Group I is composed by CD1a, CD1b, and CD1c isoforms, group II by CD1d, and group III by CD1e.
CD1a is also expressed on Langerhans cells and CD1c in a subset of B cells .
Similarly to CD1a, CD1c has an F' pocket that is permissive to lipopeptide binding and usually associates with antigens that only have one alkyl chain, suggesting that the A' pocket might be occupied by spacer lipids that stabilize CD1c structure .
CD1a and CD1c localize in the endocytic recycling compartment, which indicates that they follow the slow recycling pathway back to the plasma membrane.
Evidence from crystallographic studies also suggests the presence of spacer lipids in CD1a, CD1c, and CD1d [19, 66, 69].
Importantly, CD1e promotes the loading and unloading of lipids into CD1d  and also influences lipid presentation by CD1b and CD1c .
Although CD1c is widely expressed in DCs and B cells from peripheral blood, only sulfatide and mLPA were identified as self-antigens presented by CD1c (Table 1) [14, 59].