Chapter 39 - The Body Defenses Immunity - refers to the body s ability to resist or eliminate potentially harmful foreign material s or abnormal cells Mechanisms include: 1. Defense against invading pathogens (disease-producing microorganisms such as viruses & bacteria) - major targets of the immune system 2. Removal of worn-out cells & tissue debris 3. Identification & destruction of abnormal or mutant cells 4. Allergies & autoimmune responses 5. Rejection of tissue cells of foreign origin
Immune system cells Chapter 39 - The Body Defenses 1. Neutrophils - mobile, phagocytic specialists 2. Eosinophils - secrete chemicals toxic to pathogens 3. Basophils - secrete histamine & heparin 4. Monocytes -phagocytes 5. Lymphocytes A) B lymphocytes (B-cells) which are transformed into plasma cells, which secrete antibodies that indirectly lead to the destruction of the foreign material B) T lymphocytes (T-cells) which are transformed into cytotoxic T-cells, which directly destroy virus-invaded cells & mutant cells via nonphagocytotic means
Chapter 39 - The Body Defenses Immune responses are either nonspecific or specific Nonspecific immune response 1. Inflammation - neutrophils & monocytes play a major role 2. Interferon - a family of proteins that nonspecifically defend against viral infection 3. Natural killer cells - a special class of lymphocyte-like cells that spontaneously lyse (destroy) virus-infected host cells & cancer cells 4. The complement system - a group of inactive plasma proteins that when activated attack & destroy the plasma membranes of foreign cells Inflammation Goal of the inflammatory response is to bring to the invaded or injured area phagocytes & plasma proteins that: 1. Isolate, destroy, or inactivate the invader 2. Remove debris 3. Prepare for subsequent healing & repair 4. Phagocytes secrete endogenous pyrogen which induces a fever
Chapter 39- Blood
Chapter 39- Blood
Interferon Released from virus-infected cells Chapter 39 - The Body Defenses Inhibits multiplication of viruses in most cells Mechanism Virus enters first cell, & this cell releases interferon as a response Interferon binds with receptors on uninfected cells, & initiates the production of inactive enzymes capable of breaking down viral RNA Once the virus enters this primed cell, the enzymes are activated & the viral RNA is destroyed - virus is DEAD!
Natural killer cells Chapter 39 - The Body Defenses Naturally occurring, lymphocyte like cells that lyse virus-infected cells Complement system Circulating plasma proteins (9) in an inactivated form When activated, complement proteins 5-9 will combine & insert themselves into the cell membrane of a target cell, lysing it
Chapter 39- Blood
Specific Immune Response Divided into: 1. Humoral (antibody-mediated) immunity 2. Cell mediated immunity Chapter 39 - The Body Defenses How is the specific immune response stimulated? Antigens are molecules that stimulate the immune response to attack it Antigenic determinant sites are found on complex antigens & may stimulate the immune system to attack it with multiple antibodies
Chapter 39 - The Body Defenses Humoral immunity Antibodies are the attackers for this immune response Secreted by plasma cells which are produced via B-cell differentiation
Chapter 39- Blood
Antibody structure Chapter 39 - The Body Defenses Composed of 2 heavy chains & 2 light chains linked together = arranged in a Y Tips of the Y = antigen binding fragments (Fab) Tail portion = constant region (Fc) - interacts with immune cells Antibody actions 1. Neutralization - antibodies bind with bacterial toxins or viruses, preventing them from interacting with cells 2. Agglutination clumping & precipitation insoluble - prevent proper functioning - minor action - more important in diagnostics 3. Activation of complement system - activation of complement system proteins which attack the cell membrane of the invading cell 4. Enhancement of phagocytosis - antibody tails bind with phagocytes 5. Stimulation of Killer cells (non-specific) - recognize antibody tails
Cell mediated immunity 1. T-cells 2. Attack infected self cells 3. Differentiation into several cell types: Cytotoxic T-cells A) Cytotoxic T-cells B) Helper T-cells C) Suppressor T-cells D) Memory T-cells Chapter 39 - The Body Defenses 1. Destroy infected self cells via secretion of perforin 2. Perforin (perforating) creates holes in the target cell s membrane 3. Indirectly destroy target cells by inducing apoptosis via the secretion of chemicals 4. The cytotoxic T-cells can only destroy self cells, only if those cells present the foreign antigen on class I MHC (major histocompatibility) proteins (self proteins)
Chapter 39 - The Body Defenses Helper T-cells 1. Secretion of B-cell growth factor 2. Secretion of T-cell growth factor (Interleukin 2) 3. 60-80% of all circulating T-cells 4. Commander cell
Suppressor T-cells 1. Inhibit the immune response Chapter 39 - The Body Defenses 2. Activated by T-helpers but slow to develop Memory T-cells 1. Provide rapid mobilization of the immune response if the system is subsequently exposed to the same antigen
Chapter 39 - The Body Defenses How is the specific immune response initiated? 1. Foreign antigen must be phagocytized by a macrophage which will present the antigen properly to the lymphocytes (T & B) 2. The macrophage will present the antigen on specific class II MHC receptor proteins, which are found on the surfaces of special immune cells (B-cells, cytotoxic T-cells, & macrophages) 3. Binding of the lymphocytes to the presented antigen will activate them 4. B-cells & T-helper cells will recognize the antigen-mhc complex on the macrophage 5. Activated T-helpers secrete a B-cell growth factor which will stimulate B-cell differentiation into plasma cells (humoral immunity) 6. Interleukin 1 secreted by the macrophage will also stimulate B-cell differentiation 7. Some B-cells will differentiate into memory B-cells for long term immunity = important for fast, secondary response (i.e. won t get sick again) 8. Activated T-helpers secrete T-cell growth factor which activates cytotoxic T-cells (cell-mediated immunity)
Chapter 39- Blood
Chapter 39- Blood
Chapter 39- Blood
Chapter 39- Blood
Chapter 39 - The Body Defenses Specific Immunity & Hemolytic disease of the newborn Rh factor is a surface antigen on RBCs If mom is Rh negative & gives birth to Rh postive baby = mom will have an immune response against the Rh antigen = develop antibodies against the Rh antigen & will attack any subsequent Rh positive baby
Chapter 39- Blood