In the last years immunological aspects are studying in the pathogenesis of infectious diseases. The influence of immune response to the infectious processes of acute and chronic virus infectious (Hemorrhagic Fever with Renal Syndrome and Chronic Viral Hepatitis C, as an example) has been revealed. Misbalance of system and local cytokine status characterizes the direct influence of immune system to all organs and systems of human organism. It determines the severity of the disease and its outcomes.