CD4 and viral infectious disease: It is not known whether NK cells can display memory responses against any other viral infections and if they do, whether it is B- and T- lymphocyte independent since it has been shown that NK cell mediated protection induced by DCs is dependent on CD4+ T cells [10] and increased proliferation and activity in rabies Ag re-exposed human NK cells depend on IL-2 signaling derived from memory CD4 T-cells [12].