(Left) The eight exons of the HLA-G gene are arranged in the same sequence as other HLA class I genes. Unlike the other HLA class I genes, the HLA-G gene is alternatively spliced to yield seven transcripts. (Right) Four messages encode membrane isoforms (HLA-G1, HLA-G2, HLA-G3, and HLA-G4), and two encode soluble isoforms (HLA-G5 and HLA-G6, also known as sG1 and sG2, respectively). A stop sequence in intron 4 results in HLA-G5 and HLA-G6, and a stop codon in intron 2 results in a third, HLA-G7. HLA-G1 and HLA-G5 produced in some but not in all types of cells associate with light chain, β2m, whereas other isoforms do not.