CD1 antigen presentation: how it works.

The classic concept of self-non-self discrimination by the immune system focused on the recognition of fragments from proteins presented by classical MHC molecules. However, the discovery of MHC-class-I-like CD1 antigen-presentation molecules now explains how the immune system also recognizes the abundant and diverse universe of lipid-containing antigens. The CD1 molecules bind and present amphipathic lipid antigens for recognition by T-cell receptors. Here, we outline the recent advances in our understanding of how the processes of CD1 assembly, trafficking, lipid-antigen binding and T-cell activation are achieved and the new insights into how lipid antigens differentially elicit CD1-restricted innate and adaptive T-cell responses.