Immunohistochemical staining and reverse transcription–polymerase chain reaction (RT-PCR) analysis for Muc2 (Figure 1B and C) showed that significantly higher amounts of Muc2 were expressed within the cecal crypts of the resistant mice on day 21 after infection than in the naïve and susceptible mice; a similar staining pattern was observed with the PAS reagent (Supplementary Figure 1). This evidence concerns the gene MUC2 and infection.