As previously reported [17], injection of effector HBV-specific CD8 T cells (derived from immunized syngeneic non transgenic mice, see Methods) into saline-treated control mice caused a transient liver disease (monitored biochemically by measuring the serum activity of alanine aminotransferase [sALT], an enzyme that is released into the circulation by necrotic hepatocytes) that almost completely resolved 5 days after transfer (Figure 1A). The gene discussed is CD8A; the disease is liver disorder.