The flatworm Platyhelminthes is found at the stem position in the evolution of other metazoan animals, including other parasitic flatworms and their vertebrate hosts. Pathogenic immunomodulatory proteins are actually shared molecular keepsakes. In all probability, molecular mimicry is also the result of convergent evolution through extensive historical interaction between microbe and host. Not surprisingly, distinguishing between conservation and convergence is difficult. The horizontal transfer of DNA between pathogen and host has also been identified as a source of immunomodulatory proteins.
Retroviruses are the probable agents of such gene capture.
Second, identification of microbial immunomodulatory proteins occasionally precedes identification of its host counterpart, offering opportunities to discover new immunity-associated molecules and to further our understanding of the immune response. Lastly, the function and sites of activity of immunomodulatory proteins suggest potential agents of and targets for immunotherapy, respectively.