Leukocyte subpopulations were characterized by immunohistochemistry in immune-related psoriasis induced by anti-PD-1 and compared to those present in chronic plaque-type psoriasis (n=6 patients) and in paradoxical skin lesions of HS patients undergone anti-TNF-α therapy (n=3) (Figures 2, 3). Here, PDCD1 is linked to histiocytic sarcoma.