CD86 is uniformly and strongly expressed on HRS cells and also on a subset of TAMs. (A) Representative mIF image of a cHL case (CHL24) [inset: PAX5-positive HRS cells with strong CD86 expression]. (B) HRS cells are predominantly CD86-positive (median, 86%; range, 65%-100%) [overlay, density of HRS cells across analyzed cases; median, 243/mm²; range, 55-548/mm²]. (C) Representative mIF image of a cHL case (CHL24) showing weakly CD86-positive TAMs (arrows) [inset, PAX5-positive HRS cells with strong CD86 expression next to CD68-positive TAMs with weaker CD86 expression]. (D) A subset of CD68-positive TAMs is CD86-positive in each case (median, 32%; range, 12%-79%) [overlay, density of TAMs across analyzed cases; median, 1236/mm²; range, 261-2,670/mm²]. (E) CD86 expression is higher on HRS cells (median of mean cell membrane intensity, 4.5; range, 1.7-7.2) than on TAMs (median of mean cell membrane intensity, 1.8; range 1.1-3.1) in each case of cHL (HRS vs TAM, P = .0007). (F) Contribution of cellular CD86 expression in cHL attributable to HRS cells (median, 27%; range, 2%-73%) and to TAMs (median, 73; range, 27%-98%). EBV-positive cases are marked by asterisks. DAPI, 4′,6-diamidino-2-phenylindole.