  We present an analytical expression for the static many-body local field
factor $G_{-}(q)$ of a homogeneous two-dimensional electron gas, which
reproduces Diffusion Monte Carlo data and embodies the exact asymptotic
behaviors at both small and large wave number $q$. This allows us to also
provide a closed-form expression for the spin-antisymmetric exchange and
correlation kernel $K^{-}_{xc}(r)$ which represents a key input for
spin-density functional studies of inhomogeneous electronic systems.
