Cytotoxic T lymphocyte control during ectromelia (mousepox) virus infection: interaction between MHC-restricted cells analyzed by non-radioactive fluorometry.

Cytotoxic T lymphocyte (CTL) activity of draining lymph node (DLN) cells isolated from BALB/c mice infected with ectromelia virus (EV) was examined using a fluorometric cell-mediated cytotoxicity (CMC) assay. Specific lysis of target cells A20 and EMT-6 primed with EV was demonstrated. The classical CD8+ cytolytic pathway dominated (72.7%) as compared to that of CD4+ (27.3%) in the cellular response during acute EV infection. Also an alternative method for determining CMC, employing a bisbenzamide dye for labelling target cells, is described. Coefficient variations of relative fluorescence were below 6%, that makes the method sensitive and reliable.