The human B cell-associated antigen CD24 is a single chain sialoglycoprotein
Journal of Immunology (Baltimore, Md. : 1950)
|May 15, 1986
Summary
The CD24 antigen, a human B cell marker, was re-evaluated using improved immunoprecipitation. Previous findings of a three-chain complex were disproven, revealing CD24 as a single 42 kDa protein, not associated with Fc-gamma receptors.
Area of Science:
- Immunology
- Molecular Biology
- Biochemistry
Background:
- The CD24 antigen, a human B cell marker, was previously characterized as a three-chain glycoprotein complex.
- The standard radioimmuneprecipitation technique yielded a profile of 45, 55, and 65 kilodaltons for CD24.
Purpose of the Study:
- To re-evaluate the molecular composition of the CD24 antigen.
- To compare standard radioimmuneprecipitation with a direct conjugation method.
- To investigate potential relationships between CD24 and Fc-gamma receptors.
Main Methods:
- Comparison of two immunoprecipitation techniques: standard radioimmuneprecipitation and direct BA-1 conjugation to CNBr-Sepharose.
- Electrophoretic analysis under reducing and nonreducing conditions.
- Cross-adsorption analysis using BA-1-Sepharose and IgG-Sepharose.
Main Results:
- Direct BA-1 conjugation yielded a single CD24 band at 42 kilodaltons, differing from the previous three-chain profile.
- The 55 and 65 kilodalton components were identified as artifacts due to co-migration with IgM and IgG heavy chains, respectively.
- No evidence of a relationship between CD24 and the 45 kilodalton Fc-gamma receptor was found.
Conclusions:
- The CD24 antigen is a single 42 kDa glycoprotein, not a multi-chain complex.
- Previous characterizations of CD24 were influenced by co-precipitating immunoglobulin heavy chains.
- CD24 is distinct from the Fc-gamma receptor on B cells and eosinophils.
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