[en] We study relations between quantum sl(n) and quantum sl(k) when q^n+k = ± 1. We show that after restriction to type II representations, the commutant of U_qsl(n) in Y_nk^xL and the commutant of U_qsl(k) in ^tY_kn^xL (where Y is a Young tableau and ^tY its transpose with respect to NW-SE diagonal) are mapped into each other by R_nk → R_kn^-1. Applications to lattice integrable models and link polynomials are discussed. We show in particular that the link polynomials built from U_qsl(n), Y and U_qsl(k), ^tY take complex conjugate values when q^n+k = ± 1. (orig.)