Immune System Structures & Terms PDF

Immune System – Structures/Terms. Pathogens (Infectious Agents). Bacteria: Single-celled microorganisms that can cause a variety of infections. Viruses: Tiny infectious agents that can only reproduce inside the cells of other organisms. Fungi: Organisms that include yea...

Immune System – Structures/Terms. Pathogens (Infectious Agents). Bacteria: Single-celled microorganisms that can cause a variety of infections. Viruses: Tiny infectious agents that can only reproduce inside the cells of other organisms. Fungi: Organisms that include yeasts, molds, and mushrooms, some of which can cause infections. Protozoans: Single-celled organisms, some of which can cause diseases like malaria. Parasitic Worms: Multicellular organisms that can live inside the human body and cause infections. White Blood Cells (Leukocytes). Granulocytes o Neutrophils: The most common type of white blood cell, crucial for fighting bacterial infections. o Eosinophils: Involved in allergic reactions and combating parasitic infections. o Basophils: Release histamine and other chemicals involved in inflammation. o Mast Cells: Similar to basophils, found in tissues and contribute to allergic reactions. Agranulocytes. o Lymphocytes ▪ T cells: Play a central role in cell-mediated immunity, attacking infected cells and regulating the immune response. ▪ B cells: Responsible for producing antibodies, which target specific pathogens. ▪ NK cells: Natural killer cells, which can destroy infected or cancerous cells without prior activation. o Monocytes ▪ Macrophages: Large phagocytic cells that engulf and destroy pathogens and cellular debris. ▪ Dendritic Cells: Capture and present antigens to T cells, initiating an immune response. Cytokines Interleukin (IL): A group of signaling molecules that regulate immune cell function and communication. Tumor Necrosis Factor: A cytokine that promotes inflammation and can induce cell death. Colony-Stimulating Factor (CSF): Stimulates the production of white blood cells in the bone marrow. Interferon (IFN): A group of cytokines that interfere with viral replication and activate immune cells. White Blood Cell Tests. White Blood Cell Count: Measures the total number of white blood cells in the blood. White Blood Cell Differential: Determines the percentage of each type of white blood cell. White Blood Cell Disorders. Leukopenia: Abnormally low white blood cell count, increasing the risk of infections. Leukocytosis: Abnormally high white blood cell count, often indicating an infection or inflammation. Leukemia: Cancer of the blood-forming cells, leading to an overproduction of abnormal white blood cells. o Chronic Myeloid (Myelogenous) Leukemia: Affects myeloid cells, progresses slowly. o Acute Myeloid (Myelogenous) Leukemia: Affects myeloid cells, progresses rapidly. o Chronic Lymphoid (Lymphocytic) Leukemia: Affects lymphoid cells, progresses slowly. o Acute Lymphoid (Lymphocytic) Leukemia: Affects lymphoid cells, progresses rapidly. Innate (Nonspecific) Immunity, First Line of Defense: Prevent Entry of Pathogens This refers to the inherent, non-specific defenses that the body employs to prevent pathogens from entering in the first place. Skin Epidermis: The outermost layer of skin, acting as a physical barrier. It's constantly shedding (exfoliation), helping remove microbes. Dermis: The layer beneath the epidermis, containing blood vessels, sweat glands, and hair follicles. It provides structural support and nourishes the epidermis. Normal Flora: Beneficial bacteria and other microorganisms that reside on the skin, competing with harmful microbes for space and resources. Exfoliation: The shedding of dead skin cells, which also helps remove microbes from the skin surface. Hyaluronic Acid: A substance in the skin that helps retain moisture, creating an environment less favorable for some microbes. Sebum (Oil): Secreted by sebaceous glands, it lubricates the skin and has a slightly acidic pH, which can inhibit the growth of some microbes. Sweat: Contains salts and other substances that can create an environment less hospitable to some microbes. Mucous Membranes. Epithelial Tissue: The thin layer of cells lining the mucous membranes, acting as a barrier. Connective Tissue: Provides support and structure to the mucous membranes. Normal Flora: Like on the skin, beneficial microbes reside in mucous membranes, competing with harmful ones. Mucus: A sticky substance secreted by goblet cells that traps