Immunology Overview Quiz

Learning Objectives

• Students should be able to explain or identify terms in immunology.
• Students should be able to explain innate immunity, components, and reactions.
• Students should be able to explain adaptive immunity, components, and reactions.
• Students should be able to explain phagocytosis.
• Students should be able to explain molecular defenses.
• Students should be able to explain the characteristics of inflammation.
• Students should be able to explain the interferon and complement system.

Terminologies

• Immunity: The ability of an organism to recognize and defend against infectious agents.
• Susceptibility: The vulnerability of a host to harm by infectious agents, the opposite of immunity.
• Antigen: A toxin or substance that triggers an immune response, specifically the production of antibodies.
• Immune System: A network of cells and organs (e.g., thymus) that provide specific immunity against infectious agents.

Differences Between Antigen and Antibody

• Antigen: A substance, often a part of a foreign body like a bacterial cell, that elicits an immune response.
• Antibody: Molecules produced by the immune system to target and counteract antigens.

Types of Immunity

• Innate (genetic) immunity: Immunity determined by genetic traits, present in all humans, offering defense against various infectious agents.
• Adaptive (acquired) immunity: Immunity obtained through other means than heredity; can be naturally acquired (developing a disease) or artificially acquired (vaccine).

Toxoids

• Toxoids are normally toxic substances that have been processed to lose their toxicity.
• Toxoids retain their ability to trigger the immune system to produce antibodies.
• Toxoids are used in vaccines against diseases like diphtheria, tetanus, cholera.

How Antivenom is Made

• Snake venom is collected.
• Venom is injected into a horse to produce antibodies.
• Antibodies are extracted and purified.
• Purified antibodies are packaged and ready to use.

Innate and Adaptive Immunity

• Innate immunity: A broad defense system against various invaders.
• Adaptive immunity: A targeted immune response against specific agents like viruses or bacteria.

Adaptive Immunity

• Adaptive immunity involves the production of antibodies and the activation of lymphocytes.
• Lymphocytes are specific cells in the body's immune system, playing a key role in antibody and cellular responses.
• Adaptive immunity is usually more effective against succeeding infections than during the initial infection.

Innate Immunity

• Physical barriers: Skin and mucous membranes protect against external agents and secrete defensive molecules.
• Chemical barriers: Substances in body fluids (e.g., saliva) and acidity (e.g., in the stomach) inhibit microbial growth.
• Cellular defenses: Cells engulf and destroy invading organisms.
• Inflammation: Redness, swelling, and fever at infection sites are responses to tissue damage or infection.
• Fever: Elevated body temperature can kill invading agents and compromise their harmful effects.
• Molecular defenses: Interferon and complement destroy or impedes invading microorganisms.

Physical Barriers

• Skin and mucous membranes form physical barriers to prevent entry of infectious agents.
• Secretions and chemicals from these surfaces (e.g., saliva, tears) destroy pathogens.

Chemical Barriers

• High salt content in sweat and sebum from skin glands inhibit the growth of bacteria.
• Acidic pH in the stomach inhibits the growth of certain pathogens.
• Lysozyme in tears, saliva, and mucus destroys pathogens by disrupting their cell walls.

Cellular Defenses

• Basophils, mast cells, eosinophils, and neutrophils are granulocytes with specific roles such as initiating inflammatory responses or combating parasites.
• Neutrophils are phagocytic cells essential against infections that invade skin or mucous membranes.

Granulocytes

• Basophils release histamine, initiating inflammation.
• Mast cells trigger inflammation and allergies.
• Eosinophils are associated with allergic reactions and fighting parasites.
• Neutrophils are phagocytic cells that defend against infection.

Agranulocytes

• Monocytes turn into macrophages, crucial for engulfing microbes and debris.
• Lymphocytes, originating from lymphoid stem cells, contribute to adaptive immunity.
• Lymphocytes circulate in blood and are found in lymph nodes, spleen, thymus, and tonsils.

Phagocytes

• Phagocytes literally eat and engulf materials, like dead cells or pathogens, in body processes.
• Phagocytes (like macrophages and neutrophils) patrol body tissues.
• Phagocytosis: a process that involves phagocytes finding, adhering to, ingesting, and digesting microorganisms.

Inflammation

• The body has a chain reaction defense process when injured or infected.
• Inflammation is the body's response to tissue damage or infection, characterized by redness, heat, swelling, and pain (calor, rubor, tumor, dolor).
• Certain mediators, like histamine, cause inflammation.
• Pro-inflammatory mediators cause blood vessels to widen and increase blood flow

Molecular Defenses

• Interferons are small protein molecules that help cells resist viral infection(s).
• Other molecular defenses work as a cascade or a chain-reaction process.
• The complement system is a group of proteins aiding in killing pathogens and inflammatory responses.

Natural Killer Cells

• Natural killer (NK) cells are crucial for defending against infected or cancerous cells.

Complement System

• The complement system is a group of about 20 proteins that enhance the immune response.
• It enhances phagocytosis, directly kills pathogens, and initiates inflammatory responses.
• The complement system functions as a cascade or series of reactions to amplify some effect, such as cell killing or pathogen engulfment(s).

Opsonization

• Opsonins are molecules that enhance phagocytosis.
• Opsonins coat pathogens, making them more readily recognized and engulfed by phagocytic cells.

Immune Cytolysis

• Immune cytolysis refers to pathogen destruction by the immune system.
• This is facilitated through the formation of membrane attack complexes (MAC) which cause pathogen destruction by creating holes in the pathogen membrane.

Summary

• Innate and adaptive immunity are two primary defense mechanisms.
• Innate immunity is rapid and non-specific, while adaptive immunity is targeted and can develop immunity.
• Processes like phagocytosis, molecular defenses (e.g., interferons), and the complement system are crucial components of both systems.