CD8A and neoplasm: Localized delivery using hydrogels in immunotherapy provides adjustable microenvironments for immune cells as it enables the recruitment, expansion, and activation of immune cells in vitro and in vivo (Figure 4; Weiden et al., 2018; Yang et al., 2018) It is reported that a thermosensitive chitosan hydrogel for the delivery of tumor-infiltrating lymphocytes and activated CD8+ T cells.