PVM-specific IFN-γ-secreting (A) and IL-5-secreting (B) splenocytes following in vitro restimulation with PVM-infected cell lysates. Five to six week-old Balb/c and C57Bl/6 mice were inoculated with medium, 30 pfu (Balb/c) or 300 pfu (C57Bl/6) and sacrificed on days 14, 28, and 42 p.i.. The PVM-specific response is calculated by subtracting the number of cytokine-secreting cells restimulated with mock-infected cell lysates from those restimulated with PVM-infected lysates. The data points represent individual animals, with the median indicated by a line. **, p <0.01.