Detection of mitogen-activated T and non-T lymphocytes by virus plaque assay. Virus plaque assay on the cells fractionated by unit gravity sedimentation.

Virus plaque assay (VPA) was utilized for the quantitative evaluation of activated lymphocytes. We examined what types of cells, especially which of activated T and non-T lymphocytes, were detected as infective centres after infection with vesicular stomatitis virus. Marked increases in DNA synthesis and in virus-plaque forming cells (V-PFC) were observed not only during the activation of T lymphocytes with Con A, but also, though to a lesser extent, during the activation with lipopolysaccharide (LPS) of non-T lymphocyte preparations of nude spleen from which theta-positive lymphocytes and macrophages were completely depleted. The latter observation was further confirmed by the VPA on the populations enriched in LPS-activated non-T lymphocytes fractionated by the unit gravity sedimentation method. Fast sedimenting cells were found to be more active in DNA synthesis and contained more infective centres after infection than those sedimenting slowly and original unfractionated cells. Both the capacity for DNA synthesis and virus-replication were considered to be general properties accompanying lymphocyte activation.