Immune System Notes.docx

18 Pages

Biological Sciences Program
Course Code
BSCI 201
Justicia Opoku

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Immune System Body Defenses: The Immune System The body is constantly in contact with protists, bacteria, fungi, and viruses The body has two defense systems for foreign materials Innate defense system (nonspecific defense system) Mechanisms protect against a variety of invaders Responds immediately to protect body from foreign materials Adaptive defense system (specific defense system) is a specific defense is required for each type of invader We can develop immunity or specific resistance to certain pathogens Innate (Nonspecific) body defenses: First line defense Physical Barriers Skin is a physical barrier to foreign materials mucous membranes mucus traps microorganisms in digestive and respiratory pathways. Chemical Barriers Secretions from sebaceous and sweat glands (salty sweat), sebum is toxic to bacteria Sebaceous glands secrete oily substances into hair follicles Urine Vaginal secretions are acidic pH of the skin is acidic to inhibit bacterial growth Stomach Mucosa and secrete hydrochloric acid, also has protein-digesting enzymes Hydrochloric acid can also kill a lot of pathogens that exist or might exist on the food Certain pathogens are dormant until they stay in contact with hydrochloric acid. Red Queen Hypothesis: Both pathogens and hosts are constantly evolving so they have the best chance of the survival Immune system is the driving force behind evolution Lysozymes in tears, sweat, saliva, etc can break down bacteria. Nonspecific immune System’s general Response: Flu-like Symptoms Body’s generic response Fever Makes the body’s environment uncomfortable or inhospitable Runny nose and watery eyes Mucus flushes out pathogens Fluid and mucus in lungs Flushes out pathogens Diarrhea Flushes out pathogens Rash More of an alert system Achy muscles More of an alert system Fatigue Innate (nonspecific) body defenses: Second line of defense Fever Abnormally high body temperature Hypothalamus heat regulation can be reset by pyrogens (secreted by white blood cells) Apyrogen is substance than can cause fever High temperatures inhibit the release of iron and zinc from the liver and spleen needed by bacteria Fever also increases the speed of tissue repair. Heat increases the density of sticky molecules on the surface of blood vessels in the lymph nodes, which catch more white blood cells as the blood rushes past. Innate (nonspecific body Defense: Second Line of Defense: Phagocytosis Phagocytosis is a process Neutrophils move by diapedesis (movement of blood cells through capillary walls) to clean up damaged tissue and/or pathogens Monocytes become macrophages and complete disposal of cell debris Phagoctyes are a cell type Cells such as neutrophils and macrophages engulf foreign material into a vacuole. Enzymes from lysosomes digest the material. Innate (Nonspecific) Body Defenses: Second Line of Defense: Natural Killer Cells Natural Killers (NK) cells Can lyse (disintegrate or dissolve) and kill cancer cells Can destroy virus-infected cells Innate (Nonspecific) Body Defenses: Second line of defense: Inflammation Functions of the inflammatory response Prevents the spread of damaging agents Disposes of cell debris and pathogens through phagocytosis. Sets the stage for repair Inflammatory response Triggered when body tissues are injured Series of events causing accumulation of proteins, fluids, and phagocytosis Four most common indications of acute inflammation Redness Heat Swelling Pain Results in a chain of events leading to protection and healing. Pain Pain modifies and alters behaviors Pain responses are temporarily delayed. Reflex to move away from pain is faster than the understanding that there is pain Innate (Nonspecific) Body defenses: Second line of Defense: antimicrobial proteins Antimicrobial proteins Attack microorganisms Hinder reproduction of microorganisms Most important antimicrobial proteins Complement proteins Uses a MAC (membrane attack complex) proteins to lyse cells May be part of the specific (adaptive) or nonspecific (innate) immune response. Interferon Proteins secreted by virus-infected cells Bind to healthy cell surfaces to interfere with the ability of viruses to multiply. Stops protein synthesis. Second Line of defense: Complement system: plasma proteins that lyse foreign cells, especially bacteria. Response involves ~ 30 proteins in cascade resulting in MAC on surface of bacteria MAC pierces bacterial membrane causing lysis Triggers histamine release from mast cell May act as opsonins (working with antibodies) Alternate Pathway Binding to carbohydrates on bacterial cell walls Part of nonspecific defense mechanisms. Classical Pathway Binding to antibodies attached to bacteria Part of specific defense mechanisms Specific (Adaptive) Immune responses: Third line of Defense Specific immune responses trigged by foreign matter reaching lymphoid tissue Antibodies are proteins that protect from pathogens Aspects of Adaptive defense Antigen specific, recognizes and acts against particular foreign substances Systemic, not restricted to the initial infection site Memory, recognizes and mounts to a stronger attack on previously encountered pathogens Can recognize self from non-self Specific (Adaptive) Immune Responses: Third Line of Defense Types of Immunity Humoral immunity is antibody – mediated immunity is B cell mediated Humors – refers to the fluid in the body Provided by antibodies present in body fluids Involves secretion of antibodies by plasma cells Defense against bacteria. toxins, viruses in body fluids Cellular immunity – T cell-mediated immunity Targets Virus-infected cells, cancer cells, and cells of foreign grafts Involves lysis of cells by cytotoxic T cells Defend against bacteria, viruses in body cells Part of reaction to transplant and cancer cell Antigen Presenting Macrophages present to the Helper T cells the nametag of the Bacterial Cells Specific (Adaptive) Immune Responses Third Line of Defense Antigens (nonself are very specific) Any Substance capable of exciting the immune system and provoking an immune response Antigens Complex proteins/polysaccharides Part of foreign invader, tumor cell Epitopes – recognition sites on pathogen/antigen for B or T cells. B cell and T cell specificity Antigens recognize certain antigens only B cells – membrane antibodies T cells – T cell receptors Self-Antigens Human cells have many surface proteins Our immune cells do not attack our own proteins Our cells in another person’s body can trigger an immune response because they are foreign and restricts donors for transplants. Specific (Adaptive) Immune Responses: Third line of defense Immunocompetent – cell becomes capable of responding to a specific antigen by binding to it Cells of theAdaptive Defense system Lymphocytes Originate from hemocytoblasts in the red bone marrow B lymphocytes become immunecompetent in the bone marrow (remember B for Bone Marrow) T lymphocytes become immunocompetent in the thymus (remember T for Thymus) Macrophages Arises from monocytes Become widely distributed in lymphoid organs Secrete cytokines (proteins important in the immune response) Self-Tolerance B and T cells do not attack normal cells od body As cells develop in bone marrow and thymus, any that have antigen receptors against normal body cells are destroyed by apoptosis (programmed cell death) Autoimmune diseases caused by failure of self-tolerance MHC molecules unique to individual person Major histocompatibility complex – MHC MHC marks body cells as self Responsible for tissue/organ rejection – stimulates immune response to foreign tissue. Specific (adaptive) Immune Responses: Third line of Defense: T cells and Cellular Immunity T cells defense against foreign or abnormal matter through direct contact T Cell Clones Cytotoxic (killer) T cells Specialize in killing infected cells Insert a toxic chemicals (perforin/Fragmentin) Helper T cells Recruit other cells fight to the invaders Interacts directly with B cells Regulatory (suppressor T cells) Release ch
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