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We report calculations, based on the tight-binding model and the nonequilibrium Keldysh formalism, of the effect of band-filling (BF) asymmetry between the ferromagnetic leads on the bias behavior of the spin torque and the tunneling magnetoresistance (TMR) in magnetic tunnel junctions. The underlying mechanism for the asymmetry-induced change in the bias dependence of TMR and the spin-transfer component, , is the interplay of charge and spin currents in the ferromagnetic (FM) and antiferromagnetic (AF) configurations. The BF asymmetry has a dramatic effect on the low-bias behavior of the fieldlike component, , which can vary from linear to quadratic bias dependence with positive or negative curvature, thus reconciling the apparently contradictory experimental results. A general expression is derived relating with four independent nonequilibrium interlayer exchange couplings (NEIECs), , associated …