CTSB and leprosy: In addition to these three antimicrobial pathways, several genes encoding products that have microbicidal functions were also found to be associated with leprosy, such as the lysosomal cysteine protease encoding gene CTSB (cathepsin B) (117), the antimicrobial peptide encoding gene DEFB1 (beta-defensin 1) (118) and the IFNG gene (119, 120).