Confocal microscopy of cells labeled with anti–LDL receptor Ab. (a–f) EBV-lymphocytes were incubated with rabbit anti–LDL receptor (red) at 4°C, washed at 4°C, and either directly permeabilized (a–c) or incubated for 10 minutes at 37°C before permeabilization to allow internalization of LDL receptor/Ab complexes (d–f). Permeabilized cells were then incubated with mouse anti–α-adaptin (AP2), washed, and incubated with Alexa 568–conjugated goat anti-rabbit IgG (LDL receptors, red) and Alexa 488–conjugated goat anti-mouse IgG (AP2, green). Nuclei were stained with DAPI. The plates shown are an overlay of red and green images. The bar represents 5.0 μm. (a and d) Control cells; (b and e) cells from proband 1.1; (c and f) cells from proband 1.1 expressing viral c-myc-ARH. (g–l) EBV-lymphocytes (g–i) or cultured skin fibroblasts (j–l) from three different control subjects were incubated with anti–LDL receptor Ab at 4°C, permeabilized, and then incubated with anti–α-adaptin Ab (AP2) as described for a–f above. The bars represent 5.0 μm (in g for g–i, and in j for j–l).