5-HT2B Receptor on Macrophages: What for?

Macrophages can acquire a plethora of effector functions in response to the surrounding cytokines and tissue environment. Depending on their ontogeny and the prevailing extracellular stimuli, macrophages become specialized (“polarized”) for pathogen elimination and immune response promotion, or for tissue repair, wound healing and immunosuppression. This “polarization” versatility underlies the macrophage ability to maintain tissue homeostasis, as well as to initiate and resolve inflammatory responses. Recent findings indicate that macrophage functional polarization can be modulated through engagement of serotonin (5-HT) receptors on the macrophage cell surface. In the present chapter, we summarize the current knowledge on the physio-pathological relevance of the expression of serotonin receptor 5-HT2B on macrophages and other myeloid cells, and discuss its value as a functionally-relevant polarization marker and a potential therapeutic target in inflammatory responses.