Skip to main content
Dryad

CD64 enables TCR-dependent, MHC-independent CTL cytotoxicity of AML cells

Abstract

CD8+ T cell-mediated cytotoxicity classically occurs through engagement of an alpha-beta T cell receptor (TCRab) with a peptide-class I major histocompatibility complex (pMHC). However, it is also known that cytotoxic CD8+ T lymphocytes (CTLs) can kill tumor cells in a pMHC-independent manner. The relative physiologic contribution and biological significance of pMHC-independent CTL killing remains unclear, and a receptor shared between CTLs and NK cells is generally invoked as the mechanism by which this occurs. In this study, we used acute myeloid leukemia (AML) as a model to examine mechanisms of pMHC-independent cytotoxicity and discovered a paradoxical TCR-dependent, MHC-independent mechanism that requires CD64. Utilizing knockouts of potential AML ligands and CTL receptors, we demonstrate that pMHC-independent cytotoxicity is a potent mechanism of CTL-mediating killing of AML cells and is largely restricted to CD64-expressing cells through an IFNg-regulated process. Notably, we found that pMHC-independent CTL killing is not due to activation of commonly implicated NK activating receptors but rather requires an activated TCRab/CD3 complex. Thus, we identify a novel form of CD64-dependent, pMHC-independent, TCR-dependent killing by CTLs that appears highly enriched for in AML.