Association between tuberculosis and a polymorphic NFkappaB binding site in the interferon gamma gene.

Interferon gamma is believed to be crucial for host defence against many infections. To test the hypothesis that a polymorphism in the gene for interferon gamma (IFNG) is associated with susceptibility to tuberculosis, we did two independent investigations. In a case-control study of 313 tuberculosis cases, we noted a significant association between a polymorphism (+874A-->T) in IFNG and tuberculosis in a South African population (p=0.0055). This finding was replicated in a family-based study, in which the transmission disequilibrium test was used in 131 families (p=0.005). The transcription factor NFkappaB binds preferentially to the +874T allele, which is over-represented in controls. This preferential binding suggests that genetically determined variability in interferon gamma and expression might be important for the development of tuberculosis.