Natural interferon alpha derived from normal human white blood cells (Le-IFN
) consists of at least 15 different naturally occuring proteins (subtypes INF
) and some of them are glycosylated. These are the same IFN
subtypes produced by the human body after the contact of the white blood cells with external agents for example viruses. Till now the results of 18 studies were published which assessed the efficiacy of the combination Le-IFN
and ribavirin. These studies present 45 patients by IFN
not yet treated (naive) patients, 212 patients in relaps state and 528 non responders .The results confirmed minimally the same efficiacy of that combination in comparison with the most often used recombinant IFN
(rIFN
) and ribavirin treatment. According to the published papers the adverse effects during treatment by Le-IFN
was of similar type like in others IFN
treatment but significantly less frequent and lower intensity. According to the results of clinical studies the lowering of the white blood cells and platelets were minimal during Le-IFN
treatment. For this reason this type of IFN
was useful for treatment of patients with low initial level of these blood elements. During treatment by Le-IFN
the quality of life was significantly better in comparison with rIFN
treatment and better tolerated by the patients. For this reason the combined treatment by Le-IFN
and ribavirin is useful for patients who badly tolerated previous treatment by rIFN
or when a worse tolerance is expected. Treatment by Le-IFN
is able to restore the therapeutic response in these patients where resistance to rIFN
appeared as a result of neutralising antibody anti-IFN
development.

        Key words: leukocyte interferon alfa – chronic hepatitis C – antibody to interferon – side effects of treatment by interferon alfa