A compound attribute that is the ratio of amount of cytotoxic and regulatory T-cell molecule (human) in blood to amount of programmed cell death protein 1 (human) in blood. The trait is CRTAM/PDCD1 protein level ratio in blood (OBA_2054511, an Ontology of Biological Attributes entry). Also known as: the ratio of amount of cytotoxic and regulatory T-cell molecule (human) in blood to amount of programmed cell death protein 1 (human) in blood.