The cell type predominantly infected by maedi-visna virus (MVV) is the
macrophage, and we have looked at the ability of MVV-infected macroph
ages to interact with cytotoxic T lymphocytes (CTL), important effecto
r cells against virus infections. MVV-specific CTL precursors were det
ected, after in vitro culture with MVV antigen and recombinant human i
nterleukin-2, in peripheral blood lymphocytes of all MW-infefted sheep
. MVV-infected monocyte-derived macrophages and alveolar macrophages w
ere able to stimulate CTL activity in vitro and were targets far these
activated CTL. The major effector cell population using MVV-infected
macrophage targets was CD8(+) lymphocytes, although another population
, lymphokine-activated killer cells, may also have been involved. Ther
e was no direct cytotoxic activity found in alveolar lymphocytes from
MVV-infected sheep without lung lesions.