Activation of rat basophilic leukemia cells by epsilon BP, an IgE-binding endogenous lectin.
IgE-binding protein (epsilon BP) is a beta-galactoside-binding animal lectin identified by its affinity for IgE. We have reported that epsilon BP also binds the mast cell high-affinity IgE receptor (Fc epsilon RI), via lectin-carbohydrate interaction. We have now studied the physiological significance of epsilon BP-IgE-Fc epsilon RI interactions in mast cell activation using rat basophilic leukemia (RBL) cells as the model system. We report here that both unsensitized and IgE-sensitized RBL cells are activated upon exposure to epsilon BP-coated surfaces. Activation of RBL cells by the lectin epsilon BP can be significantly inhibited by appropriate saccharides. Exposure of RBL cells to epsilon BP-coated surfaces caused cell spreading similar to that caused from adherence to fibronectin-coated surfaces. However, epsilon BP by itself caused mediator release whereas fibronectin only potentiated antigen-mediated activation of RBL cells. Under appropriate conditions, epsilon BP, therefore, has the potential to activate mast cells culminating in augmentation of an inflammatory response.
Zuberi
R I
RI
Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, California 92037.
Frigeri
L G
LG
Liu
F T
FT
D000818:Animals; D000941:Antigens; D000943:Antigens, Differentiation / Q000737:chemistry / Q000494:pharmacology*; D002448:Cell Adhesion; D015550:Cell Degranulation / Q000187:drug effects; D037502:Galectin 3; D007073:Immunoglobulin E / Q000494:pharmacology; D066298:In Vitro Techniques; D037102:Lectins; D015471:Leukemia, Basophilic, Acute; D051381:Rats; D012701:Serotonin / Q000378:metabolism; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
D000941:Antigens; D000943:Antigens, Differentiation; D037502:Galectin 3; D037102:Lectins; D012701:Serotonin; D007073:Immunoglobulin E