The human genes for the alpha and gamma subunits of the mast cell receptor for immunoglobulin E are located on human chromosome band 1q23.

The receptor with high affinity for immunoglobulin E (Fc epsilon RI) is a key molecule in triggering the allergic reaction. It is a tetrameric complex of one alpha subunit, one beta subunit, and two disulfide-linked gamma subunits. This receptor is present exclusively on mast cells and basophils. Molecules identical to the gamma subunit of Fc epsilon RI also form a cell surface complex with other Fc receptors such as mouse Fc gamma RIIa in macrophages and most probably with human Fc gamma RIII (CD16) in natural killer (NK) cells. Here we show by in situ hybridization that the human genes for the alpha (FCER1A) and gamma subunits (FCER1G) of Fc epsilon RI and the gene for Fc gamma RIII (FCGR3, CD16) are located on human chromosome band 1q23.