Studies in humans on the kinetics of antibody production directly after M. leprae infection, including quantitative and qualitative differences between IgM and IgG, have been considerably constrained due to the facts that anti-PGL-I immunity cannot discriminate between past and present M. leprae infection (Pierneef et al., 2021), most humans do not develop disease after M. leprae infection and leprosy has a long incubation time (Scollard et al., 2006). Here, CD40LG is linked to leprosy.