Intracytoplasmic expression of IFN-? by sub-populations of peripheral T cells in HAV and Sham-vaccinated calves. Percentage of live CD4+ (squares), CD8 + (triangles) WC1 + (crosses) expressing IFN-? after 24 h stimulation with PPD-J from A. HAV vaccinated calves B. Sham vaccinated calves including samples taken week -11, immediately prior prime vaccination; week -5, immediately prior boost vaccination; week 0, immediately prior to MAP challenge and up to 36 weeks post challenge. Significant differences between groups in A. and B. of P < 0.05 are indicated as ¿ (CD4+), * (CD8 +), ? (WC1 +) for each time point.