| Background: The infection of HCV is characterized with chronicity. With a long-term of HCV infection, the illness may develop to HCV carrier ,chronic hepatitis, liver cirrhosis, and primary liver carcinoma step by step. So far the reason that many patients develop to persistent HCV infection is poorly understood . Specific immunity to HCV may play an important role in the process.As we know ,specific cellular immunity has an important role in clearing the HCV of intra-cell ,which may be correlated with the HCV self-restricted infection and contribute to hepatocyte injury . On the other hand,specific humoral immunity to HCV,such as anti-HCV HVR1, also play an important role in clearing HCV.However the role of antibodies to HCV antigens except HCVHVRl remains unkown.Aims: In order to invesgate the distribution of IgG subclasses and it's significance in chronic HCV infction, different recombinated HCV antigens were used to detect the corresponding specific IgG subclasses,antibody affinity were also assayed at the same time . Then the data from different groupes infected with genetype Ib or no-genetype Ib and patients with different efficiency to IFN- alpha treatment were analysed and evaluated.Materials and methods:1.Patients: All the serum samples were negetive for anti-HAV, anti-HEV ,anti-HBV-M, and positive for anti-HCV and HCVRNA.60 samples with HCV infection over one year were selected as research objects,20 among the 60 samples with chronic HCV infection received IFN-alpha treatment subsequently.2. Identifying HCV genotype : According to Simmonds'methods, HCV genotypes were identified la, Ib, 2a, 2b, 3a, 3b, 4, 5 and 6. 50 patients in our study were infected with genotype Ib.The others were infected with no-genotype Ib.3 IgG subclasses to core ,NS3,NS4,NS5 assay: The IgGl,IgG2,IgG4 specific to core ,NS3,NS4,NS5 were detected by ELISA at 37 ,using different recombinated HCV antigens.IgG3 to core ,NS3,NS4,NS5 were detected by ELISA 4 IgG subclasses affinity assay: The serum with positive IgG subclass were selected for antibody affinity assay.Treatment with urea was carried out after the reaction of the serum antibodies with different recombinated HCV antigens.The OD value which were detected with and without urea treatment were evaluatedAntibody affinity index=ODValue(with urea treatment)/OD value(without urea treatment) X 100%.5 Total IgG subclass assay.Total IgG subclass were detected by ELISA using 0.4 u g mouse to human IgGl ,IgG2,IgG3,IgG4 monoclonal antibody as coaling antigen.Results:1 Temperature has important impact on the specific IgG3 detection.The OD value detected at 4 were higher than those detected at 37 "C.2 The OD value of the specific IgGl,IgG3 were higher than that of the specific IgG2,IgG4 in all the samples from chronic HCV infection.3 Antibody affinity index to specific IgG3 (10.2%-17.4% )were lower than that to specific IgGl,IgG2 ,IgG3 (>30%). The line-regression assay indicated that there was some correction between IgG3 antibodies and ALT level,especial anti-NS3 IgG3.4 There was no difference in IgG subclasses distribution between the groups with HCVgenotpe Ib and no-HCV genotype Ib. The OD value of anti-NS5IgGl among those had response to IFN-a treatment were significant higher than those who had no response to IFN-a treatment.5 The OD values of total IgG subclasses detected in the group infected with HCV were higher than those of control group. Primary IgG subclass deficiency is rare in the patients persistent infected with HCV.Conclusions:1 The specific IgG3 to core ,NS3,NS4,NS5 are a kind of antibody with low affinity .And the affinity index of the specific IgGl,IgG2,IgG4 were higher than that of specific IgG3.2 The specific IgG subclasses in patients with chronic HCV infection were restricted to IgGl and IgG3. It suggests that there be disequilibrium of the Thl/Th2 subsets in the patients,and this may contribute to the HCV persistent infection.3 IgG3, especially anti-NS3IgG3, may correlate with hepatocyte inj...
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