Schrödinger's cytokine

Resident cytokines (released from cells in the body) are potent proteins that function at vanishingly low levels (measured in ng/kg). In contrast, therapeutic recombinant cytokines are typically dosed in mg/kg. Similarly, high mg/L concentrations are required for cytokines used in lab-based cell culture or in biomanufacturing. How do almost non-existent resident cytokines manage to achieve their effects?