26 1 Organs Tissues and Cells of the Immune System The immune system protects the body by fighting infection and cancer The immune systems consists of several lymphatic organs Red bone marrow Thymus gland Lymph nodes Spleen 26 1 Organs Tissues and Cells of the Immune System cont There are also specialized lymphatic tissues Tonsils Appendix Specialized cells also contribute to the immune system 26 1 Organs Tissues and Cells of the Immune System cont 26 1 Organs Tissues and Cells of the Immune System cont 26 1 Organs Tissues and Cells of the Immune System cont Lymphatic Organs These various organs tissues and cells provide for immunity which is the ability to react to antigens Antigens are proteins that are foreign to the organism Each lymphatic organ has a specific function in immunity All lymphatic organs contains one or more lymphocytes one category of immunocells that protect the body Antibodies are specialized proteins produced by an organism that bind to specific antigens 1 Red Bone Marrow Thymus Gland The red bone marrow produces all the different types of red blood cells Immature T cells produced by the red bone marrow migrate to the thymus where they complete their maturation There are several types of lymphocytes produced by the red bone marrow B lymphocytes also called B cells T lymphocytes also called T cells The thymus produces hormones that are thought to help T cells mature Lymph Nodes The lymph nodes filter the lymphatic fluid to remove antigens and pathogens Antigens and pathogens are removed by the phagocytic macrophages Lymphocytes in the lymph nodes all contribute to the defense against antigens and pathogens in the lymphatic fluid 26 2 Nonspecific Defenses The body has a variety of nonspecific defenses that help protect the body from infection Barriers to entry The inflammatory response Natural killer cells The thymus selectively release T cells that have matured properly Spleen The spleen has two areas that contribute to immunity Red pulp White pulp The red pulp filters pathogens and debris with the help of macrophages The white pulp contains lymphocytes that fight pathogens and cancer Barriers to Entry There are two primary barriers that prevent entry of pathogens into the body The skin The mucous membranes In addition to mechanically blocking pathogen entry the skin has oil glands secrete chemicals to counter pathogens 2 Barriers to Entry cont The Inflammatory Response Any damage to the body s tissues trigger events of the inflammatory response Reddening An increase in temperature Swelling Pain The inflammatory response also involves three cell types Mast cells Neutrophils Macrophages The Inflammatory Response cont The Inflammatory Response cont The mast cells release chemicals such as histamine to increase the blood flow through the capillaries Neutrophils are phagocytic white blood cells that migrate to the site of injury This increased blood flow contributes to the redness swelling and warmth Macrophages have several roles These cells are phagocytic These cells release chemicals that trigger white blood cell production in the red marrow Because of the swelling nerve receptors are triggered to create the sensation of pain The Inflammatory Response cont The Inflammatory Response cont 3 The Complement System The Complement System cont The complement system consists of a variety of blood plasma proteins When activated by the presence of pathogens these proteins amplify the immune response Complement proteins also form a membrane attack complex that contributes to the lysis of pathogens Natural Killer Cells 26 3 Specific Defenses Natural killer cells are non specific lymphocytes that kill virus infected and cancerous cells Specific defenses are used in immunity when the nonspecific defenses fail to halt a pathogen or infection Natural killer cells kills cells that lack surface proteins identifying them as self One advantage of the specific defenses is that they can provide a memory of the infection B Cells and the Antibody Response B Cells and the Antibody Response cont The B cell receptor BCR on the surface of B cells allows for the recognition of and binding to specific antigens Plasma cells are responsible for the mass production of antibodies for the antigen The binding of the BCR to an antigen activates the B cell The antibodies are released into the bloodstream to help the body identify the antigen within the body Activated B cells undergo cell division to produce two special types of B cells Plasma B cells Memory B cells 4 B Cells and the Antibody Response cont B Cells and the Antibody Response cont Memory B cells are retained within the body for an extended period of time The memory B cells allow the body to mount an immune response more quickly if the antigen is perceived again B Cells and the Antibody Response cont The Function of Antibodies Recall that antibodies are immunoglobulin proteins that recognize specific antigens and forms an antibody antigen complex The formation of an antibody antigen complex can mark an antigen for destruction by neutrophils or macrophages The antibody antigen complex may also act as complement to amplify the immune response The Function of Antibodies cont The Function of Antibodies cont The proteins that determine blood type are also a type of antigen on the surface of red blood cells Type A B or AB blood results from the presence of the A and or B antigen Type O blood occurs when the red blood cells lack the A or B antigen 5 The Function of Antibodies cont The Function of Antibodies cont The blood also contains antibodies to the red blood cell antigens that are not present If incompatible types of blood are mixed antibody antigen complexes can form when agglutination occurs This clumping of red blood cells restricts blood flow and can ultimately be fatal T Cells and the Cellular Response The mature T cells that leave the thymus gland have unique T cell receptors TCR These receptors only recognize an antigen when an antigenpresenting complex APC of a macrophage presents the antigen to the TCR T Cells and the Cellular Response cont An activated T cell undergoes cell division to produce two types of T cells Cytotoxic T cells Helper T cells The presentation of the antigen by the APC activates the T cell T Cells and the Cellular Response cont Types of T Cells Cytotoxic T cells release a protein called perforin to create a pore in the surface of infected cells Cytotoxic T cells also release granzymes that then trigger the