The 3′UTR 1188 A/C polymorphism in the interleukin-12p40 gene (IL-12B) is associated with lepromatous leprosy in the west of Mexico

Leprosy is a chronic infectious disease caused by Mycobacterium leprae. IL-12 participates in the immune response against M. leprae by regulating T cell differentiation into the Th1-type response. Several single nucleotide polymorphisms have been identified in the IL-12 gene such as 3′UTR 1188 A/C polymorphism, which is associated with different diseases. However, the relationship of this polymorphism with the immune response in leprosy has not been explored. In this case–control study, we evaluated 44 patients with lepromatous leprosy (LL) and 51 healthy subjects (HS). We aimed to determine the relationship between 3′UTR 1188 A/C polymorphism of IL-12 p40, mRNA expression, and soluble IL-12 concentration in LL patients and HS. Genotype frequencies were 41% A/A, 36% A/C, and 23% C/C in LL patients, and 47% A/A, 49% A/C, and 4% C/C in HS (p < 0.05). LL patients had a lower mRNA expression of IL-12 p40 gene, whereas HS had a higher expression level. Soluble IL-12 p40 concentration was higher in LL patients than in HS (p < 0.05). IL-12 p70 concentration did not differ between groups, and IL-12 p40 concentration was not significantly correlated with mRNA expression in either group. These data suggest that IL-12 p40 3′UTR 1188 A/C polymorphism is associated with greater susceptibility to lepromatous leprosy in patients from western Mexico, independently of IL-12 p40 and p70 expression levels.