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Secondary (2 o ) Lymphoid Tissues

Secondary (2 o ) Lymphoid Tissues. Adapted from Roitt’s Immunology 7-1. What happens in 2 o lymphoid tissues?. Highly efficient in trapping and concentrating foreign substances carried in the blood and lymph

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Secondary (2 o ) Lymphoid Tissues

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  1. Secondary (2o) Lymphoid Tissues Adapted from Roitt’s Immunology 7-1

  2. What happens in 2o lymphoid tissues? • Highly efficient in trapping and concentrating foreign substances carried in the blood and lymph • They are the main sites of production of _antibodies_ and induction of antigen-specific T cells Why is that important? In a naïve (non-immunized) animal, only 1 in a 1,000 to 1 in 100,000 lymphocytes can recognize the typical foreign invader

  3. Lymph Nodes -The lymph node has specific region for bothT cells (Paracortex) andB cells (Follicle). -Lymphocytesenter the nodevia the bloodwhileantigensenter via the lymph vessels. -Both cell types encounter and respond to antigens in their respective zones. Abbas & Lichtman’s Basic Immunology 1-14 & 1-16

  4. Lymph Nodes Native T cells migrate into the lymph node via the bloodstream and become activated by antigens. The activated T cells exit the nodes via both the bloodstream and the lymph system where they can migrate to peripheral sites of infection. Abbas & Lichtman’s Basic Immunology 1-17

  5. Lymph Nodes • Lymph fluid • Lymph fluid from tissues drains into regional lymph nodes. • APC • APC in the lymph nodes can sample microbial antigens from the lymph fluid. Roitt’s Immunology 7-3

  6. Lymphocyte Recirculation • Naïve lymphocytes • Migrate from lymph node to lymph node looking for an APC to present the correct antigen to it. • Effector lymphocytes • Migrate to the site of infection (T cell) • Secrete antibody from lymphoid organ (B cell) • 80% of lymphocytes migrate to a different lymph node each day Abbas & Lichtman’s Basic Immunology 1-17

  7. Spleen • The T cellsare segregated to theperiarteriolar lymphoid sheath (PALS) • The B cellsare segregated to thesecondary follicle • Same role for blood-borne antigen as lymph node does for lymph-borne antigen. Abbas & Lichtman’s Basic Immunology 1-15

  8. Mucosa-associated Lymphoid Tissue (MALT) • Mucous - acts to trap microorganisms, allowing them to be swept away by ciliated epithelial cells towards external openings • Loose lymphoid aggregates that line mucosal epithelium • Non-encapsulated lymphoid tissues (as opposed to spleen and lymph nodes) • Cells of the MALT tend to recirculate only to other mucosal tissues • Typically found in the GI system where it is termed GALT (Gut-associated Lymphoid Tissue)

  9. Tissues of the Immune System Adapted from Sherwood’s Human Physiology Table 12-1

  10. Next Time • Describe the innate immune system. • Compare and contrast the innate immune system with the adaptive immune system. • Readings: Abbas & Lichtman, Chapters 1 & 2

  11. Objectives • Describe the normal functions of the immune system. • Describe the cells and tissues of the immune system. • Describe the maturation process of lymphocytes.

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