To characterize the immune signature of skin-infiltrating cells in more detail, we analyzed key transcription factors involved in type 1 and type 2 cell development, as well as IL-17A production by T cells and granulocytes in PV, BP and LP on tissue microarrays (TMA) of skin lesions using immunofluorescent antibody staining. This evidence concerns the gene IL17A and acquired polycythemia vera.