  We study the off-equilibrium response and correlation functions and the
corresponding fluctuation-dissipation ratio for a purely dissipative relaxation
of an O(N) symmetric vector model (Model A) below its upper critical dimension.
The scaling behavior of these quantities is analyzed and the associated
universal functions are determined at first order in epsilon expansion in the
high-temperature phase and at criticality. A non trivial limit of the
fluctuation-dissipation ratio is found in the aging regime.
