In contrast, CD1d was detected in all four cHL cell lines, varying from weakly positive in U-HO1 to strongly positive in the other three cHL cell lines ( Fig. 1C-F) . By flowcytometry, we validated that CD1d was present on the membrane in cHL cell lines (data not shown). In normal tonsil tissue, CD1d staining was observed mainly in the MZ and showed no positive staining in the GC (Fig. 1G ) consistent with the reported results [14] . CD1d was detected in HRS cells in 21 out of 44 cHL cases (48%) (Fig. 1H , Table I,  Supporting Information Table I) , showing both cytoplasmic and membranous staining. No correlation was found with EBV status and CD1d expression (Table I) . CD1d was also positive in the reactive background, usually in more than half of the reactive cells. Nine of the 39 NHL cases were positive for CD1d (23% , Table I ), i.e., in three out of 19 GC B cell derived NHL and in six out of 20 non-GC B cell NHL (Table I, Supporting Information Table I ). The CD1d expression in HL is remarkable since GC B cells and the majority of the GC B cell derived NHL are negative. Positivity of HRS cells indicates that these cells might have acquired CD1d expression during malignant transformation. CD1d expression has been detected in some B cell malignancies, such as CLL [4] and multiple myeloma [5] . In these B cell malignancies, iNKT cells activated by a-GalCer loaded CD1d1 tumor cells resulted in the induction of apoptosis of the tumor cells in vitro [4, 5] .