If the protein you aim to detect in Western blot, following immunoprecipitation with an antibody, has a molecular weight of ~50 kDa, an anti-Rabbit light chain-specific antibody should be used.
If the protein of interest is ~25 kDa, an anti-rabbit IgG Fc specific antibody shoule be used, such as: Goat anti-Rabbit IgG Fc, HRP conjugated, min. cross-reactivity to bovine horse or human serum proteins.
Good luck with your research!