Azathioprine, or 6(1-methyl-4-nitro-5-imidazolyl) thiopurine, affects the immune response by inhibiting the division of activated B and T lymphocytes.
Once assumed, it is converted in 6-mercaptopurine (6-MP) by red blood cell glutathione. 6-MP is then converted into a series of mercaptopurine-containing nucleotides, which interfere with the synthesis of DNA and polyadenylate-containing RNA: they can be incorporated into nucleic acids and can produce chromosome breaks, as well as interfere with the synthesis and action of coenzymes. So, they block lymphoid cell mitosis and suppress immune reactivity.