CD274 and cyclic hematopoiesis: PD-L1 has a priority in controlling the interaction of T-cells and antigen-presenting cells, inhibiting PD-L1-Enhanced hapten-induced Contact Hypersensitivity (CH) in a mouse model, and increasing the number of T-cells in draining lymph nodes, whereas PD-L2 inhibition did not show a similar strengthening effect.7