Figure 1.

Inhibition of BCR-induced Ca²⁺ mobilization by coligation with PIR molecules. Mouse splenic B cells loaded with INDO-1 dye were analyzed by flow cytometry for intracellular Ca²⁺ levels in the presence (A) or absence (B) of extracellular Ca²⁺. Cells were stimulated with biotinylated F(ab′)₂ fragments of anti-μ and anti-PIR mAbs either alone or in combination as indicated by arrows. Biotin (10 μg) was used as a cross-linker. Independent ligation with the anti-PIR mAb had no inhibitory effect on the anti-μ induced Ca²⁺ response (not shown).