microbes and other particles. Respiratory Tract. Nasal Mucus: Traps microbes and other particles inhaled through the nose. Vibrissae (Guard Hairs): Hairs in the nose that filter out larger particles from inhaled air. Cilia: Tiny hair-like structures lining the respiratory tract that move mucus and trapped particles upward, away from the lungs. Coughing & Sneezing: Reflexes that help expel mucus and trapped particles from the respiratory tract. Gastrointestinal Tract. Saliva: Contains enzymes (like lysozyme) that can break down some microbes. Hydrochloric Acid (HCl): The strong acid in the stomach creates a highly acidic environment that kills many microbes. Defecation & Vomiting: Help expel harmful substances or microbes from the body. Urinary and Reproductive Tracts. Urine: The flushing action of urine helps remove microbes from the urinary tract. Lactic Acid (Lactate): Produced by normal flora in the vagina, creating an acidic environment that inhibits the growth of some microbes. Secretions Produced by Skin and Mucous Membranes. Lysozyme: An enzyme that breaks down bacterial cell walls. Defensins & Dermicidin: Antimicrobial peptides that can kill a variety of microbes. Immunoglobin A (IgA): An antibody found in secretions like mucus, tears, and saliva that helps neutralize microbes. Other Secretions. Lacrimal Fluid (Tears): Contains lysozyme and other substances that help protect the eyes from infection. Cerumen (Ear Wax): Protects the ear canal by trapping microbes and other particles. Key Takeaway. The innate immune system provides a crucial first line of defense through a combination of physical barriers, chemical defenses, and mechanical actions. These work together to prevent the entry and establishment of pathogens in the body Innate (Nonspecific) Immunity, Second Line of Defense: Nonspecific Internal Defenses. This line of defense involves a variety of internal mechanisms and cells that work together to identify and eliminate pathogens that have breached the first line of defense. White Blood Cells.  Neutrophils: Phagocytes that are the first responders to infection sites. They engulf and destroy bacteria, fungi, and other pathogens. Macrophages: Large phagocytes derived from monocytes that can migrate into tissues and engulf pathogens, cellular debris, and foreign particles. They also act as antigen-presenting cells, activating the adaptive immune system. Dendritic Cells: Antigen-presenting cells found in tissues throughout the body. They capture and present antigens to T cells, initiating an immune response. Basophils: Release histamine and other inflammatory mediators, contributing to allergic responses and inflammation. Mast Cells: Similar to basophils, found in tissues and involved in allergic reactions and inflammation. Natural Killer (NK) Cells: Lymphocytes that can directly kill infected or abnormal cells without prior activation. They play a role in viral defense and tumor surveillance. Eosinophils: Involved in allergic reactions and parasitic infections. They release enzymes and other substances that can damage parasites and kill cells. Antimicrobial Proteins. Cytokines: Signaling molecules produced by immune cells that regulate various aspects of the immune response. Examples include interferons, interleukins, and tumor necrosis factor. Interferon (IFN): Proteins produced by infected cells that signal neighboring cells to enter an antiviral state, inhibiting viral replication. Complement System: A group of plasma proteins that work together to lyse pathogens, promote inflammation, and enhance phagocytosis. Inflammation. A localized response to tissue injury or infection, characterized by redness, heat, swelling, pain, and loss of function. It involves the release of inflammatory chemicals like histamine, kinins, and leukotrienes, which cause vasodilation, increased capillary permeability, and white blood cell migration to the site of injury. Inflammatory Chemicals. Histamine: A molecule released by mast cells and basophils that causes vasodilation, increased capillary permeability, and smooth muscle contraction.  