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Discovery of CD1 antigen presentation path-ways shows how T cells can specifically re-spond to self- and foreign lipid components of cells. Whereas most CD1 research focuses on CD1d and NKT cells, there are four types of CD1 antigen-presenting molecules, which are each broadly conserved in mammalian evolution (Kasmar et al., 2009). Recent data make clear that CD1a, CD1b, CD1c, and CD1d do not have redundant functions but instead have clearly differing patterns of tissue expression, distinctly shaped antigen binding grooves, diverse path-ways of intracellular trafficking, and trigger dif-fering effector functions of responding T cells (Young and Gapin, 2011). CD1c proteins are distinguished from other CD1 proteins by their constitutive expression at high density on the sur-face of marginal zone or activated B cells (Weller et al., 2004; Roura-Mir et al., 2005a; Allan et al., 2011) and subsets of DCs (Dzionek et al., 2000). Unlike CD1d, which is constitutively expressed on monocyte-derived DCs (MDDCs), CD1c is inducibly expressed on MDDCs after cytokine exposure (Porcelli et al., 1989; Yakimchuk et al., 2011). Thus, CD1c proteins have been proposed to mediate interactions of T cells with B cells and DCs as two major populations of APCs. Despite extensive knowledge of CD1c pro-tein trafficking in cells, the antigen-presenting function and antigens for the CD1c system are poorly understood. After translation, CD1