Immunopathologic mechanisms leading to liver tissue injury in hepatitis caused by hepatitis A virus (HAV) were studied in an autologous in vitro model. Data show virus-specific killing by liver-infiltrating T lymphocytes in man and support the hypothesis that hepatocellular damage as well as efficient elimination of virus-infected hepatocytes is mediated by HLA-restricted, HAV-specific CD8+ T lymphocytes. Furthermore, experimental results demonstrate that human interferon-gamma produced by HAV-specific T cells may act as a key factor in T-cell-promoted clearance of HAV-infected hepatocytes. Besides the well-known hepatotropism, the myelotropic properties of HAV have some important clinical implications. Perturbations of hematopoietic regulation, ranging from transient granulocytopenia to rare cases of bone marrow failure, are associated with HAV infection. In an attempt to elucidate the pathogenetic mechanisms, we could show a direct suppressive effect of HAV on human bone marrow progenitors and a significant progressive decline in these cells in HAV-infected long-term bone marrow cultures.