IL2 and neoplasm: Since tacrolimus is known to inhibit T-cell proliferation by reducing IL-2 release from the lymphocytes11, the tumour that formed in the presence of tacrolimus was considered to express major antigens that stimulate T cells, such as major histocompatibility complex class I. Importantly, undifferentiated iPSCs express low levels of major histocompatibility complex class I antigen, which increase following differentiation to induce a T-cell dependent immune response in allogeneic cell transplantation models12, 13.