The interaction of IgG subclasses with solubilized Fc receptors of rat basophilic leukemia cells.
Rat basophilic leukemia (RBL) cells carry two surface glycoprotein molecules named R (or alpha) and H which, when detergent solubilized, bind to rat IgE-Sepharose. The same two molecules also bind to rat IgG-Sepharose but with a lower affinity. R is a component of the high affinity Fc receptor for IgE. In the present study the inhibition of the binding of R and H to rat IgG-Sepharose by various homologous and heterologous immunoglobulins was used to assess their relative affinities for the two receptor molecules. Ranking the rat immunoglobulins in order of their affinities for the R receptor yielded: IgE much greater than IgG2a greater than IgG1 greater than IgG2b; and for H: IgE greater than IgG2b greater than IgG1 greater than IgG2a. Rat IgG2c inhibited the binding of both R and H but a precise ranking could not be assigned. Conclusive evidence has been obtained for the Fc specificity of these interactions. The affinities of the mouse IgG subclass/R interactions can be ranked: IgG1 greater than IgG2a greater than IgG2b; and for the H receptor: IgG1 greater than IgG2b greater than IgG2a. All of the mouse proteins and other heterologous IgGs, such as those of sheep, goat, equine and rabbit origin, interacted considerably more strongly with H than with R. No interaction with mouse IgG3 could be detected under the conditions tested.
Kepron
M R
MR
MRC Group in Allergy Research, Department of Immunology, University of Manitoba, Winnipeg, Canada.
Bazin
H
H
Froese
A
A
D000818:Animals; D000943:Antigens, Differentiation / Q000276:immunology; D001491:Basophils / Q000276:immunology; D003429:Cross Reactions; D007074:Immunoglobulin G / Q000145:classification / Q000276:immunology*; D007942:Leukemia, Experimental / Q000276:immunology*; D051381:Rats; D011961:Receptors, Fc / Q000276:immunology*; D017455:Receptors, IgE
D000943:Antigens, Differentiation; D007074:Immunoglobulin G; D011961:Receptors, Fc; D017455:Receptors, IgE