Leprosy,a chronic infectious disease, continues to remain an important health problem in developing countries including India. The susceptibility to leprosy involves strong host genetic components inherited at birth. In a replicative case-control study from India, we identified the genetic variant in a pro-inflammatory IL12B cytokine gene subunit with a strong association with leprosy susceptibility, probably by affecting the binding of splicing factor(s). Gene-gene interaction analysis at multiple risk loci highlighted the importance of specific genetic backgrounds of immune response related genes in the outcome of M. leprae infection. Further a preliminary study, using a subset of samples, showed the increase in copy number of IL23R gene associated with pauci-bacillary form of leprosy which correlated with a trend towards enhanced expression in memory T cells. (By Prof. R.N.K.Bamezai, http://jmg.bmj.com/content/50/1/34 )