Objective of study: The pathogenesis of chronic HVB in children is complex and depends on the immunological state of the host. Therefore we followed the evolution of the imunity under the therapy with INF. The aim of the study was to make a correlation between the immunological changes and treatment.

Material and methods. Between 1994-1995 we studied 31 children with chronic HVB. They had AgHBs+, AgHBs-, AgHBe+, AgHBe- and AgHBc-; from these, 10 were treated with classical therapy and 21 were treated with INFalfa2b. Our study methods included: anamnesis, clinical examination, biological trials of the main syndromes involved in liver disorders, the immunological study of the CD3, CD4, CD8, CD19, NK by phenotyping with monoclonal antibody antihuman made in mouse, the IgG, IgM, IgA level by Mancini method. All of these results were statistically analysed. The liver damage was identified by histological examination.

Results: The seroconvertion was noticed in 16 children treated with INFalfa2b, in the other 4 cases it was absent. In the cases with proper evolution the blood levels of NK cells and CD8 lymphocytes were considerably increased (p<0.01 for NK and 0.08 for CD8). We found a strong correlation between the number of blood NK and serum IgG in the cases with seroconvertion. We have no noticed other modification.

Conclusions: 1. The treatment with INFalfa2b in chronic HVB at children is necessary. 2. The mechanism of INF action may be the result of the activation of NK and consequent activation of CD8. 3. The role of the immunomodulatory action of the INF depends on the sensitivity of the body and especially NK cells. 4. The virus persistance in the hepatocytes is a complex mechanism which depends on the natural inability of NK cells to clear it (and can be stimulated by INHF) but a lot of other immune cells may be involved in this process.