1 Introduction.- 1.1 Intestinal Mucins.- 1.2 The Mucosal Immune System.- 1.3 Objectives and Scope of the Research Presented in This Monograph.- 2 Materials and Methods.- 2.1 Animals.- 2.2 Diets.- 2.3 Preparation of Tissues and Histochemical Methods.- 2.4 Quantitative Morphology.- 2.5 Morphometry.- 2.6 Lectin Histochemistry to Identify Carbohydrate Residues of Mucin.- 2.7 Staining Procedure for Neuroendocrine Cells.- 2.8 Syngeneic Bone Marrow Transplantation.- 2.9 Human and Mice Peyer's Patches.- 3 Mucosal Responses to Diet and Flora.- 3.1 Progress in Research of Intestinal Mucins.- 3.2 Results and Discussion.- 4 Influence of Diet and Microflora on Distribution of Enteroendocrine Cells.- 4.1 Results.- 4.2 Discussion.- 5 Peyer's Patches of SCID Mice After Syngeneic Normal Bone Marrow Transplantation.- 5.1 Results.- 5.2 Discussion.- 6 Carbohydrate Expression in Human and Mouse Peyer's Patches.- 6.1 Results.- 6.2 Discussion.- 7 General Discussion and Conclusions.- 7.1 Summary.- References.