The type 2 immune response controls helminth infection and maintains tissue homeostasis but can lead to allergy and fibrosis when improperly controlled. We reveal the existence of local tissue-specific enhancers of type 2 mediated-macrophage activation. In the lung, surfactant protein A (SP-A) enhanced IL-4-dependent proliferation and activation of alveolar macrophages, accelerating parasite clearance and reducing pulmonary injury following infection with a lung-migrating helminth. In the peritoneal cavity and liver, C1q enhancement of type 2 macrophage activation was required for liver repair following bacterial infection, but resulted in tissue fibrosis following peritoneal dialysis. Both SP-A and C1q generated their effects on macrophages via the unconventional myosin18A that acts as a cell surface receptor. We conclude that the structurally related defense collagens SP-A and C1q are tissue-specific factors that act through myosin18A to license local type 2 responses with consequences for parasite control, tissue repair, and fibrosis.

Tissue repair and regeneration after damage is not completely understood, and current therapies to support this process are limited. The wound healing process is associated with cell migration and proliferation, extracellular matrix remodeling, angiogenesis and re-epithelialization. In normal conditions, a wound will lead to healing, resulting in reparation of the tissue. Several risk factors, chronic inflammation, and some diseases lead to a deficient wound closure, producing a scar that can finish with a pathological fibrosis. Mesenchymal stem/stromal cells (MSCs) are widely used for their regenerative capacity and their possible therapeutically potential. Derived products of MSCs, such as exosomes or extravesicles, have shown a therapeutic potential similar to MSCs, and these cell-free products may be interesting in clinics. MSCs or their derivative products have shown paracrine beneficial effects, regulating inflammation, modifying the fibroblast activation and production of collagen and promoting neovascularization and re-epithelialization. This review describes the effects of MSCs and their derived products in each step of the wound repair process. As well, it reviews the pre-clinical and clinical use of MSCs to benefit in skin wound healing in diabetic associated wounds and in pathophysiological fibrosis.