The role of CD8 molecules in the recognition of antigens in association with MHC-I molecules is very important and since CD8 positive T cells can become infected in transit through a CD4/CD8 double positive state, it is possible that Nef-dependent CD8 down-regulation provides a mechanism to avoid antigen recognition and cytotoxic responses to pathogens, therefore playing an important role in the subversion of the immune system during HIV infection. The gene discussed is S100B; the disease is HIV infectious disease.