B3SAO and B3EQ bind BRIC 6 and interact with GPA.

When K562 clones were screened for B3SAO and B3EQ expression, both types of cells reacted with the murine monoclonal antibody BRIC 6. This was unexpected for K562/B3SAO cells; previous workers reported that BRIC 6 precipitates B3 but not B3SAO from Xenopusoocytes11 and that the binding of BRIC 6 to heterozygous SAO erythrocytes is reduced to 54% of normal levels.14Our flow cytometric analysis also showed that K562/B3SAO cells and K562/B3EQ cells bound all other antibodies that reacted with K562/B3 cells. The expression of both known epitopes within the Wr^bantigen on K562/B3SAO cells, detected by BRIC 14 and BRIC 201 binding, revealed that the abnormal B3SAO protein was still able to interact with GPA at the cell surface.