HLA-G polymorphisms: neutral evolution or novel function?

HLA-G is a non-classical class Ib gene with many unusual features. Because of its unique expression pattern, which is primarily limited to fetal cells at the maternal fetal interface, this gene has gained the attention of many investigators. In this paper we review some of the novel features of HLA-G, with particular reference to polymorphic variants in the gene, and discuss the implications of these features for the potential function and evolutionary history of HLA-G.