Fig 1. Distinct microbial compositions may lead to different outcomes (hypothetical scenario).

Combinatorial effects of microbial effectors and the active host pathways determine the cell response. (a) Composition1 has certain microorganisms that secrete effector protein combination1. These effectors activate pathway1 in the host, which produces pro-inflammatory cytokines. (b) Composition2 secretes effector combination2 and activates pathway2 in addition to pathway1. Additive effects of these two pathways amplifies the signal and promotes inflammation (cross-activation). (c) Microbial composition3 utilize effector combination3 to activate both pathway 1 and 3, which have opposing outcomes. Subtractive effects of these pathways result in no inflammation (cross-inhibition).