Alterations in lipid metabolism accompanied by changes in protein and carotenoid content as spectroscopic markers of human T cell activation

This work aims to understand better the mechanism of cellular processes accompanying the activation of human T cells and to develop a novel, fast, label-free approach to identify molecular biomarkers for this process. Non-activated T-cell activation is a key method in cancer immunotherapy and involves the isolation of T-cells from a patient to perform a specific genetic modification. The standard methodology for confirming the activation state of T cells is based on flow cytometry, antibodies, and target antigens that provide high specificity detection but may show background staining or specific secondary antibody reactions. Here, we evaluated the potential of Raman-based molecular imaging in differentiating non-activated and activated human T cells. Confocal Raman microscopy was performed on activated T cells using chemometrics to obtain comprehensive molecular information, while Stimulated Raman Scattering imaging was used to quickly provide high-resolution images of selected cellular components of activated and non-activated cells. For the first time, carotenoids, lipids, and proteins were shown to be important biomarkers of T-cell activation. We found that T-cell activation was accompanied by lipid accumulation and loss of carotenoid content. Our findings on the biochemical, morphological, and structural changes associated with activated mature T cells provide insights into the molecular changes that occur during therapeutic manipulation of the immune response. The methodology for identifying activated T cells is based on a novel imaging method and supervised and unsupervised chemometrics. It unambiguously identifies specific and unique molecular changes without the need for staining, fixation, or any other sample preparation.