Malignant HRS cells from primary HL tumors express TACI and BCMA but not BAFF-R. (A) TACI, BCMA, BAFF-R, CD30, CD40, and CD19 on HRS cell lines. Open and shaded profiles correspond to antibody under study and control antibody with irrelevant binding activity, respectively. (B) The top 4 panels show TACI, BCMA, BAFF-R, and β-actin transcripts, while the bottom 5 panels show TACI, BCMA, BAFF-R, BSAP, and actin proteins in HRS cell lines. Numbers indicate HD-MyZ (1), HD-LM2 (2), L428 (3), KMH-2 (4), and L1236 (5) HRS cell lines. Minus (−) indicates negative control (no cDNA); plus (+), positive control (cDNA from IARC100 lymphoblastoid cell line). (C) TACI, BCMA, and BAFF-R in CD30⁺ HRS cells from a classical HL tumor. DAPI (blue) stains nuclei; asterisks indicate representative CD30⁺ HRS cells. Original magnification ×40. Panel C shows 1 of 15 cases yielding similar results.