12.6 Short Answer: Large amounts of IgA are produced by intestinal B cells and plasma cells and secreted into the lumen as a means to keep the microbiota in check and prevent invasion from pathogens, yet most individuals with IgA deficiency are not overly susceptible to infections. Explain why this is the case.
12.7 Multiple Choice: Which of the following best describes intraepithelial lymphocytes (IELs)?
A. Express CCR9 and α4β7 integrin B. Express CCR9 and αEβ7 integrin (CD103)
C. Have a CD4 to CD8 T cell ratio of 3:1
D. Contain CD4+ T cells that produce IFN‑γ, IL‑17, and IL‑22
E. Consist of 90% T cells, 80% of which express CD8 as an α:α homodimer or an α:β heterodimer
F. A and C
G. B and E
H. A, C, and D 12.8 Multiple Choice: Which of the following cell types depend on aryl hydrocarbon receptor expression for proper development?
A. Type b intraepithelial lymphocyte (EIL) B. ILC1
C. B cell
D. Macrophage E. ILC2
F. Neutrophil 12.9 Matching: Match the human disease with the
C. Antibiotic treatment that eliminates iii. Inflammatory the bulk of commensal flora allowing bowel disease a particular species to overgrow and (Crohn’s produce toxins that lead to severe disease and diarrhea and mucosal injury ulcerative colitis)
D. Hyperactive immune responses to iv. Diversion colitis commensal bacteria due to defects in innate immunity genes 12.10 True or False: Lamina propria CD4+ T cells secrete large amounts of cytokines such as IFN‑γ, IL‑17, and IL‑22 only in response to pathogens and inflammatory insults.
12.11 True or False: Most Tregs in the small intestine do not express FoxP3.
General references.
Hooper, L.V., Littman, D.R., and Macpherson, A.J.: Interactions between the microbiota and the immune system. Science 2012, 336:1268–1273.
MacDonald, T.T., Monteleone, I., Fantini, M.C., and Monteleone, G.: Regulation of homeostasis and inflammation in the intestine. Gastroenterology 2011, 140: 1768–1775.
Mowat, A.M.: Anatomical basis of tolerance and immunity to intestinal antigens. Nat. Rev. Immunol. 2003, 3:331–341.
Society for Mucosal Immunology: Principles of Mucosal Immunology, 1st ed. New York, Garland Science, 2013.
Section references.
12-1 The mucosal immune system protects the internal surfaces of the body.
Brandtzaeg, P.: Function of mucosa-associated lymphoid tissue in antibody formation. Immunol. Invest. 2010, 39:303–355.
Cerutti, A., Chen, K., and Chorny, A.: Immunoglobulin responses at the mucosal interface. Annu. Rev. Immunol. 2011, 29:273–293.
Corthesy, B.: Role of secretory IgA in infection and maintenance of homeostasis. Autoimmun. Rev. 2013, 12:661–665.