Immunity protein component of a toxin-immunity protein module, which functions as a cellular contact-dependent growth inhibition (CDI) system. CDI modules allow bacteria to communicate with and inhibit the growth of closely related neighboring bacteria in a contact-dependent fashion. Protects cells against the 16S rRNase activity of CdiA-CT, its cognate toxin protein, but not against the toxic effects of a similar rRNase, non-cognate CdiA-CT from E.chrysanthemi strain EC16. Interacts with cognate toxin fragment CdiA-CT. Not expressed under laboratory conditions.