The study investigates how the expression of B7-H1 and PD-1 on tumor cells can block the immune system's ability to destroy cancer. B7-H1 is a member of the B7 family and is expressed on many cancers. When B7-H1 is present on tumor cells, it can prevent the effectiveness of certain immunotherapies, such as those targeting CD137. This resistance is due to B7-H1's interaction with PD-1 on T cells, which inhibits T cell activity. However, blocking B7-H1 or PD-1 with specific monoclonal antibodies can reverse this resistance and significantly enhance the effectiveness of immunotherapy. The study suggests that B7-H1 and PD-1 form a molecular shield that prevents T cells from attacking tumor cells. This finding highlights the importance of targeting these molecules in cancer immunotherapy to improve treatment outcomes. The research also shows that B7-H1 can be constitutively or inducibly expressed on tumor cells, and its expression can be regulated by IFN-γ. The study provides evidence that blocking B7-H1 or PD-1 can enhance the immune response against tumors, offering new strategies for cancer treatment. The results indicate that B7-H1 and PD-1 play a critical role in tumor immune evasion, and their inhibition could be a promising approach for improving cancer immunotherapy.The study investigates how the expression of B7-H1 and PD-1 on tumor cells can block the immune system's ability to destroy cancer. B7-H1 is a member of the B7 family and is expressed on many cancers. When B7-H1 is present on tumor cells, it can prevent the effectiveness of certain immunotherapies, such as those targeting CD137. This resistance is due to B7-H1's interaction with PD-1 on T cells, which inhibits T cell activity. However, blocking B7-H1 or PD-1 with specific monoclonal antibodies can reverse this resistance and significantly enhance the effectiveness of immunotherapy. The study suggests that B7-H1 and PD-1 form a molecular shield that prevents T cells from attacking tumor cells. This finding highlights the importance of targeting these molecules in cancer immunotherapy to improve treatment outcomes. The research also shows that B7-H1 can be constitutively or inducibly expressed on tumor cells, and its expression can be regulated by IFN-γ. The study provides evidence that blocking B7-H1 or PD-1 can enhance the immune response against tumors, offering new strategies for cancer treatment. The results indicate that B7-H1 and PD-1 play a critical role in tumor immune evasion, and their inhibition could be a promising approach for improving cancer immunotherapy.