IL6 and viral infectious disease: Secretion of IL-6 by macrophages is known to play an indirect immunoregulatory role in the immune response to viral infection [19], and TNF-α acts as an inflammatory cytokine by triggering a cascade of cytokine production [20] Since both IL-6 and TNF-α are downregulated by E. faecium in SwIV-infected 3D4/21 cells, the reduced inflammatory response caused by some cytokines at the cellular level may contribute to the antiviral effect of the probiotic.