CD81 and acute myeloid leukemia: To determine whether MIF mediated the AML-promoting effects of CD81+ Erys, we pretreated CD81+ Erys with the MIF-specific inhibitor 4-iodo-6-phenylpyrimidine (4-IPP), which irreversibly inhibits the biological activity of MIF (33), and cocultured the 4-IPP–pretreated CD81+ Erys with AML cells.