One mechanism of acquired resistance involves somatic mutations, such as loss of beta-2 microglobulin (<i>B2m</i>), that enable tumor cells to evade T cell-mediated killing.<h4>Methods</h4>This study used single-cell RNA-seq, flow cytometry, and <i>ex vivo</i> functional assays to characterize tumor-infiltrating immune cells in antigen presentation-deficient tumors. This evidence concerns the gene B2M and neoplasm.