Kinins: Peptides involved in pain, inflammation, and blood pressure regulation. Leukotrienes: Lipid mediators that contribute to inflammation, particularly in the airways. Blood Flow. Vasodilation: The widening of blood vessels, increasing blood flow to the injured area to deliver oxygen, nutrients, and white blood cells. Capillary Permeability: The increased permeability of blood vessel walls, allowing white blood cells and plasma proteins to leak out into the tissues. White Blood Cells. Margination: The process by which white blood cells adhere to the walls of blood vessels at the site of injury. Diapedesis: The movement of white blood cells through the walls of blood vessels into the tissues. Chemotaxis: The movement of white blood cells toward the site of injury or infection in response to chemical signals. Phagocytosis. The process of engulfing and destroying pathogens, cellular debris, and foreign particles by phagocytes. Plasma Proteins. Complement Proteins: Components of the complement system that work together to lyse pathogens, promote inflammation, and enhance phagocytosis. Antibodies: Proteins produced by B cells that bind to specific antigens on pathogens, activating the immune system to destroy them. Cardinal Signs of Inflammation. Redness (rubor, erythemia): Caused by increased blood flow and vasodilation. Heat (calor): Caused by increased blood flow and metabolic activity at the site of injury. Swelling (tumor, edema): Caused by the accumulation of fluid in the tissues due to increased capillary permeability.  Pain (dolor): Caused by the release of inflammatory chemicals and the stimulation of nerve endings. Loss of Function: Can occur if the inflammation is severe or affects a joint or muscle. Fever. An elevated body temperature in response to infection or inflammation. It is triggered by the release of pyrogens, which act on the hypothalamus to increase body temperature. Chemicals of Fever. Pyrogens: Substances released by immune cells and other cells that trigger fever. Prostaglandins: Lipid mediators that promote inflammation and fever. Stages of Fever. Onset: The initial rise in temperature. Stadium: The period of sustained elevated temperature. Defervescence: The gradual return of body temperature to normal. Key Points. The second line of defense involves a variety of internal mechanisms and cells that work together to identify and eliminate pathogens that have breached the first line of defense. Inflammation is a key component of this response, involving the release of inflammatory chemicals and the recruitment of white blood cells to the site of injury. Adaptive (Acquired/Specific) Immunity, Third Line of Defense: Pathogen-Specific Immunity. This sophisticated immune system branch is characterized by its ability to recognize specific pathogens and tailor its response accordingly. It's slower to react than the innate immune system but offers long-lasting protection through memory. Key Terms.  Antigens: Molecules that trigger an immune response. They can be foreign (like pathogens) or self (produced by the body's own cells). Self: Molecules or antigens produced by the body's own cells. The immune system normally tolerates self-antigens. Foreign: Molecules or antigens that are not produced by the body's own cells. The immune system recognizes these as foreign and mounts a response to destroy them. Tumor: A mass of abnormal cells that can grow uncontrollably. Some tumors express antigens that are recognized as foreign by the immune system. Lymphocytes: White blood cells that are central to the adaptive immune system. They include T cells and B cells. Formation: Lymphocytes are formed in the bone marrow, where they mature into different types. Red Bone Marrow: The primary site of blood cell production, including lymphocytes. Thymus: A gland located in the chest where T cells mature and undergo selection. Activation: The process by which lymphocytes are activated to recognize and respond to antigens. Secondary Lymphatic Structures: Organs and tissues, such as lymph nodes, spleen, and tonsils, where lymphocytes encounter antigens and are activated. Effector Response: The actions taken by activated lymphocytes to eliminate pathogens or neutralize antigens. T cells: A type of lymphocyte that plays a central role in cell-mediated immunity. They are divided into several types, including T helper cells, T cytotoxic cells, and T regulatory cells. o T Helper Cells (T H ): Activate other immune cells, including B cells and macrophages. o T Cytotoxic Cells (T C ): Directly kill infected or abnormal cells. o T Regulatory Cells (T R ): Suppress the immune response to prevent autoimmune reactions. o T Memory Cells (T M ): Remember past encounters with antigens and allow for a rapid response upon re-exposure. B cells: A type of lymphocyte that produces antibodies. They are activated by T helper cells and differentiate