Chapter 35 The Bodys Defenses 35.1 The Lymphatic System l plasma leaves the blood at capillaries carries food and picks up waste this fluid fills space between cellscalled interstitial fluid needs to be returned to the blood l lymph system is a series of tubes (lymphatic vessels) that return interstitial fluid to the blood fluid in lymph vessels is called lymph plasma, interstitial fluid, and lymph are the same juice, different place Human Lymphatic System The bodys defenses 35.2 Nonspecific and Specific Defenses Nonspecific defenses occur automatically and have no memory l 1. barriers to entry skin mucous membranes secretions (oil, lysozyme, acid in stomach) l 2. inflammatory response: caused by physical or chemical damage or pathogens outward signs (from capillary changes) redness heat swelling pain Cilia in trachea 35.2 Nonspecific and Specific Defenses l 2. inflammatory response, cont. helps prevent spread of infection can inhibit healing if skin is not broken (ice, ibuprofen, cortisone) triggered by damaged tissue cells and mast cells (WBCs in connective tissues) releasing histamine results in dilation of vessels increased permeability also triggers fever inhibitis microbes helps in tissue repair facilitates phagocytes faster immune cell division Fig Inflammatory response Inflammatory response 35.2 Nonspecific and Specific Defenses l 3. phagocytes and natural killer cells phagocytes neutrophils and monocytes: amoeboid, squeeze through capillaries monocytes become macrophages dendritic cells (in skin, mucous membranes) and macrophages (other tissues) recognize pathogens with receptors devour pathogens release cytokines to stimulate neutrophils and monocytes move through tissue fluid lymph spleen and activate B and T cells Phagocytosis 35.2 Nonspecific and Specific Defenses l 3. phagocytes and natural killer cells natural killer cells (NK) large, granular kill infected (viral) and cancerous body cells by cell-cell contact kill cells without self-proteins; same manner as cytotoxic T cells 35.2 Nonspecific and Specific Defenses l 4. protective proteins complement (blood plasma proteins) amplify inflammatory response can bind to pathogens with antibodies, ensuring phagocytosis can form membrane attack complex; holes cause lysis interferons produced by virus-infected cells to warn others cause production of substances that interfere with viral replication in non-infected cells 35.2 Nonspecific and Specific Defenses Specific defenses require B-cells and T-cells l two major cell types: B cell lymphocytes chemical immunity, kill germs using chemicals (antibodies) made in Bone marrow T cells lymphocytes helper T: control immune system (T H ) cytotoxic T: kills germs (T C ) suppresser T: stops immune system when the attack is over (T S ) made in Thymus 35.2 Nonspecific and Specific Defenses l two major cell types, cont. lymphocytes respond to antigens antigen (antibody generating): foreign molecule (protein) that elicits a response by lymphocytes may belong to viruses, bacteria, fungi, protozoa, parasitic worms, pollen, transplanted tissue, etc. stimulate production of antibodies, which bind to antigens B cells and T cells undergo clonal selection there are millions of types of lymphocytes, each with unique membrane receptors specific for various antigenic molecules Clonal selection 35.2 Nonspecific and Specific Defenses l two major cell types, cont. B cells and T cells undergo clonal selection when an antigen is encountered for the first time, the lymphocyte attaches to the receptor complementary to it cell with the receptor produces clones of itself; clones become: effector cells (plasma cells)attack the antigen (primary immune response (takes days)) memory cells (last a lifetime)quickly attack antigen on 2nd (and later) exposures (secondary immune response, AKA immunity) 35.2 Nonspecific and Specific Defenses l two major cell types, cont. lymphocytes work by recognizing each other, invaders, and other body cells with proteins on their membranes major histocompatibility complex (MHC) Class I MHC: on all body cells, identifies cells as being part of the body Class II MHC: only on immune cells antigens attach to MHC proteins B cells have antigen-specific receptors (similar to antibodies) on their membranes T cells have T cell receptors on theirs both types of receptors are complementary to a specific antigen/MHC Interaction of T cells with MHC molecules Specific defenses flow chart 35.2 Nonspecific and Specific Defenses l helper T cells (T H ) immature T H becomes a mature T H T H divides producing clones and memory T H stimulate B and T C Role of helper T cells 35.2 Nonspecific and Specific Defenses l role of T H cells macrophage surrounds and engulfs antigen macrophage begins to process the antigen processed antigen will be attached to Class II MHC 35.2 Nonspecific and Specific Defenses l role of T H cells, cont. processed antigen on the macrophage is complementary to T H receptor T H and macrophage bind interleukins are released by the macrophage which causes T H to mature 35.2 Nonspecific and Specific Defenses l cell-mediated immunity uses cells (T C ) to kill eukaryotic cells, including: protists and fungi, virus-infected cells, cancer cells steps (for instance): antigen enters a body cell and is processed after being processed, the antigen is displayed on a Class I MHC 35.2 Nonspecific and Specific Defenses l cell-mediated immunity steps, cont. immature cytotoxic T cell binds with macrophage displaying antigen mature helper T-cell attaches to Class II MHC on macrophage and pumps out interleukins 35.2 Nonspecific and Specific Defenses l cell-mediated immunity steps, cont. interleukins cause cytotoxic T cell to mature mature T C binds to infected cell and pumps out perforin to kill it Perforin 35.2 Nonspecific and Specific Defenses l antibody-mediated immunity kills bacteria and viruses with antibodies antibodies: cause germs to stick together or precipitate, easier for macrophages to eat inactivate germ (block virus attachment) work with the complement proteins to kill the germ are made by B cell lymphocytes Antibody activity 35.2 Nonspecific and Specific Defenses l antibody-mediated immunity steps: a specific B cell binds to an antigen (such as a virus) by its receptor antigen is engulfed antigen is processed and the processed antigen is displayed on the Class II MHC 35.2 Nonspecific and Specific Defenses l antibody-mediated immunity steps, cont. B cell is now activated and finds a mature helper T cell, usually at a lymph node or other lymphatic tissue helper T cell releases interleukins which cause B cell to divide 35.2 Nonspecific and Specific Defenses l antibody-mediated immunity steps, cont. new B cells are called plasma cells which mass produce antibodies (30,000 molecules/second!) some B cells become memory cells which wait until next infection (source of immunity) Immunological memory AIDS l human immunodeficiency virus attacks helper T cells l antibodies are made, but are ineffective l HIV stays dormant for awhile (lysogeny) until some secondary infection strikes l helper T cells are quickly killed as HIV spreads, victim loses immunity Course of HIV-AIDS Review of specific immunity