Since half of the cHL cases were positive for CD1d in HRS cells, we further investigated the iNKT cell population in cell suspensions of cHL and reactive lymph node (RLN). The mean percentage of iNKT cells was 4% (range 0.8-8%) in cHL and 4% (range 0.4-7%) in RLN (Table II) . iNKT cells were present at similar percentage in either CD1d positive or CD1d negative cHL cases. Two distinct iNKT subsets have been distinguished as Th1 type (CD4 2 iNKT) and Th2 type (CD4 1 iNKT) in terms of cytokine production and cytotoxic activation [10] . We observed a similar percentage of CD41 iNKT cells, i.e., around 50%, in cHL and RLN (Table II) . Given the high expression of CCL17 in HRS cells of cHL [15] and the high expression of the CCL17 receptor, CCR4, on CD41 iNKT cells [16] , it might be speculated that especially the CD41 iNKT cells are present in the close vicinity of HRS cells and might favor the survival and growth of HRS cells. Since it is known that the rosetting CD41CD262 T cells in HL have several features of anergy [17] , the CD1d-restricted iNKT cells might also be dysfunctional or anergic favoring HRS cells survival by escaping from an effective immunosurveillance in cHL. Taken together, we showed expression of CD1d in HRS cells of cHL cell lines and a significant proportion of cHL cases as well as the presence of a marked population of iNKT cells in the reactive background of cHL. The CD1d-iNKT cell axis might play a role in the disturbed immunoregulation in cHL.