell periphery. After raising the temperature to 37 degrees C, the Con A-horseradish peroxidase moved to form a cap at one pole of the cell and subsequently underwent endocytosis. Capping of Con A receptors induced by Con A at 37 degrees C was observed only at low Con A concentrations in the presence of unbound Con A and extracellular Ca2+ and Mg2+. Increased capping was found after pretreatment of cells with Con A at 4 degrees C, removing unbound Con A and/or removing extracellular Ca2+ and Mg2+, and by treatment with vinblastine. Following removal of both unbound Con A and extracellular Ca2+ and Mg2+, the percentage of capped cells at 37 degrees C was the same as on pretreatment at 4 degrees C under the same conditions. While pretreatment at 4 degrees C caused the breakdown of microtubules, removal of unbound Con A and/or extracellular Ca2+ and Mg2+ had no morphological effect on microtubules or microfilaments. Following exposure of lymphocytes to vinblastine and removal of unbound Con A, capping of Con A receptors by Con A was observed in over 90% of cells at all Con A dosages. However, when cells were exposed to vinblastine in the presence of unbound Con A the formation of Con A caps was either partially or completely inhibited.
mesh_terms: D002118:Calcium / Q000494:pharmacology; D003208:Concanavalin A / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007152:Immunologic Capping / Q000187:drug effects*; D066298:In Vitro Techniques; D008214:Lymphocytes / Q000276:immunology* / Q000648:ultrastructure; D008274:Magnesium / Q000494:pharmacology; D008854:Microscopy, Electron; D008870:Microtubules / Q000648:ultrastructure; D011952:Receptors, Concanavalin A / Q000276:immunology*; D011955:Receptors, Drug / Q000276:immunology*; D013696:Temperature; D014747:Vinblastine / Q000494:pharmacology
chemical_list: D011952:Receptors, Concanavalin A; D011955:Receptors, Drug; D003208:Concanavalin A; D014747:Vinblastine; D008274:Magnesium; D002118:Calcium