Tumor infiltrating T cells: complete workflows allow faster and improved analysis

Abstract

T cells can eliminate tumors, but tumor infiltrating (TI) T cells can become intrinsically anergic or extrinsically suppressed. Identifying the mechanisms of T cell dysfunction is necessary to improve immunotherapy efficacy. Mouse tumor models are useful tools in tumor T cell research, but analysis of TI T cells is technically challenging, time consuming and labor intensive. Their frequency can be very low and small populations may escape analysis as they get lost in the background. Importantly, TI T cells are in an antigen-rich and highly immunomodulatory cell environment, such that cell intrinsic functional analysis is hindered. It is fundamental to use new tools to streamline the workflow and generate reliable data. We established workflows combining tissue dissociation, T cell isolation and phenotyping. Tumor dissociation was automated using the gentle MACS™ and optimized for epitope preservation. Enzymatic dissociation was essential for analysis of PD1hiTim3+Lag3+CD39+ CD8 T cells in tumors. Using new T cell-specific microbeads for magnetic cell sorting we increased TI T cell purity by up to 500-fold, while maintaining activation status and phenotype. Importantly T cell isolation from the tumor’s highly immunomodulatory cellular environment was essential to assess cell-intrinsic functional properties. Finally, our data show the use of recombinant RE Afinity antibodies eliminated non-specific labeling of cells in the tumor microenvironment. We conclude that standardized processing of tumor samples and magnetic isolation of tumor infiltrating T cells greatly reduces time and cost of total workflow and downstream analysis while significantly increasing reproducibility and the quality of data obtained from TIL analysis.