PDCD1 and systemic lupus erythematosus: In humans, PD-1 also known as cluster of differentiation (CD279), human systemic lupus erythematosus (hSLE1) and systemic lupus erythematosus 2 (SLEB2) [1] is encoded by the PDCD1 gene located at chromosome 2:241,849,881–241,858,908 reverse strand [13].