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Immune System and Immunity

Explore the intricate workings of the immune system, from barriers like skin and mucous membranes to the specialized organs and cells like lymph nodes, macrophages, and lymphocytes. Discover the three lines of defense - from inflammation to antibody-mediated responses - and the crucial role of B and T cells in immunity. Learn how antibodies bind to antigens, forming a vital defense against pathogens. Unravel the concept of memory in infections, secondary immunity, and the importance of vaccination in bolstering immune responses against diseases.

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Immune System and Immunity

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  1. Immune System and Immunity Lymphatics,Barriers, General mechanisms and Immunity

  2. Organs of the lymph system • Bone marrow, lymph nodes, spleen, and thymus. • B-lymphocytes (B-cells) mature in the bone marrow. T-lymphocytes (T-cells) mature in the thymus gland. • Leukocytes are produced in the bonemarrow. • Lymph nodes are areas of concentrated lymphocytes and macrophages along the lymphatic veins.

  3. Immunity • Immunity is the body's capability to repel foreign substances and cells. • There are three lines of defence: • 1st Line - Barriers - skin and mucous membranes. The skin surface dry and pathogens are unable to penetrate its tough layers. Tears and saliva secrete enzymes that breakdown bacterial cell walls. Skin glands secrete chemicals. Mucus membranes lining the respiratory, digestive, urinary, and reproductive tracts secrete mucus that forms another barrier.

  4. Macrophages • Macrophages are white blood cells that continually search for foreign (nonself) antigenic molecules. • When found, the macrophages engulfs and destroys them. • Small fragments of the antigen are displayed on the outer surface of the macrophage plasma membrane.

  5. 2nd Line – The Inflammatory Response • Inflammation results when damaged cells release histamines (causing the areas to become heated and reddened). • This makes the environment unfavorable for microbes, promotes healing, raises mobility of white blood cells, and increases the metabolic rate of nearby cells. • Capillaries pass fluid into interstitial areas, causing the infected/injured area to swell. • The inflammatory response is often strong enough to stop viruses, bacteria, and fungi. • If this is not enough, the 3rd line must act

  6. 3rd Line Defence • The 3rd line directly kills microbes, supplements inflammatory response, and works with the immune response.

  7. Specific 3rd line Defenses • Immunity results from the production of antibodies specific to a given antigen. • Antibodies bind to the antigens on invaders and kill or inactivate them in several ways. • Most antibodies are themselves proteins or are a mix of protein and polysaccharides. • Antigens can be any molecule that causes an immune system response. There are two types: pathogens and allergens.

  8. Lymphocytes • Lymphocytes (B or T) circulate in the blood and are associated with the lymph nodes and spleen. • B cells remain in the bone marrow and develop before moving into the circulatory and lymph systems. • B cells stimulate plasma cells to produce antibodies. • Antibody-mediated immunity is regulated by B cells and the antibodies they produce.

  9. Antibody-mediated reactions defend against invading viruses and bacteria. • Cell-mediated immunity concerns cells in the body that have been infected. • Stages in this process are: • 1.antigen detection • 2.activation of helper T cells • 3.antibody production by B cells

  10. Helper T Cells • Helper T cells become activated when they encounter the antigens now displayed on the macrophage surface. • Activated T and activated B cells also identify.

  11. B - cells • B cells divide, forming plasma cells and B memory cells. Plasma cells make and release between 2000 and 20,000 antibody molecules per second into the blood for the next four or five days. • B memory cells live for months or years, and are part of the immune memory system.

  12. T-Cells • T-cells with the help of helper T’s make memory T’s and killer T’s primarily to fight viral antigens. • These cells attack infected cells and destroy them • Suppressor T’s are required to suppress them after an infection is cured

  13. Antibodies • Antibodies bind to specific antigens in a lock-and-key fashion, forming an antigen-antibody complex. • Antibodies are a type of protein molecule known as immunoglobulins. • Function of antibodies includes: • 1.Recognition and binding to antigens • 2.Inactivation of the antigen

  14. Memory of infections • Secondary immunity, the resistance to certain diseases after having had them once, results from production of Memory B and T cells during the first exposure to the antigen. • A second exposure to the same antigen produces a more massive and faster response. • The secondary response is the basis for vaccination.

  15. Memory of infections • Vaccination is a term derived from the Latin vacca (cow, after the cowpox material used by Jenner in the first vaccination). • A vaccine stimulates the antibody production and formation of memory cells without causing of the disease. • Vaccines are made from killed pathogens or weakened strains that cause antibody production but not the disease.

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