This study investigates immune-related proteins in the sea anemone Nematostella vectensis using immunoprecipitation followed by label-free quantitative proteomics. Specific antibodies against the immune-related protein RLRb were used to enrich interacting proteins. The proteomic profiles of specific versus control (IgG) immunoprecipitations were compared to identify proteins enriched in the RLRb-associated complexes.