The magnetoresistance (MR) effect between two antiferromagnetic layers separated by a nonmagnetic Cu layer was investigated. The MR ratio of 0.5% was observed in the structure of IrMn(8)/Cu(2.8)/IrMn(0.5)/CoFe(8) (in nanometers), where IrMn stands for Ir22Mn78 and CoFe for Co90Fe10. The study of different structures with and without top IrMn layer indicates that the MR effect originates from the giant magnetoresistance effect between the uncompensated magnetic moments at the IrMn interfaces across nonmagnetic Cu spacer.