Abstract B030: Altered distribution of double-negative T cell subsets in pediatric acute lymphoblastic leukemia

Abstract Objective: Double negative T (DNT) cells are a unique and rare subset of T lymphocytes that do not express both CD4 and CD8 co-receptors. With growing interest in the antitumor effect of DNT cells and ongoing clinical trials in acute myeloid leukemia, it is also important to understand how DNT cells are involved in other hematologic malignancies. In particular, the role of DNT cells is underexplored in children with acute lymphoblastic leukemia (ALL). We aim to characterize the distribution of DNT cells and their subsets in the peripheral blood of children with ALL compared to healthy controls using flow cytometry. Methods: In this single-center, cross-sectional study, we recruited 54 children with ALL and 46 age and sex-matched healthy controls. Fluorochrome-conjugated antibodies against CD3, CD4, CD8, CD19, CD56, TCRαβ, and TCRγδ were used to identify the frequency of conventional lymphocytes and DNT cells in the blood. Statistical analysis involved the Mann-Whitney U test and Spearman correlation. Results: ALL patients had significantly lower total number of DNT cells compared to controls (median 2.9% vs. 4.8%, p < 0.0001). The γδ+ DNT cells were markedly decreased in ALL (p < 0.0001), whereas αβ+ DNT cells demonstrated a mild elevation, though statistically non-significant (p = 0.257). In addition to altered DNT subsets, the absolute count of double-positive T cells was also comparatively reduced in patients with ALL (p = 0.042). We observed a positive correlation between absolute DNT count and white blood cell count (r = 0.709, p < 0.0001); however, no significant association was seen between baseline blast count and relative DNT (r = -0.118, p = 0.434). Conclusion: We observed an altered DNT profile in children with ALL, especially characterized by significant depletion of γδ+ DNT cell subset. Considering the reported antitumor capacity of DNT cells in the literature, such an imbalance in subset distribution may suggest immune dysregulation or suppression in the leukemic microenvironment. Additional studies are needed to confirm the immunological significance of our findings further and to elucidate the potential role of DNT cells in ALL. Citation Format: Kuanysh Dossybayeva, Dana Tleugozhina, Gulsamal Zhubanova, Assel Mussayeva, Assem Kurmangali, Ayana Ablayeva, Dair Nurgaliyev, Zabira Kyzdarbekova, Kundyz Shaykhyzada, Galiya Nauryzbayeva, Ulbolsyn Orumbayeva, Kadisha Nurgaliyeva, Matthew Tanko, Dimitri Poddighe, Lyudmila Akhmaldtinova. Altered distribution of double-negative T cell subsets in pediatric acute lymphoblastic leukemia [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Discovery and Innovation in Pediatric Cancer— From Biology to Breakthrough Therapies; 2025 Sep 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl_2):Abstract nr B030.