Proteolytic degradation of invasin in mouse small intestine. 5 Balb/c mice were infected orally with 109 CFU Y. enterocolitica WA-314 (wt) or an isogenic inv mutant (inv). Mice were sacrificed at the indicated time points and bacteria were washed from small intestinal lumen with PBS. For each lane 3 × 106 yersiniae were subjected to Western blotting with an a Inv polyclonal antibody. Solid arrowheads point to full length Inv, arrowheads point to specific Inv degradation products.