Normal GI tract physiology

Intestinal immunity represents the largest and most complex portion of the immune system.1 For appropriate gut immune responses, it is important for the intestinal immune system to distinguish between invasive organisms and harmless antigens.1

  • The intestinal barrier is composed of a thick secreted mucus layer, an epithelial layer and the underlying nonepithelial mucosal cells (eg, lymphocytes)2
  • The lamina propria contains various immune cells such as antibody-secreting IgA plasma cells, macrophages, dendritic cells, and T cells.3
Normal tract
  1. Mowat AM. Anatomical basis of tolerance and immunity to intestinal antigens. Nat Rev Immunol. 2003;3(4):331-341.

  2. McGuckin MA, Eri R, Simms LA, Florin TH, Radford-Smith G. Intestinal barrier dysfunction in inflammatory bowel diseases. Inflamm Bowel Dis. 2009;15(1):100-113.

  3. Adams DH, Eksteen B, Curbishley SM. Immunology of the gut and liver: a love/hate relationship. Gut. 2008;57(6):838-848.

  4. Stedman’s Medical Dictionary. 27th ed. New York, NY: Lippincott Williams & Wilkins; 2000.

  5. Janeway CA Jr, Travers P, Walport M, Shlomchik MJ. Immunobiology: The Immune System in Health and Disease. 6th ed. New York, NY: Garland Science Publishing; 2005.

  • Antigen: any molecule that can bind specifically to an antibody5

  • Lamina propria: the layer of connective tissue underlying the epithelium of a mucous membrane4

  • Plasma cells: terminally differentiated B lymphocytes, which are the main antibody-secreting cells of the body5

  • Macrophages: large, migratory, mononuclear phagocytic cells important in innate immunity and in early nonadaptive phases of host defense; act as antigen-presenting cells and as effector cells in humoral and cell-mediated immunity5

  • Dendritic cell: specialized to take up antigen, process it, and display it for recognition by T lymphocytes5

  • T cell: a subset of lymphocytes defined by their development in the thymus and by heterodimeric receptors associated with the proteins of the CD3 complex5

Back to front page