PRTN3 and leukemia: Finally, immune-mediated mechanisms may also be important for chemosensitivity because ATRA/VP reduces the levels of circulating T cells [5] and members of the neutrophil degranulation network are regarded as a possible leukemia-associated antigen (proteinase 3, PRTN3) and as a regulator of antileukemic immune reactivity (major histocompatibility complex, class I, B; HLA-B).