Mutant EWI-2 fails to alter exposure of M38 epitope. (A) K562 cells transfected with α4 integrin (KA4; left) and KA4–EWI-2 (right) cells were analyzed by flow cytometry with anti-CD81 mAbs JS64 (gray histogram) and M38 (bold histogram). The open histogram shows staining with a negative control mAb. Cell-surface expression of α4β1 integrin was identical in both transfected cell lines (not shown). (B) MOLT-4 cells were analyzed as for panel A. The M38/JS64 ratio from 2 independent experiments is shown for control cells (white bars), EWI-2 (light gray bars), and EWI-2/cCD2 (dark gray bars) transfectants.