The variation of natural killer (NK) cell activity and lymphocyte subsets 20 h after a single test dose of α-IFN, was studied in 17 thalassemic patients with chronic hepatitis C. All patients had suspended the α-IFN therapy at least 12 months before the study: 10 were considered responders and 7 nonresponders. Also NK cell cytotoxicity after in vitro incubation with α-IFN was studied. The administration of a single dose of α-IFN increased NK cell cytotoxic activity significantly in the group of responders and in non-responders; moreover the NK cell cytotoxic activity after α-IFN in vitro incubation increased both in responders and nonresponders, but to a lesser degree than in healthy controls. Absolute values of CD4+ and CD8+ lymphocytes decreased significantly only in responders. In conclusion, our data suggest that the variation of NK cytotoxic activity and lymphocyte subsets after a test dose of α-IFN can be considered a parameter related to IFN biological effects.

alpha-interferon (alpha-IFN) has been used to treat chronic non-A non-B hepatitis in thalassaemic patients with response rates from 45% to 83%. Unfortunately, treatment with alpha-IFN is associated with side-effects which have a negative effect on the quality of life of the patient. Therefore it would be useful if we could distinguish in advance those patients who would benefit from such therapy from those who would not. In the present study we found that the modification of lymphocyte subsets 20 h after the administration of the first dose of alpha-IFN revealed that relative numbers of T helper lymphocytes (CD4+) increased in three non-responding patients and decreased in five responding patients, whereas those of T suppressor lymphocytes (CD8+), and natural killer cells (CD57+, CD16+) decreased in non-responding patients and increased in responding patients. Therefore analysis of the lymphocyte subsets CD4, CD8, CD57 and CD16 before and 20 h after the administration of alpha-IFN can be used to predict the clinical response to treatment with alpha-IFN.