IFNA1 and infection: This explains the impossibility to culture ATL cells in vitro and the effectiveness of the AZT/IFN combination in vivo but not in vitro. Similarly, the AZT/IFN combination, through inhibition of de novo infection of circulating CD8+ lymphocytes, that are subject to killing by virus specific CTL [66], may protect the immune system from the fratricide among these virus-specific CTLs, allowing therefore disease control by the immune system.