At 14 dpi, ducks were bled to determine the peripheral T-lymphocyte proliferative response to TMUV infection (Fig. 4d), and the levels of IFN-γ (Th1-type cytokine) and IL-4 (Th2-type cytokine) in serum (Fig. 4e) were also determined. The gene discussed is IL4; the disease is infection.