Fine tuning by human CD1e of lipid-specific immune responses.

CD1e is a member of the CD1 family that participates in lipid antigen presentation without interacting with the T-cell receptor. It binds lipids in lysosomes and facilitates processing of complex glycolipids, thus promoting editing of lipid antigens. We find that CD1e may positively or negatively affect lipid presentation by CD1b, CD1c, and CD1d. This effect is caused by the capacity of CD1e to facilitate rapid formation of CD1-lipid complexes, as shown for CD1d, and also to accelerate their turnover. Similar results were obtained with antigen-presenting cells from CD1e transgenic mice in which lipid complexes are assembled more efficiently and show faster turnover than in WT antigen-presenting cells. These effects maximize and temporally narrow CD1-restricted responses, as shown by reactivity to Sphingomonas paucimobilis-derived lipid antigens. CD1e is therefore an important modulator of both group 1 and group 2 CD1-restricted responses influencing the lipid antigen availability as well as the generation and persistence of CD1-lipid complexes.