A Subset of Human Autoreactive CD1c-Restricted T Cells Preferentially Express TRBV4-1 ⁺ TCRs

Abstract

In humans, a substantial portion of T cells recognize lipids presented by the monomorphic CD1 proteins. Recent studies have revealed the molecular basis of mycobacterial lipid recognition by CD1c-restricted T cells. Subsets of CD1c-restricted T cells recognize self-lipids in addition to foreign lipids, which may have implications in human diseases involving autoimmunity and malignancy. However, the molecular identity of these self-reactive T cells remains largely elusive. Here, using a novel CD1c ⁺ artificial antigen-presenting cell (aAPC)-based system, we isolated human CD1c-restricted autoreactive T cells and characterized them at the molecular level. By using the human cell line K562, which is deficient in MHC class I/II and CD1 expression, we generated an aAPC expressing CD1c as the sole antigen-presenting molecule. When stimulated with this CD1c ⁺ aAPC presenting endogenous lipids, a subpopulation of primary CD4 ⁺ T cells from multiple donors were consistently activated, as measured by CD154 upregulation and cytokine production in a CD1c-specific manner. These activated CD4 ⁺ T cells preferentially expressed TRBV4-1 ⁺ TCRs. Clonotypic analyses of the reconstituted TRBV4-1 ⁺ TCR genes confirmed CD1c-restricted autoreactivity of this repertoire, and the strength of CD1c-reactivity was influenced by the diversity of CDR3β sequences. Finally, alanine scanning of CDR1 and CDR2 sequences of TRBV4-1 revealed two unique residues, Arg30 and Tyr51, as critical in conferring CD1c-restricted autoreactivity, thus elucidating the molecular basis of the observed V gene bias. These data provide new insights into the molecular identity of human autoreactive CD1c-restricted T cells.