© 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey Chapter 24 The Immune System

Function of the Immune System  Prevent pathogens from entering  Eliminate pathogens from body  Provide memory against future infections from same pathogen –Pathogen = agent that causes disease © 2012 Pearson Education, Inc.

2 Divisions of Immune System  INNATE (Non-specific) –1st line of defense; general response –Quick to respond –Prevent than eliminate –Same response whether or not pathogen encountered before © 2012 Pearson Education, Inc.

2 Divisions of Immune System  ADAPTIVE (Specific) –Recognizes specific pathogens –Slower to respond (1st time) –Responsible for immune system memory –Previous exposure to pathogen enhances immune response © 2012 Pearson Education, Inc.

INNATE IMMUNITY © 2012 Pearson Education, Inc.

Figure 24.1A Innate immunity (24.1–3) The response is the same whether or not the pathogen has been previously encountered Adaptive immunity (24.4–15) Found only in vertebrates; previous exposure to the pathogen enhances the immune response External barriers (24.1) Internal defenses (24.1–2) The lymphatic system (24.3) Antibodies (24.8–10) Lymphocytes (24.11–13) Phagocytic cells NK cells Defensive proteins Inflammatory response (24.2) Skin/ exoskeleton Acidic environment Secretions Mucous membranes Hairs Cilia

Some Components of Innate immunity  Phagocytic cells –Neutrophils and macrophages, –large cells that wander through the interstitial fluid and blood –Destroy bacteria and virally-infected cells  natural killer cells that attack cancer cells and virus- infected cells  complement system, a group of proteins that recruit other immune responses  Inflammation and Histamine © 2012 Pearson Education, Inc.

Figure 24.2_1 Tissue injury; signaling molecules, such as histamine, are released. Blood vessel White blood cell Signaling molecules Bacteria PinSkin surface 1

Figure 24.2_2 2 Dilation and increased leakiness of local blood vessels; phagocytes migrate to the area. Swelling Blood clot Phagocytes and fluid move into the area

Figure 24.2_3 3 Phagocytes (macrophages and neutrophils) consume bacteria and cellular debris; the tissue heals. Phagocytes

Lymphatic System Function  Return tissue fluid back to CV system  Fight infection –As lymph circulates through lymphatic organs it collects pathogens –transports them to lymphatic organs –Here, macrophages engulf the invaders and –lymphocytes may mount an adaptive immune response. © 2012 Pearson Education, Inc.

Figure 24.3 Lymphatic capillary Interstitial fluid Tissue cells Blood capillary Lymphatic vessel Valve Masses of lymphocytes and macrophages Lymph node Lymphatic ducts that drain into veins Lymphatic vessels Bone marrow Appendix Spleen Thymus Lymph nodes Tonsils Adenoid Organs

ADAPTIVE IMMUNITY © 2012 Pearson Education, Inc.

24.4 The adaptive immune response counters specific invaders  Our immune system responds to foreign molecules called antigens  Antigens –are molecules that elicit the adaptive immune response, –Example: proteins or large polysaccharides on the surfaces of viruses or foreign cells  The adaptive immune system –reacts to specific pathogens –“remembers” an invader. © 2012 Pearson Education, Inc.

24.5 Lymphocytes mount a dual defense  Lymphocytes –are responsible for adaptive immunity, and –originate from stem cells in the bone marrow. –B lymphocytes or B cells continue developing in bone marrow. –T lymphocytes or T cells develop further in the thymus. © 2012 Pearson Education, Inc.

Figure 24.5A Bone marrow Stem cell Immature lymphocytes Via blood Antigen receptors Thymus T cell B cell Via blood Final maturation of B and T cells in a lymphatic organ Lymph nodes, spleen, and other lymphatic organs Humoral immune response Cell-mediated immune response

24.5 Lymphocytes mount a dual defense  B cells –participate in the humoral immune response –Acts on extracellular pathogens (pathogens in body fluids) –secrete antibodies to mark pathogen for destruction.  T cells –participate in the cell-mediated immune response, –Acts on bacterial or virally infected body cells; cancerous cells –promote phagocytosis by other white blood cells and stimulating B cells to produce antibodies. © 2012 Pearson Education, Inc.

24.5 Lymphocytes mount a dual defense  Millions of distinct B and T cells –each with different antigen receptors, capable of binding one specific type of antigen, –Antibodies = antigen receptors of B cells –T cell receptors = antigen receptors of T cells  Antigenic determinants are specific regions on an antigen where antibodies bind. –An antigen usually has several different determinants. © 2012 Pearson Education, Inc.

Figure 24.6 Two different antibody molecules Antigen- binding site Antigen molecule Antigenic determinant