Various immune and non-immune cells, as indicated in the top panel, are known to produce IL-10 in mice and humans. Additionally, viruses also carry the homolog of IL-10. Regardless of cellular sources, IL-10 can act only on cells expressing the IL-10 receptor consisting of both IL-10R1 and IL-10R2 components, as shown in the bottom panel. The table within the circle shows major functions of IL-10 mediated by the cell types shown for each function.