PD-1 is an inhibitory immune checkpoint that reduces T cell activity by binding to its ligand PD-L1, which facilitates immune evasion in the tumor microenvironment. In recent years, targeting PD-1 has become a key component of cancer immunotherapy. Interleukin-12 (IL-12) serves as a crucial regulatory factor in both innate and adaptive immunity; it promotes cell proliferation, activates cytotoxic lymphocytes and natural killer (NK) cells, boosts the production of interferon (IFN)-γ, and supports cell differentiation, thereby enhancing the generation of TH1-related immunoglobulins. Given its role in pro-inflammatory responses and immune modulation, IL-12 has the potential to convert tumors from a "cold" state to a "hot" state. Therefore, the combination of IL-12 and PD-1 inhibitors represents a promising strategy for advancing cancer immunotherapy. Biocytogen has developed B-hPD-1 plus/hIL12RB1/hIL12RB2 mice by breeding humanized PD-1mice with humanized IL12RB1 and IL12RB2 mice. To validate the PD-1 expression, splenocytes were collected from C57BL/6 mice and homozygous B-hPD-1 plus/hIL12RB1/hIL12RB2 mice stimulated with anti-mouse CD3ε antibody in vivo for 24 hrs. Mouse PD-1 was only detectable in C57BL/6 mice. Human PD-1 was exclusively detectable in homozygous B-hPD-1 plus/hIL12RB1/hIL12RB2 mice, but not in C57BL/6 mice. To validate the functionality of the humanized IL12Rβ1 and IL12Rβ2 receptor complex, CD4+ T cells sorted from splenocytes of C57BL/6 and homozygous B-hPD-1 plus/hIL12RB1/hIL12RB2 mice were stimulated with human IL-12 in vitro, and IFN-γ production was detected by ELISA. Mouse IFN-γ were both increased after responsiveness to mIL-12 in C57BL/6 mice and homozygous B-hPD-1 plus/hIL12RB1/hIL12RB2 mice. Mouse IFN-γ were increased after responsiveness to hIL-12 in homozygous mice but not in wild-type mice.

In summary, the PD-1, IL12RB1, and IL12RB2 genes have been successfully humanized in B-hPD-1 plus/hIL12RB1/hIL12RB2 mice, allowing us to assess the combined efficacy of anti-tumor drugs.