Figure 2.

CTLA-4, but not Env, is endocytosed from the surface of HIV-infected T cells. (A) An Ab against the CTLA-4 luminal domain was incubated with H9-CTLA-4-GFP cells in culture before fixation, permeabilization, and staining with a Cy3-conjugated second Ab (red). The anti-CTLA-4 Ab was internalized to the same granules as those containing CTLA-4-GFP at steady state (GFP, green). (B) Three days after infection by HIV-1 (multiplicity of infection, 0.5), H9-CTLA-4-GFP cells were incubated on ice with anti-gp120 Ab. Cells were then washed and gp120 Ab internalization was allowed at 37°C before fixation, permeabilization, and staining with a secondary Cy3-conjugated Ab (red). Although gp120 was detected at the cell surface in some of the HIV-infected cells, endocytosis of the anti-gp120 was not detected in any of the cells. [Bars = 10 μm.]