A. Gene expression analysis of microdissected HRS (GSE-39133) reveals high expression of CD123 as compared to controls (microdissected germinal center B cells) B. Primary samples of Hodgkin lymphoma were stained for CD30 and CD123 by immunohistochemistry (IHC). Expression of CD123 was found of the HL Reed-Sternberg cells but also in the tumor microenvironment, as opposed to CD30 that was only positive on HRS. C. CD123 was expressed on tumor-associated macrophages by IHC (left), dual IHC (right, top; brown CD68 and red CD123) and immune fluorescence (right, bottom; red CD123 and green CD68. D. RNA expression of CD123 and CD68 (left) and CD11b (right) in 130 whole HL biopsies (GSE17920): a strong correlation between macrophage markers (CD68, CD11b) and CD123 expression was observed. E. High CD123 protein expression on 4 standard HL cell lines (HDLM-2, KM-H2, SUP-HD1 and L428) by flow cytometry.