AIM:In the present study,antibody and peripheral blood mononuclear cells (PBMC) proliferative responses against hepatitis C virus (HCV) antigens were evaluated in HCV chronically infected patients. METHODS:Paired serum and PBMC samples were taken six months apart from 34 individuals,either treated or not,and tested by enzyme-linked immunosorbent assay (ELISA) and carboxyfluorescein succinimidyl ester staining. RESULTS:Over 70% of the patients showed specifi c IgG and IgM against capsid,E1 and NS3,while HVR-1 was recognized by half of the patients. An increase in the levels of the anti-capsid IgM (P = 0.027) and IgG (P = 0.0006) was observed in six-month samples,compared to baseline. Similarly,a signifi cantly higher percent of patients had detectable IgA reactivity to capsid (P = 0.017) and NS3 (P = 0.005) after six months,compared to baseline. Particularly,IgA against structural antigens positively correlated with hepatic damage (P = 0.036). IgG subclasses evaluation against capsid and NS3 revealed a positive recognition mediated by IgG1 in more than 80% of the individuals. On the contrary,less than 30% of the patients showed a positive proliferative response either of CD4+ or CD8+ T cells,being the capsid poorly recognized. CONCLUSION:These results confi rm that while the cellular immune response is narrow and weak,a broad and vigorous humoral response occurs in HCV chronic infection. The observed correlation between IgA and hepatic damage may have diagnostic significance,although it warrants further confi rmation. AIM: In the present study, antibody and peripheral blood mononuclear cells (PBMC) proliferative responses against hepatitis C virus (HCV) antigens were evaluated as HCV chronically infected patients. METHODS: Paired serum and PBMC samples were taken six months apart from 34 individuals, either treated or not, and tested by enzyme-linked immunosorbent assay (ELISA) and carboxyfluorescein succinimidyl ester staining. RESULTS: Over 70% of the patients showed specifi c IgG and IgM against capsid, E1 and NS3, while HVR-1 was recognized by half of the patients. An increase in the levels of the anti-capsid IgM (P = 0.027) and IgG (P = 0.0006) was observed in six-month samples, compared to baseline. Similarly, a signifi cantly higher percent of patients had Particularly, IgA against structural antigens positively correlated with hepatic damage (P = 0.036). IgG subclasses evaluation against capsid an On the contrary, less than 30% of the patients showed a positive proliferative response either of CD4 + or CD8 + T cells, being the capsid poorly recognized. CONCLUSION: These results confi rm that while the cellular immune response is narrow and weak, a broad and vigorous humoral response occurs in HCV chronic infection. The observed correlation between IgA and hepatic damage may have diagnostic significance, although it warrants further confi rmation.