The invention provides a method of producing mature dendritic cells in vitro,which comprises the step of culturing the immature dendritic cells in thepresence of a specifically configured high molecular weight double strandedRNA (dsRNA) polymer. The specifically configured high molecular weight dsRNApolymer is typically selected from the group comprising poly [I]:poly [CxU]；poly [I]:poly [GxU]； poly [A]: poly [UxC]； poly [A]:poly [UxG]； poly [U]:poly[AxC]； poly [U]:poly [IxU]； poly [C]:poly [GxA]； poly [C]:poly [GxU]； poly[G]:poly [CxA]； poly [G]:poly [CxU] and Ampligen, where x is on average anumber from 3 to 40. The immature dendritic cells may be exposed to an antigenbefore they are matured, and a vaccine including the antigen-presenting maturedendritic cells can then be prepared. A method of treating cancer, a virus,parasite and microorganism is also disclosed.
