Considering that the red pulp is the major site of chronic LCMV infection and that few infected cells exist in the T-cell zone16,36, these results suggest that stem-like T cells are devoid of antigens, while terminally differentiated T cells interact with infected cells or tumor cells and exhibit cell-killing activity, although their cytolytic function is likely inhibited by the PD-1/PD-L1 interaction37. The gene discussed is PDCD1; the disease is neoplasm.