Chapter 11: Human Immunity Flashcards

Practice flashcards reviewing Chapter 11: Human Immunity concepts including lines of defence, antibody actions, types of immunity, and related health issues.

What is the biological definition of immunity?

Immunity is the body's ability to resist disease infections caused by pathogens or foreign substances through a specific attack against those pathogens.

What is an antigen?

An antigen is a foreign substance that enters the body and stimulates an immune response.

What are antibodies?

Antibodies are proteins found on the surface of lymphocytes or released by lymphocytes into the blood plasma to interact with and destroy specific antigens.

What constitutes the body's first line of defence?

Physical barriers (such as skin) and chemical barriers (such as sebum, sweat, lysozyme enzyme, mucous membranes, hydrochloric acid, and the blood clotting mechanism) that prevent pathogens from entering the body.

How does hydrochloric acid in the stomach act as a defence mechanism?

Hydrochloric acid destroys bacteria present in ingested food and drinks.

What is lysozyme, and where is it found in the human body?

Lysozyme is an antimicrobial protein enzyme that breaks down bacterial cell walls; it is present in tears, nasal discharge, saliva, sweat, and mucus.

Which three non-specific mechanisms make up the body's second line of defence?

Fever, phagocytosis, and inflammation.

Which types of white blood cells carry out phagocytosis?

Neutrophils and monocytes.

What are the sequential steps of phagocytosis illustrated in this diagram?

1. The phagocyte extends a pseudopodium toward bacteria and engulfs them.
2. Ingestion forms a phagosome.
3. The phagosome combines with a lysosome, which secretes lysozyme into the phagosome.
4. Bacteria inside the phagosome are destroyed by lysozyme.
5. The phagocyte expels digested waste outside the cell.

What substance is released by damaged tissues to initiate an inflammatory response?

Histamine.

What role does histamine play during an inflammation response?

Histamine dilates blood capillaries to increase blood flow to the infection site and increases capillary permeability to allow phagocytes to reach the infected area.

What is pus composed of?

Pus is a mixture of microorganisms, tissue debris, and white blood cells found at sites of infection or damaged tissue.

What are the distinct functions of T lymphocytes and B lymphocytes in the third line of defence?

T lymphocytes attack cells infected by pathogens and stimulate B lymphocytes to produce memory cells; B lymphocytes produce antibodies and memory cells.

How do antibodies destroy bacterial toxins through neutralisation?

Antibodies bind directly to toxins secreted by bacteria and neutralise their harmful effects.

What occurs during antibody-mediated agglutination?

Antibodies clump pathogens together, making them easier for phagocytes to trap and engulf.

How does opsonisation assist phagocytes in destroying pathogens?

Antibodies bind to antigens and serve as markers, allowing phagocytes to recognise and engulf the pathogens.

What occurs during antibody-mediated lysis (penguraian)?

Lysin antibodies bind to antigens on the bacterial wall, causing the bacteria to burst and break down.

What is precipitation in the context of antibody action?

Antibodies react with soluble antigens to form an insoluble complex (precipitate) that is easily ingested and destroyed by phagocytes.

How is natural active immunity acquired, and how long does it last?

It is acquired after recovering from a disease (such as chickenpox or influenza) and provides long-lasting or permanent immunity.

What is artificial active immunity, and how is it induced?

It is acquired through a vaccine injection (containing weakened, dead, or non-virulent pathogens) that stimulates lymphocytes to produce their own antibodies.

Why is a booster dose required following a primary vaccine injection?

The primary injection produces a low antibody level below the level of immunity; a booster dose elevates antibody production above the level of immunity to ensure protection.

How does a fetus or newborn baby obtain natural passive immunity?

A fetus acquires maternal antibodies that cross the placenta into its bloodstream, and a newborn receives antibodies through breast milk or colostrum during breastfeeding.

What is artificial passive immunity, and when is it administered?

It is acquired through an injection of antiserum containing specific pre-formed antibodies (e.g., antitetanus, anti-rabies, or snake antivenom) to provide immediate, short-term protection.

What does 'level of immunity' (aras keimunan) mean?

It refers to the concentration of antibodies in the blood that is sufficient to successfully fight off a specific infection.

What is AIDS, and what pathogen causes it?

AIDS stands for Acquired Immuno Deficiency Syndrome, and it is caused by the Human Immunodeficiency Virus (HIV).

How does HIV impair the human immune system?

HIV infects and replicates inside lymphocytes, progressively destroying them until the immune system becomes severely compromised and unable to defend against opportunistic infections.

What are the primary modes of HIV transmission?

Transfer of bodily fluids such as blood and semen (through unprotected sex, sharing contaminated needles, or blood transfusions) and transmission across the placenta, during birth, or via breastfeeding from an infected mother.