This paper presents an iterative receiver for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems over time-variant wireless channels. The receiver performs joint decoding, channel estimation, and multiuser detection, with soft information iteratively provided by the single-user decoders. Time-variance is effectively taken into account exploiting the properties of the discrete prolate spheroidal (DPS) sequences, being the bandlimited sequences with maximum energy concentration in time. Turbo codes are used for each transmit antenna, thus the receiver presents an iterative structure also in the single-user case. Simulation results for the performance are presented in terms of bit error rate (BER) and normalized mean square error (NMSE) vs signal-to-noise ratio (SNR). The effects of the number of external and internal iterations as well as the number of pilots on the performance of the system are investigated.