Characterization of the Two Populations of NK-Like CD56⁺ T Cells and KIR⁺ T Cells in Human

Abstract 3292

Previous studies have demonstrated that many T cell subsets possess NK-like features, including the CD56⁺ and KIR⁺ populations. Collectively, these studies showed that these NK-like T cells are predominantly αβ⁺ CD8⁺ with memory phenotype and could recognize HLA-E associated viral peptides after expansion upon TCR engagement. However, their clonality, transcriptome, regulation, specificity, and memory response in human have not been fully elucidated. We hypothesize that these NK-like T cells are phenotypically and functionally distinct from conventional T and NK cells and they play unique roles in virus and cancer control. Herein, we extensively characterized the CD56⁺ T cells and the KIR⁺ T subset by analysis of TREC, TCRVβ spectrum, telomere length, surface biomarkers, genome-wide transcriptome, multi-analyte cytokine profiling, cancer cell susceptibility, tetramer staining, and real-time response to CMV reactivation in stem cell transplant recipients. In contrast to CD56^– T cells, CD56⁺ T cells are limited in TREC, TCRVβ, telomere length, cytokine secretion, transcription of metabolic genes stx6, nnt, galnt2, hvcn1, tyms, rpa1 tmf1, ecop, and tspan3, and are mostly KIR⁺, CD8⁺, DNAM1⁺, NKG2D⁺, CD44⁺, NKp46^– and CD25^–. Compared to KIR^– CD56⁺ T cells, KIR⁺ CD56⁺ T cells are even more limited in TREC, TCRVβ, telomere length, and cytokine secretion, but have elevated transcription of NK cytotoxicity-related genes arrb1, ppp3cc, and lamc3, higher degranulation after activation by IL-2/IL-15 and CD3/CD28 antibodies, better killing of cancer cells after cytokine priming, and are mostly KIR2DL2/3⁺, NKG2D⁺, NKp46⁺, CD16⁺, NKG2C⁺, CD57⁺, and 2B4⁺. Importantly during CMV reactivation after stem cell transplantation, the percentage of KIR⁺ CD56⁺ T cells in the patient's blood increased dramatically and was significantly higher (p=0.0021) than in those without viral reactivation. Ex vivo, KIR⁺ CD56⁺ T cells demonstrate CMVpp65 tetramer staining, memory response to CMV peptides, and potent lysis of CMVpp65-pulsed target cells dependent on both KIR and TCR specificity. Furthermore, we identified for the first time that KIR^– CD56⁺ T cells are Rorc⁺ IL-13-secretor. In conclusion, both CD56⁺ and KIR⁺ NK-like T-cell subsets are unique in biological and clinical properties and have distinct roles in cancer and infection control.