into plasma cells and memory cells. o B Plasma Cells (B P ): Produce antibodies that bind to specific antigens and neutralize them.  o B Memory Cells (B M ): Remember past encounters with antigens and allow for a rapid response upon re-exposure. Antibody Structure: A Y-shaped molecule consisting of two heavy chains and two light chains. The variable region of the antibody binds to a specific antigen, while the constant region determines the antibody's function. Antigen Binding Site: The region at the tip of the variable region of an antibody that recognizes and binds to a specific antigen. Antibody Function: Antibodies have various functions, including: o Neutralization: Blocking the ability of a pathogen to infect cells. o Agglutination: Clumping pathogens together, making them easier to phagocytose. o Precipitation: Forming insoluble complexes with antigens, which can be removed from the body. o Complement Fixation: Activating the complement system to lyse pathogens and promote inflammation. o Opsonization: Coating pathogens with antibodies to enhance their phagocytosis. o NK Cell Activation: Activating natural killer cells to destroy infected or abnormal cells. Antibody Production: The process by which B cells produce antibodies in response to antigen stimulation. Primary Response: The initial immune response to a new antigen, which takes several days to develop. Secondary Response: The faster and stronger immune response to a previously encountered antigen, due to the presence of memory cells. Key Points. The adaptive immune system is highly specific and adaptable, allowing the body to mount a tailored response to a wide range of pathogens. It relies on the recognition of antigens by lymphocytes, which are activated to produce antibodies and destroy infected or abnormal cells. The memory component of the adaptive immune system allows for rapid and effective responses to repeated exposures to the same antigen Three Rs of Immunity. Recognize: The immune system's ability to detect and identify foreign substances (antigens) or abnormal cells.  React: The immune system's ability to respond to recognized threats by launching an attack to eliminate them. Remember: The immune system's ability to retain a memory of previous encounters with antigens, enabling a faster and stronger response upon subsequent exposures. Active and Passive Immunity. Active Immunity: Immunity acquired when the body produces its antibodies in response to exposure to an antigen. o Naturally Acquired: Occurs through exposure to a pathogen, leading to infection and subsequent immune response. o Artificially Acquired: Occurs through vaccination, where a weakened or inactive form of a pathogen is introduced to stimulate an immune response without causing illness. Passive Immunity: Immunity acquired by receiving pre-formed antibodies from another source. o Naturally Acquired: Occurs when antibodies are passed from mother to fetus across the placenta or through breast milk. o Artificially Acquired: Occurs through the injection of antibodies, such as immune globulin, to provide immediate protection against a specific disease. Immune System Disorders. Allergies (Hypersensitivities): Exaggerated immune responses to harmless substances (allergens). o Allergic Rhinitis (Hay Fever): An allergic reaction to airborne allergens, causing sneezing, runny nose, and itchy eyes. o Hives: An allergic skin reaction characterized by itchy welts. o Asthma: A chronic respiratory condition characterized by inflammation and narrowing of the airways, often triggered by allergens. o Anaphylaxis: A severe, life-threatening allergic reaction that can cause difficulty breathing, swelling, and shock. Severe Combined Immunodeficiency Disease (SCID): A group of rare genetic disorders that severely impair the immune system, leaving individuals highly susceptible to infections.  Acquired Immunodeficiency Syndrome (AIDS): A condition caused by the human immunodeficiency virus (HIV), which attacks and weakens the immune system, making individuals vulnerable to opportunistic infections and cancers. Key Points. The three Rs (Recognize, React, Remember) are the fundamental principles underlying the immune system's function. Active immunity involves the body's own production of antibodies, while passive immunity involves receiving pre-formed antibodies from another source. Immune system disorders can result from an overactive immune response (allergies) or a weakened immune system (SCID, AIDS).