Early replication of Friend leukaemia viruses in spleen macrophages.

The ability of spleen macrophages to support Friend leukaemia virus replication was studied by testing for infectivity in adherent cells obtained from mice at various times after infection. Virus-releasing macrophages appeared early after infection and reached a high proportion. The released virus was probably synthesized de novo since macrophage infectivity was strongly reduced by treatments which affected cellular viability or synthetic activities and electron microscopy showed C-type particles budding from macrophages.