To examine whether simultaneous infection of two pathogens results in analogous pathogen-specific imprinting or unique imprinting, co-infection studies were performed with LCMV Armstrong and MCMV-GP33, and the differentiation of the GP33-specific CD8+ T cells, which are able to respond to both viruses in the same host, was compared with single infection (Figure 5A). Here, CD8A is linked to coinfection.