Use of lysates from pooled human mononuclear cells to activate CD3 T cells in humanized mice with low human cell engraftment efficiency.

In regenerative medicine, humanized mice (hu-mice) are extremely valuable for verifying the cross talk between immune cells and therapeutic cells. Given the highly dynamic nature of the activities of immune cells, the in vitro platform does not allow for screening of their exact interactions with different therapeutic cells. By contrast, hu-mice have been widely applied for in vivo studies, especially those on immune rejection. However, the full reconstitution of lymphoid lineage cells in hu-mice remains to be realized. In this study, we investigated whether lysates from healthy donor-derived pooled mononuclear cells (MNCs) can promote the increase of lymphoid lineage cells in hu-mice. The pooled MNC lysate treatment of hu-mice possessing a low proportion of CD45 cells resulted in significant increases in CD3 cells and CD45 cells with the RO phenotype. The diverse epitopes from the pooled MNC lysates significantly induced the proportion of lymphoid lineage cells in the thymus and spleen after therapeutic cells with mismatched HLAs were co-injected into the hu-mice. These findings demonstrate the technical benefits of using pooled MNC lysates for reconstituting lymphoid lineage cells in hu-mice, providing a valuable in vivo platform for investigating the cross talk between lymphoid immune cells and therapeutic cells.