In a study of cultured human stem cells infected by Chlamydia trachomatis, the infectious agent of trachoma and venereal disease, inhibition of the cellular biosynthesis of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) was demonstrated to occur through up-regulation of ornithine decarboxylase (Abu-Lubad et al., 2014). This evidence concerns the gene NOS2 and sexually transmitted disease.