Epithelium in contact with microbial flora Systemic Immune Competence Lumen Mucus Layer <fIntermicrobial Interactions Mucosal epithelium Mucosal lymphoid tissue Lamina propria Figure by MIT oCW. Opportunistic Infection Normal Intestinal Ecosysten Infection with Overt Pathogen Figure by MIT oCW. MIT OCWEpithelium in contact with microbial flora Figure by MIT OCW. Figure by MIT OCW. Figures by MIT OCW