Identification of cytolytic lymphocytes in West Nile virus-infected murine central nervous system

Inflammatory cells were isolated from West Nile virus (WNV)-infected CBA/H (H-2k) mouse brains, and their function and cell surface markers were studied. Two populations of cytolytic lymphocytes were detected. One population, which lysed WNV-infected and uninfected L929 (H-2k), YAC-1 (H-2a), P815 (H-2d), OH (H-2KdDk) and 2R (H-2KkDb) target cells, had a phenotype of L3T4- Lyt2- Thy1 +/- asialo GM1+ and hence were natural killer (NK) cells. The other, which lysed WNV-infected cells to a greater extent than uninfected L929 cells, had a phenotype of L3T4- Lyt2+ Thy1+ asialo GM1- and were cytotoxic T cells. In addition, the presence of the latter population was demonstrated by the specific lysis of syngeneic WNV-infected astrocytes, a cell type which is resistant to NK cell lysis. The cell surface markers of isolated inflammatory cells were determined by two colour flow cytometry. This showed that 15 to 40% of the cells were Thy1+, among which about 3% were Lyt2+. No L3T4+ cells were detected.