TAAR Immunopharmacology

Trace amine-associated receptors (TAARs) were originally identified as G protein-coupled receptors involved in monoaminergic signaling within the central nervous system. However, accumulating evidence indicates that TAARs, particularly TAAR1 and TAAR2, are also expressed in the immune system, including circulating leukocytes, lymphocytes, macrophages, and microglia. This chapter reviews current evidence regarding TAAR expression, functional pharmacology, and potential translational relevance within the immune system.Expression studies support a predominant TAAR1/TAAR2 pattern across both innate and adaptive immune-cell populations. Functional studies indicate that TAAR signaling can modulate inflammatory responses through chemotaxis, cytokine production, and immunoglobulin secretion. However, these effects are highly context-dependent, preventing a simple classification of TAAR signaling as either pro-inflammatory or anti-inflammatory.The chapter also discusses the emerging role of TAAR signaling in the pathophysiology of diseases, including inflammatory bowel disease, methamphetamine-associated immune dysfunction during HIV infection, multiple sclerosis, Parkinson's disease, fibromyalgia, and hematological malignancies.Despite growing interest in TAAR immunopharmacology, the current evidence remains largely preclinical and methodologically heterogeneous. Major limitations include incomplete protein-level validation, reliance on immortalized cell lines or mixed-cell populations, species-specific pharmacology of available ligands, and limited understanding of physiological trace amine signaling under basal conditions. Further integrative studies will be required to clarify TAAR pathophysiological significance and determine whether TAAR-targeted strategies may have translational relevance in immune-mediated disorders.