page_title: Gut-specific homing
section_title: T cell summary
hierarchical_section_title: Gut-specific homing / T cell summary
caption_attribution_description: English: 3D illustration of a lymphocye cell
context_page_description: Gut-specific homing is the mechanism by which activated T cells and antibody-secreting cells are targeted to both inflamed and non-inflamed regions of the gut in order to provide an effective immune response. This process relies on the key interaction between the integrin α4β7 and the addressin MadCAM-1 on the surfaces of the appropriate cells. Additionally, this interaction is strengthened by the presence of CCR9, a chemokine receptor, which interacts with TECK. Vitamin A-derived retinoic acid regulates the expression of these cell surface proteins.
context_section_description: T cells are produced in the thymus, and upon leaving they migrate to and around the lymphoid organs of the body, including lymph nodes. In the paracortex of the lymphoid nodes they are exposed to professional antigen-presenting cells (APCs), such as dendritic cells (DCs). Specific interactions between the naïve T cells and their cognate antigens result in T cell activation. The activated T cells, immunoblasts, undergo clonal expansion before acquiring effector functions. The activated T cells then emigrate from the lymph nodes, via the efferent lymphatic vessel, and migrate around the body in the blood.
  In certain circumstances, some activated T cells show a preference for patrolling certain tissues. This has been termed lymphocyte homing. Gut-specific homing is the preferential movement of activated T cells to the intestine and the gut. In this way T cells are effectively recruited to form part of the first line of defense against pathogens. This is because T cells are targeted to and recirculated around primary infection sites. Overall this results in an extremely high concentration of lymphocytes in this region; 70% of the immunoglobulin-producing cells are found in the mucosal surfaces of the body.
caption: T cell image
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