CD4 and infection: Käser et al. provided a detailed view of the porcine T-cell immune response to Cs and Ct. As in humans, pigs develop a strong CD4+ T-cell response upon Ct or Cs infection consisting of mainly IFN-γ single- or IFN-γ/TNF-α- double-cytokine producing CD4+ T cells; this response was heterologous, thus, Cs infected pigs responded to Ct and vice versa [11].