CD4 and inflammatory bowel disease: In particular, primary bile acids such as chenodeoxycholic acid are higher in IBD patients, while secondary bile acids such as lithocholic acid and deoxycholic acid are lower.86 Lithocholic acid is known to inhibit Th1 activation and decrease IFN-γ production by CD4+ T cells.87 The role of secondary bile acids and type I and III IFNs in IBD should be studied in more detail.