FcRIExpression

FcRIExpression refers to the surface expression of FcεRI, the high-affinity IgE receptor, on immune cells. In humans, the most prominent sites are mast cells and basophils, where FcεRI is densely expressed and drives rapid allergic responses. Lower, but detectable, levels can also be found on dendritic cells, eosinophils, and some monocytes, particularly in atopic individuals.

FcεRI is a high-affinity receptor for IgE. On mast cells and basophils, the receptor is typically a tetramer composed of α, β, and γ2 chains; some cells can express a trimeric form lacking the β chain. The α chain binds IgE, while the β and γ chains participate in signal transduction that leads to degranulation and cytokine release when IgE bound to the receptor is crosslinked by antigen. The receptor’s density on the cell surface influences sensitivity to allergens.

Expression levels are regulated by immune signals and IgE exposure. Th2 cytokines such as IL-4 and IL-13 upregulate FcεRI transcription, particularly of the α subunit, increasing receptor density. The presence of circulating IgE stabilizes FcεRI on the surface, so higher IgE levels correlate with higher receptor expression. Conversely, therapies that lower IgE, such as anti-IgE antibodies (e.g., omalizumab), reduce FcεRI surface density on mast cells and basophils over weeks.

Clinical and research relevance includes a link between FcεRIExpression and allergic reactivity, with higher expression associated with atopy and asthma risk. Measurement is commonly performed by flow cytometry using anti-FcεRI antibodies, while mRNA levels can be assessed by RT-qPCR.