CD4 and infection: A significant increase (p<0.05, n = 5) in the percentages of TGF-beta+CD4+ T cells was observed in the spleens of MDV infected birds at 21 dpi (Fig 5D and 5E), while there was no difference in the percentages of total CD4+CD25+ T cells (Fig 5B) or CD4+CD25high T cells (Fig 5C) between the infected and mock infected birds at any time points post infection.