Chemosensory G protein-coupled receptors (GPCR) in blood leukocytes

Chemosensory taste and smell perceptions are induced by adequate stimuli from our chemical environment interacting with their ca. 400 different odorant receptor types or 25 bitter taste receptor types, and sweet and umami receptor dimmers in the sensory cells of the olfactory or gustatory epithelia, respectively. Beyond an expression in their canonical chemosensory epithelia, there is increasing evidence for an ectopic expression of at least some 90 olfactory and taste G protein-coupled receptors in a variety of non-chemosensory epithelia and cells, including our cellular immune system. Here we review the evidence for the expression of chemosensory receptors in different types of blood cells, and discuss their putative immunological functions and roles as targets for receptor- and immune cell-specific bioactives, such as foodborne flavor chemicals, or allelochemicals in general.