Interestingly, the serum levels of IL-21 were found persistently elevated, from the 11th day after infection until the chronic phase (Fig. S7A) and qPCR analysis of SMCs revealed increased abundance of the IL21 transcript as early as day 11 pi (Fig. S7B), thus suggesting that additional populations may produce IL-21 in the early acute phase as well as in the chronic phase. This evidence concerns the gene IL21 and infection.