Figure 2.

Factors regulating fibroblast effector function. Barrier tissue fibroblasts sense danger and respond to cytokines, leading to activation and release of effector molecules. Danger signals may be microbe- or host-derived and detected using surface, cytosolic, or endosomal receptors (purple). While these receptors can broadly be divided into a group that recognizes nucleic acids and group that recognizes certain molecules composed of proteins, lipids, and/or sugars, each receptor has evolved to recognize a unique set of ligands. Host-derived soluble protein signals called cytokines activate surface receptors (orange). Importantly, this figure represents a synthesis of barrier tissue fibroblast activating signals; more research is needed to understand how fibroblast activation varies between different fibroblast populations. Additionally, more work is needed to identify negative regulators and understand how other signals like neuronal factors, lipid mediators, and hormones impact barrier tissue fibroblast effector function.