Interleukin-10 was originally purified from activated CD4+ T helper (Th) 2 cells named cytokine synthesis inhibitory factor).22 Compromised signaling of the IL-10 pathway is associated with inflammatory diseases such as IBD and is often accompanied by immunopathology during infections.23 Interleukin-10-producing B cells have been suggested to be aberrant in SLE or RA.24,25 Human genetic studies further supported IL-10 in controlling intestinal inflammation. Here, CD4 is linked to inflammatory bowel disease.