Evolutionary constraints on CD1 structure: insights from comparative genomic analysis

It is well established that the CD1 family of proteins present lipid antigens to T cells. However, in vivo studies of CD1 function have been carried out almost exclusively using mouse models, despite the fact that mice lack most of the CD1 genes that are found in humans and other mammals. To understand why there is a difference in the number of CD1 genes observed between humans and mice, we used comparative genomic analysis to examine differences at the CD1 locus. This analysis reveals a significant genomic deletion in mice that provides a probable explanation for the disparity. Furthermore, we propose a hypothesis in which functionally convergent evolution could have a role in at least partially compensating for the loss of certain CD1 isoforms during the course of mammalian evolution.