Immunity and Defense Mechanisms Quiz

Immunity

• The body's ability to defend against infections caused by pathogens.
• It involves a complex system of defense mechanisms.

Pathogens

• Microorganisms that cause diseases.
• Examples: Bacteria, Viruses, Parasites.
• Must infect body cells to cause diseases.

Antigens

• Foreign particles that enter the body and stimulate the immune response.
• Recognized by the body's defense system as foreign substances.

Antibodies

• Proteins produced by lymphocytes to destroy antigens.
• Found on the surface of lymphocytes or released into the blood plasma.
• The interaction between antibodies and antigens is known as the immune response.

Lines of Defense

• Three main lines of defense against disease.
• First Line of Defense: Physical and chemical barriers that prevent pathogens from entering the body (e.g., skin, mucous membranes, lysozyme).
• Second Line of Defense: Non-specific mechanisms that fight pathogens that have entered the body (e.g., fever, phagocytosis, inflammation).
• Third Line of Defense: Specific immune response involving lymphocytes producing antibodies (e.g., B and T lymphocytes).

First Line of Defense

Lysozyme

• Antimicrobial protein that destroys bacteria.
• Found in tears, nasal mucus, and saliva.

Mucous Membrane

• Lines the respiratory tract.
• Secretes mucus that traps pathogens.

Blood Clotting

• Prevents bacteria from entering through wounds.

Hydrochloric Acid

• In the stomach, destroys bacteria in food and drinks.

Skin

• Physical barrier that prevents pathogen entry due to its thickness.
• Continuous shedding of dead skin cells makes it difficult for microorganisms to grow.
• Secretes sebum (oil and acid) that inhibits the growth of microorganisms.
• Sweat contains lysozyme.

Second Line of Defense

• Non-specific defense mechanisms.

Fever

• Increases phagocytic activity and fights against microorganisms.

Phagocytosis

• Process where phagocytes (neutrophils and monocytes) engulf and digest pathogens and dead cells.
• Phagocytes move to infected areas and enter tissue fluid through capillary pores.
• They contain lysozyme to digest pathogens.

Inflammation

• Immediate response to infection.
• Destroys and neutralizes harmful microorganisms and toxins.

Third Line of Defense

• Specific immune response involving lymphocytes.

Lymphocytes

• Produce antibodies and accumulate in lymph nodes during infection.
• Two types: T lymphocytes and B lymphocytes.
• T lymphocytes attack cells infected by pathogens.
• B lymphocytes produce antibodies that target specific antigens.

Lymph Nodes

• Contain lymphocytes and macrophages.
• Filter bacteria, dead tissues, and foreign particles.

Memory Cells

• Produced by B lymphocytes as a result of encounters with specific pathogens.
• Rapidly produce antibodies upon re-exposure to the same pathogen.

Antibody Actions

• Neutralization: Antibodies bind with toxins produced by bacteria, neutralizing them.
• Agglutination: Antibodies coagulate pathogens, making them easier for phagocytes to destroy.
• Precipitation: Antibodies react with dissolved antigens to form an insoluble complex (precipitate) that is easily destroyed by phagocytes.
• Lysis: Antibodies bind to antigens on bacteria causing cell destruction.

Immunity Types

• Active Immunity: Immune system produces its own antibodies in response to antigens.

  • Natural Active Immunity: Acquired after recovering from an infection.
  • Artificial Active Immunity: Acquired through vaccination.

• Passive Immunity: Body receives antibodies from an external source.

  • Natural Passive Immunity: Acquired from mother to fetus during pregnancy or through breastfeeding (transferred through placenta or breastmilk).
  • Artificial Passive Immunity: Acquired through injection of antiserum containing pre-made antibodies.

Vaccines

• Suspensions of weakened, dead, or non-virulent pathogens.
• Stimulate the immune system to produce antibodies without causing the disease.
• May require booster doses to maintain immunity.

HIV and AIDS

• HIV (Human Immunodeficiency Virus): Virus that attacks the human immune system.
• AIDS (Acquired Immunodeficiency Syndrome): Condition caused by HIV infection that weakens the immune system.

HIV Transmission

• Through body fluids like blood and semen.
• Can transfer from mother to child during pregnancy, birth, or breastfeeding.
• Also spread through contaminated needles and blood transfusions.

Symptoms of AIDS

• May not be visible for several years.
• Chronic diarrhea, fungal infections, and other opportunistic infections develop later.
• AIDS weakens the immune system, making individuals susceptible to other diseases.
• Ultimately, the immune system fails, and the individual dies from infections.

Differences between Artificial Active and Passive Immunity

Test your knowledge on the immune system and its various components, including pathogens, antigens, and antibodies. This quiz will explore the body's lines of defense against diseases and how it protects itself from infections.