FIG. 2.

Profiles of the ampho-MLV envelope in the supernatant of cells. Indirect immunofluorescence flow cytometry patterns on CEAR13 cells expressing the amphotropic receptor PIT-2 and CERD9 cells which do not express it are shown. Supernatants are those of 4070A (ampho-MLV strain 4070A envelope; positive control) and D17.2G (ATCC), DSH134G, and D17 cells. The white profiles indicate cells stained by propidium iodide alone. The black profiles shows cells incubated with monoclonal antibody 83A25 against the ampho-MLV envelope (20). Only 4070A gave a strong positive signal. Two independent analysis were performed which yielded similar results.