Competitive coexistence in antiviral immunity.

Adaptive immunity to viruses in vertebrates is mediated by two distinct but complementary branches of the immune system: the cellular response, which eliminates infected cells, and the humoral response, which eliminates infectious virus. This leads to an interesting contest, since the two responses compete, albeit indirectly, for proliferative stimuli. How can a host mount a coordinated antiviral campaign? Here we show that competition may lead to a state of "competitive coexistence" in which, counterintuitively, each branch complements the other, with clinical benefit to the host. The principle is similar to free-market economics, in which firms compete, but the consumer benefits. Experimental evidence suggests this is a useful paradigm in antiviral immunity.