OBJECTIVES. The Amazing Immune System

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1 The Amazing Immune System Graphic source: (l) Jeanne Kelly, NIAID; (r) Wikimedia Commons OBJECTIVES Describe at least three components of the immune system Describe the role in our immune response of at least 3 components of the immune system

2 No financial conflict of interest to disclose. The Immune System Complex system of organs and cells Essential function: differentiate self from non-self Protects body from external (e.g. infections, toxins) and internal (e.g. cancer) challenges Four Primary Functions Recognition of self self-tolerance immunological privilege (protects fetus) Immunosurveillance Patrols for cancer cells Intracellular hormones Chemical messengers Defense against infection Cells Antibodies

3 Organs of the Immune System Complex of lymphoid organs highly specialized cells General Groupings of Lymphoid Tissue Mucosal-Associated Lymphoid Tissue (MALT) Below mucous membranes of GI/respiratory tracts, thyroid, breast, lung, salivary glands, eye and skin Cutaneous-Associated Lymphoid Tissue (CALT) Epidermis with keratinocytes and Langerhans cells Bronchous-Associated Lymphoid Tissue (BALT) Peribronchial, perivascular, and interstitial areas of the lungs Gut-Associated Lymphoid Tissue (GALT) Tonsils, adenoids, esophagus, stomach, Peyers patches, large intestine, appendix, lamina propria 60-70% of the immune system Nasal-Associated Lymphoid Tissue (NALT) Lymphoid structures similar to Peyers Patches but found in the nasal mucosa Organs of the Immune System Adenoids single clump of spongy tissue 1 st line to stop infectious organisms nasally Shrinks by teenage years; absent in adults Tonsils 1 st line to stop infectious organisms orally Mature by teenage years; less functional as we age Source of antibodies and lymphocytes

4 Organs of the Immune System Thymus anterior mediastinum (upper chest) above the heart Flat bi-lobed gland Largest just prior to birth and atrophies with age Produce mature T-cells from the immature cells produced by the bone marrow during childhood Eliminates detrimental T- cells Organs of the Immune System Thoracic duct (left lymphatic duct), largest lymphatic vessel, empties into left subclavian vein Right lymphatic duct empties into the right subclavian vein and/or right internal jugular Semilunar valves prevent blood back flow Organs of the Immune System Lymph Nodes Encapsulated beanshaped structures One of the most highly organized lymphoid organs T-cell and B-cell activity Site where immune response is mounted Lymphs, macrophages and dendritic cells (messenger cells) Source: en.wikipedia.org

5 Organs of the Immune System Spleen One of the most highly organized lymphoid organs Large, ovoid Not supplied by lymphatic vessels Major role in mounting immune response to antigens in the bloodstream Splenic Artery 2 types of compartments: Red pulp macrophages & red blood cells White pulp T-cells Organs of the Immune System Lamina Propria Under the epithelial layer of all mucous membranes Contains B-cells, plasma cells, activated T-helper cells & macrophages Peyer s Patches Under the lamina propria In the ileum About 30 are found in humans T- & B-lymphocytes Important in immunosurveillance Immune response within mucosa Organs of the Immune System Large Intestine Probiotics very important Trains immune system Important in young children up to age 7 Appendix Lymphoid tissue accumulates shortly after birth Peaks in second/third decades of life Disappearing after age 60 Maturation of B-cells IgA production Reservoir of good bacteria Direct responses in other areas of the body

6 Organs of the Immune System Bone Marrow Yellow-white tissue in the middle of many bones Originates ALL cells of immune system B-cell origin and development Eliminates bad B-cells Also produces natural killer (NK) cells, granulocytes, immature thymocytes, red blood cells and platelets Other precursors migrate to other areas to mature Innate vs. Adaptive Immune System Innate immune system Adaptive (acquired) immune system Table source: Wikipedia Mechanism of Antibody Production Macrophage attracted to/ingests foreign antigen Antigenic proteins cleaved; fragments appear on surface of macrophage T cell sees macrophage with antigenic protein on surface and stimulates B cell Stimulated B cell divides and makes plasma cells; plasma cells make antibodies Takes approx. 3 weeks after exposure for detectable antibodies to appear in the blood Single neutrophil (yellow), engulfing anthrax bacteria (orange) Photo source: Wikimedia

7 Antibody Production Antigen Antigen presentation T cell Macrophage Message Antibodies Plasma cell B cell This is an example of what type of immunity? Source: CDC. Module 3: Targeted Testing and the Diagnosis of Latent TB Infection and TB Disease s/default.htm Phagocytes in Action See a video of a phagocyte engulfing Aspergillus and Candid conidia: Polymorphonuclear_Cells_with_Conidia_in_Liquid_Media.o gg See a video of a WBC chasing bacteria at er_embedded

8 Do you know your cells? 1. Pus is comprised mostly of what cells? 2. These cells are involved in allergic reactions and may be seen in increased numbers in a CBC. 3. These cells play a major role in orchestrating the overall immune system. 4. What cells would you expect to see in increased numbers in a patient that has a hookworm infection? Knowledge check 1. A primary immune response in an adult requires approximately how much time to produce detectable antibody levels in the blood? A. 12 hours B. 3 days C. 1 week D. 3 weeks TYPES OF ANTIBODIES Source: National Cancer Institute, NIH IgM current disease; first at site of initial exposure there to Mop up the infection IgG first with subsequent exposure I Got it and it s Gone IgA secreted on mucous membranes IgE allergic reactions IgD secreted in small amounts by surface of B- lymphocytes to signal other cells

9 Knowledge Check A patient with a temperature of 40ºC, a rash, and no history of measles immunization has the following lab results on a blood specimen collected 4 days after onset of rash: IgM positive and IgG negative Unfortunately, no convalescent blood sample was collected. Is this rash likely to be measles? CDC: Do You Know? What are the 5 cardinal signs of inflammation? The traditional names for signs of inflammation come from Latin: Dolor (pain) Calor (heat) Rubor (redness) Turgor (swelling) Functio laesa (loss of function) Summary The immune system is a complex network of cells, tissues and organs that work together to defend the body against attacks by foreign invaders When the immune system hits the wrong target or is crippled, it can unleash a torrent of diseases, including allergy, arthritis, and AIDS

10 References Craig CG. Microbial Pathogenicity and Host Response. In: Chapter 14. APIC Text of Infection Control and Epidemiology, 3 rd ed. National Cancer Institute. The Immune System cancer/immunesystem National Institute of Allergy and Infectious Diseases. The Immune System ges/default.aspx