KLRD1 and Behcet disease: Regarding NK cell activation, inhibitory CD34/NKG2A and activating CD94/NKG2C molecules are alternatively expressed on NK, CD4+CD8+ T cells, as indicating an imbalance in cytotoxic activity in BD patients [46], although the function of NK cells is supposed to be down-regulated in the active stage and to be up-regulated in the remission of BD patients [47].