The aims of the presented manuscript are schematically summarized in Figure 1: We wanted to (i) develop and functionally characterize a TM for redirection of UniCAR T cells to CD19 positive tumor cells (Figure 1A) and (ii) challenge the idea to manufacture the TM in vivo from the producer cell line housed in a starPEG-heparin cryogel (Figure 1B) for retargeting of UniCAR T cells in experimental mice (Figure 1C). The gene discussed is CD19; the disease is neoplasm.