As industry knowledge of immunology and its pathways continues to grow, it is becoming increasingly necessary for researchers to have access to high purity, human immune-checkpoint proteins involved in both stimulatory and inhibitory responses. kbDNA's recombinant immune checkpoint libraries include the front - running targets such as PD1 / PDL1 and new proteins of interest like CTLA4 and TIGIT. Our recombinant selection also presents a competitive list of the protein ligands and their correlating pathway's CD antigens. They are expressed mainly in mammalian and are specific to human, mouse, rat and monkey for optimal testing-to-concept experimental design.