In a study published in Molecular Ecology (http://doi.org/10.1111/mec.17534), Joanna Różańska-Wróbel, Jacek Radwan and their collaborators demonstrate that Major Histocompatibility (MHC) alleles predict production of antibodies against specific variants of OspC, a protein used by Borrelia to manipulate host immunity. The results provide an example of an interaction between immunity and infectivity genes predicted by the theory of host-parasite coevolution.