Abstract 7473: Flotillin-2 ablation in T cells enhances antigen sensitivity and functionality

Abstract The membrane scaffolding protein flotillin-2 (Flot2) has been proposed to support receptor signaling, but its involvement in T cell receptor (TCR) signaling and T cell responses remains unclear. Here, we show that the deletion of Flot2 increases antigen sensitivity along with changes in surface TCR clustering, resulting in enhanced TCR signaling and effector function to weak TCR stimulation. T cell-specific Flot2-deficient mice showed enhanced proliferation and effector cytokine production in both CD4+ and CD8+ T cells, resulting in better control of tumor growth and infection. However, in vitro TCR stimulation with plate-bound anti-CD3 and soluble anti-CD28 showed increased TCR signaling and early activation of CD4+, but not CD8+ Flot2-deficient T cells upon weak stimulation. In addition, Flot2-deficient CD4+ T cells showed better in vitro polarization toward T helper 1 cells upon weak TCR stimulation, likely due to increased sensitivity of the TCR-triggering threshold. Changes in TCR clustering on the membrane have been suggested to influence the early detection of foreign stimuli and the formation of immune synapses. Flot2 ablation indeed increased the number of membrane TCR nanoclusters on naïve CD4+ T cells. Collectively, this study suggests a mechanism for increasing T cell functionality to weak TCR stimulation by modulating the membrane protein Flot2, which affects surface TCR clustering. These results may have important implications for improving T cell reactivity in diseases with poor antigenicity, such as anti-tumor immune responses. Citation Format: Sookjin Moon, Peer W. Karmaus, Michael B. Fessler. Flotillin-2 ablation in T cells enhances antigen sensitivity and functionality [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7473.