CD226 and primary cutaneous T-cell non-Hodgkin lymphoma: It is interesting to note that the expression of DNAM1 on NK cells and CD8+ cells in the peripheral blood of CTCL patients was decreased, while DNAM1 levels in the serum were increased, strongly reflecting disease activity, suggesting that soluble DNAM1 in the serum was generated by the shedding of membrane-form DNAM1 (174).