(A) The domain structure of an integrin α (grey) / β (black) heterodimer is shown as indicated by refs 7, 8 and 9. The plasma membrane is depicted as a white rectangle. The βA domain contains the epitopes for a number of function modulating mAbs including 12G10 and TS2/16. In (B), (C) and (D) schematic representations of the α4/α5 chimeras expressed in K562 cells are shown in which the α4 subunit domains are grey and the α5 subunit domains are white. (B) Schematic of the chimera in which the α4 tail has been swapped for the α5 tail, (C) schematic of the α4Pα5L chimera which comprises the propeller domain of α4 (Y1-L440) and the α5 leg, transmembrane and cytoplasmic domains (T459-A1008), and (D) schematic of the X4C0 chimera (36) in which the α4 tail was truncated after the GFFKR motif.