biostudies-literatureAoki TJapan Society for the Promotion of Science LondonJapanese Leukemia Research FundMasato Kawano Memorial Public Interest Foundation for Promotion of PediatricsChiba UniversityJapan Society for the Promotion of Science2223-2233https://www.ebi.ac.uk/biostudies/studies/S-EPMC7385353biostudies-literatureUnknown111(7)Invariant natural killer T (iNKT) cells are innate-like CD1d-restricted T cells that express the invariant T cell receptor (TCR) composed of Vα24 and Vβ11 in humans. iNKT cells specifically recognize glycolipid antigens such as α-galactosylceramide (αGalCer) presented by CD1d. iNKT cells show direct cytotoxicity toward CD1d-positive tumor cells, especially when CD1d presents glycolipid antigens. However, iNKT cell recognition of CD1d-negative tumor cells is unknown, and direct cytotoxicity of iNKT cells toward CD1d-negative tumor cells remains controversial. Here, we demonstrate that activated iNKT cells recognize leukemia cells in a CD1d-independent manner, however still in a TCR-mediated way. iNKT cells degranulated and released Th1 cytokines toward CD1d-negative leukemia cells (K562, HLCancer scienceActivated invariant natural killer T cells directly recognize leukemia cells in a CD1d-independent manner.PMC7385353Therapeutics Research Initiative Grant/2018-Y7,Therapeutics Research Initiative Grant/2018‐Y7,Research award for young researchersKAKENHI/18K16108Hara ATakatani TMotoyoshi KKiuchi MMotohashi SShimojo NIshii ATakami MNakayama THino MAoki TToyoda TOkada RHirahara KKoyama-Nasu RKimura MYfalseActivated invariant natural killer T cells directly recognize leukemia cells in a CD1d-independent manner.Invariant natural killer T (iNKT) cells are innate-like CD1d-restricted T cells that express the invariant T cell receptor (TCR) composed of Vα24 and Vβ11 in humans. iNKT cells specifically recognize glycolipid antigens such as α-galactosylceramide (αGalCer) presented by CD1d. iNKT cells show direct cytotoxicity toward CD1d-positive tumor cells, especially when CD1d presents glycolipid antigens. However, iNKT cell recognition of CD1d-negative tumor cells is unknown, and direct cytotoxicity of iNKT cells toward CD1d-negative tumor cells remains controversial. Here, we demonstrate that activated iNKT cells recognize leukemia cells in a CD1d-independent manner, however still in a TCR-mediated way. iNKT cells degranulated and released Th1 cytokines toward CD1d-negative leukemia cells (K562, HL2020-01-01T00:00:00Z2020 Jul2025-04-04T07:40:40.188Z2025-04-04T07:40:40.188ZS-EPMC73853533232431510.1111/cas.14428