title: Co-clustering activating and inhibitory receptors: impact at varying expression levels of the latter.
abstract: Clustering the mast cell function-associated antigen (MAFA) has earlier been shown to inhibit mast cells' secretory response to the type 1 Fcepsilon receptor (FcepsilonRI) stimulus. MAFA is a type II membrane glycoprotein first identified on rat mast cells and contains an immunoreceptor tyrosine-based inhibitory motif (ITIM) in its cytosolic domain. This inhibition is induced already upon clustering MAFA alone. Still, the inhibitory capacity of MAFA-FcepsilonRI co-clustering has recently been characterized and co-clustered MAFA molecules were found to exhibit a markedly higher inhibition capacity than MAFA-clusters alone. We have now compared the inhibitory capacity of FcepsilonRI co-clustered MAFA on the secretory response of rat mucosal-type mast cells (RBL-2H3 line) expressing different levels of this inhibitory protein. Reacting these cells carrying an IgE class, 2,4 dinitrophenyl (DNP)-specific monoclonal antibody with DNP-conjugated F(ab')2 fragments of non-specific polyclonal mouse IgG causes clustering of the FcepsilonRI-IgE. Reaction of these cells with DNP-conjugated F(ab')2 fragments of the MAFA-specific, monoclonal antibody G63 co-aggregates MAFA together with the FcepsilonRI-IgE thereby producing FcepsilonRI-IgE-MAFA co-clusters. Results of measurements of the secretory responses of RBL-2H3 cells expressing higher or lower MAFA levels than those of unmodified cells provided further support to the notion that co-clustered MAFA molecules exhibit a markedly higher inhibition capacity than MAFA-clusters alone. The molecular basis for this enhanced inhibition is most probably the increased concentration of the inhibitory cell components in the immediate proximity of the co-clustered FcepsilonRI-MAFA.
authors.affiliation: Department of Immunology, The Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Arieh
authors.initials: A
authors.lastname: Licht
authors.forename: Jakub
authors.initials: J
authors.lastname: Abramson
authors.forename: Israel
authors.initials: I
authors.lastname: Pecht
mesh_terms: D019297:2,4-Dinitrophenol / Q000276:immunology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D007073:Immunoglobulin E / Q000378:metabolism / Q000494:pharmacology; D007140:Immunoglobulin Fab Fragments / Q000494:pharmacology; D007074:Immunoglobulin G / Q000494:pharmacology; D037181:Lectins, C-Type / Q000378:metabolism*; D008407:Mast Cells / Q000187:drug effects / Q000276:immunology*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D009092:Mucous Membrane / Q000166:cytology / Q000187:drug effects; D051381:Rats; D017455:Receptors, IgE / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; C094696:Klrg1 protein, rat; D037181:Lectins, C-Type; D008562:Membrane Glycoproteins; D017455:Receptors, IgE; D007073:Immunoglobulin E; D019297:2,4-Dinitrophenol