Although I may seem like a small distinction, I don't think it is.
A white blood cell may serve to protect the body from disease, but from a
cellular level all a white blood cell does is envelop other cells which
match certain profiles (tagged with certain chemical receptors). Its roll
in the larger structure is a niche it has adapted to. And that adaption is
relfected in its structure.
The same might be said of a meme within a meme-structure.
-Prof. Tim