The MHC class II transactivator: prey and hunter in infectious diseases

The MHC class II transcriptional activator (CIITA) is the major regulator o f expression of MHC class If genes. Thus, CIITA plays a fundamental role in the regulation of the immune response. Here, we discuss our findings on th e dual role of CIITA during infections, as the target (prey) for certain pa thogens but the host effector (hunter) against other pathogens, including H IV-1. This dual role is placed in an evolutionary context as a rather pecul iar example of a strategy used by pathogens to evade host defenses and a co unteraction of the host to minimize the survival and spread of the pathogen .