Intracellular calcium mobilization was defective in the absence of homotypic 2B4/CD48 interaction. WT LAK cells generated in the absence or presence of a2B4 mAbs were loaded with Fura-2, and intracellular calcium concentration was monitored as described in “Materials and methods.” The calcium concentration was depicted as the emission ratio of 380:340 nm. RMA/S cells (2 × 106) were added at the time indicated, and 4 μM ionomycin was added at the end of the experiments to ensure that the cells are viable. (A) Thirteen of 20 cells in a field induced elevation of intracellular calcium and are presented in the figure. (B) Thirteen of 20 cells were depicted in the figure. None of the cells in a2B4-treated group showed elevation of intracellular calcium.
