IREM-1 (immune receptor expressed by myeloid cell 1) is a type I single transmembrane protein encoded by human chromosome 17q24.25. A member of the CD300 (CMRF-35) family and the Ig superfamily, IREM-1 is also known as CD300F, or CD300LF (CD300-like member F). CD300F is expressed on monocytes, granulocytes, and myeloid leukemia cell lines. The cytoplasmic domain of IREM-1 contains an ITIM and associates with the P85alpha subunit of PI3K (phosphoinositide 3-kinase). IREM-1 also functions as an inhibitory receptor.