Abstract Unlike the highly polymorphic, peptide-presenting conventional MHC molecules, CD1 consists of a family of monomorphic, lipid-presenting proteins. Recent studies have revealed the molecular basis of mycobacterial lipid recognition by CD1a-c-restricted T cells. In addition to foreign lipids, subsets of CD1a-c-restricted T cells recognize self-lipids, which may have implications for human diseases such as autoimmunity and cancer. And yet, the molecular identity of these self-reactive T cells remains largely elusive. In this study, using a novel CD1c+ artificial antigen-presenting cell (aAPC)-based system, we have isolated human CD1c-restricted autoreactive T cells and characterized them at the molecular level. By employing the human cell line K562, deficient in MHC class I/II and CD1 expression, as a backbone, we generated an aAPC expressing CD1c as the sole antigen-presenting molecule with costimulatory molecules, CD80 and CD83. When stimulated with this CD1c+ aAPC endogenously presenting self-lipids, a subpopulation of primary human CD4+ T cells from multiple donors consistently upregulated CD154 (CD40L) in a CD1c-specific manner. These activated CD4+ T cells preferentially expressed TRBV4-1+ TCRs. Interestingly, TRAV usage and CDR3 sequences of these TRBV4-1+ T cells were diverse. Clonotypic analyses of the reconstituted TRBV4-1+ TCRs demonstrated that the heterogeneity of the CDR3 sequences greatly impacted the strength of CD1c-restricted autoreactivity. Furthermore, cell-free assays using recombinant CD1c loaded with distinct lipids identified several phospholipid species as potential self-ligands. These data provide new insights into the molecular identity of human autoreactive CD1c-restricted T cells.