DEFA5 and infection: Given that Ptpn2∆IEC mice exhibited higher mAIECred bacterial load in distal colon tissue, and our previous observations that whole-body constitutive Ptpn2-KO mice have reduced antimicrobial peptide (AMP) production and numbers of Paneth cells, we next investigated if the increased susceptibility of Ptpn2∆IEC mice to mAIECred infection involved altered host antimicrobial peptide defenses.32 Ileal IEC-mRNA expression of the α-defensins (Defa5 and Defa6), was significantly lower in Ptpn2∆IEC vs. Ptpn2fl/fl mice, after mAIECred but not K12 infection (Figure 4(A,B)).