Fig. 2
Immune monitoring strategies for patients receiving checkpoint blockage therapy. Technologies that are currently used to assess the potential immune biomarkers. a Tumor and immune cells in tumor specimens could be evaluated by immunohistochemical stain (IHC) or immunofluorescence assays, molecular or genetic profiling analysis, and cellular functional assays. The tumor microenvironment can be dissected histopathologically to characterize spatial relationships between tumor and immune infiltrates. Transcriptional profiling assays can evaluate changes in gene expression in both the tumor cells and lymphocytes. Deep sequencing techniques enable quantification of changes in individual T/B cell clonotypes. b Peripheral blood provides a minimally invasive way to allow serial monitoring of dynamic changes of immune biomarkers during cancer immunotherapy. The analysis of changes in cell counts with therapy, changes in cytokine levels, circulating tumor cells, tumor-derived nucleotides, and immune cells. c Flow cytometric analysis of TILs anPBMCs for quantitating the effect of therapy on immune subsets such as activated CD8 + PD1+ T cells, CD4 + FOXP3 + CD25hi Tregs, or myeloid-derived suppressor cells. Using polychromatic flow cytometry, multiple surface and intracellular markers can be detected, allowing in-depth characterization of T cell phenotype and activation state. d Multifunctional flow T cell assay, MHC tetramer staining and ELISPOT can be used to analyze the presence and function of tumor-specific T cell subpopulations. Abbreviations: PD-L1 programed death-1, IHC immunohistochemistry, ELISPOT enzyme-linked immunospot assay, CTCs circulating tumor cells, WES whole exome sequencing, NGS next-generation sequencing, TIM-3 T cell immunoglobulin domain and mucin domain, LAG lymphocyte-activation gene, ICOS inducible costimulators, MDSC myeloid-derived suppressor cells, HLA human leukocyte antigen