At day 12 after secondary challenge, splenocytes were cultured in vitro for 72 h and the supernatants were analyzed for TNF-α, IFN-γ, and granzyme B. As shown in Figure 6, the antigen specific TNF-α and IFN-γ responses followed a similar trend as in primary infection, but, as expected, much higher levels of cytokines were produced. Here, TNF is linked to infection.