Figure 3.

Schematic view of the complex role of macrophages in Xenopus host defenses against RV. As innate immune cell effectors, macrophage can acquire viral antigen by direct infection, pinocytosis of opsonized viruses or phagocytosis of infected cells, as well as release cytokines, chemokines and toxins that contribute to limiting the infection. As an adaptive immune cell effector, macrophages process and present viral antigens through MHC class I and class II pathways, up-regulated co-stimulatory molecules (B7, CD40) and activate anti-RV CD8 and CD4 T cells. Finally, macrophage can harbor quiescent RV in asymptomatic frogs.