Binding of antibody to the gamma subunit of FCepsilonRI in rat basophilic leukemia cells results in morphological changes without inducing histamine release.
The high affinity IgE receptor on mast cells and basophils is composed of 3 subunits, alpha, beta and gamma. A polyclonal antibody was raised in rabbits to a 13 amino acid synthetic peptide corresponding to the amino terminal portion of the gamma subunit. The antiserum was screened using Western blots of solubilized RBL-2H3 cells and 125I goat anti-rabbit IgG. After purification of the serum on a protein G column, RBL-2H3 cells, mouse mast cells, and human basophils showed a doublet at 20 000 kDa. When 125I labeled, saponin-permeabilized cells were immunoprecipitated with the anti-gamma antibody, all 3 subunits of the IgE receptor complex coprecipitated. Furthermore, binding of the antibody to the cell surface did not induce histamine release. By immunofluorescence of fixed cells, the receptor was evenly distributed in the RBL-2H3 cells. Although no capping was observed when the cells were incubated with the antibody prior to fixation, the antibody did stimulate endocytosis when it was bound to the cells at 25 degrees C or at 37 degrees C, but not at 4 degrees C. Binding of the antibody to the RBL-2H3 cells also induced cell spreading and ruffling of the plasma membrane. The results of this study indicate that the gamma subunit of the high affinity IgE receptor may play a role in signal transduction.
Jamur
M C
MC
Departmento de Biologia Celular, Universidade Federal do Parana, Curitiba, Parana, Brasil.
Oliver
C
C
D000818:Animals; D000906:Antibodies / Q000737:chemistry / Q000494:pharmacology; D001491:Basophils / Q000737:chemistry* / Q000378:metabolism; D001666:Binding Sites, Antibody; D000939:Epitopes / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006636:Histamine Release / Q000276:immunology; D015471:Leukemia, Basophilic, Acute / Q000473:pathology*; D008854:Microscopy, Electron; D051381:Rats; D017455:Receptors, IgE / Q000737:chemistry / Q000276:immunology*; D014407:Tumor Cells, Cultured
D000906:Antibodies; D000939:Epitopes; D017455:Receptors, IgE