Cellular localization of GPIIb by immunofluorescence staining. (A) Transfected cells were stained simultaneously with SZ22 against GPIIb (green) and calnexin, an ER marker (red). The yellow color demonstrates colocalization of GPIIb with an organelle marker (merger of red and green). WT GPIIb is localized in the plasma membrane as well as the ER, whereas alt.25 and del.20 GPIIb are located only in the ER. (B) Transfected cells were stained simultaneously with SZ22 against GPIIb (green) and rabbit polyclonal antibodies against mannosidase II (red). Colocalization of GPIIb and mannosidase II, a Golgi marker, is seen in cells with WT GPIIb but not in cells harboring GPIIb alt.25 and del.20. Original magnification, × 1000.