kasmo-ogaal

Chapter 4: Immunology (Immune System)

22. What is immunity?

Immunity is the ability of an organism to protect itself against a particular infection or toxin.

23. What is immunology?

Immunology is the study of the physiological defense mechanisms by which the body destroys or neutralizes toxins released by bacteria.

24. What is the function of immune defense?

• Protects the body against foreign substances.
• Defense mechanisms are not unique to one specific foreign substance.

25. What are the two types of immune system?

• Specific immune system (acquired immunity)
• Non-specific immune system (innate immunity)

26. What does specific immune system perform?

It depends on specific recognition of substances by lymphocytes.

27. What does non-specific immune system perform?

• Protects against microbes such as viruses, bacteria, and parasites
• Removes anti-microbial substances
• Destroys cancer cells

28. How does the immune system recognize pathogens?

• Plasma membrane receptors
• Circulatory proteins (complement system) that bind to microbial cell walls

29. What are the categories of non-specific immunity?

First line of defense:

• Skin – acidic pH (3–5) inhibits microorganisms
• Digestive tract – saliva and stomach acid kill microbes
• Respiratory tract – mucus and cilia trap and remove microbes
• Blood clotting

Second line of defense:

• White blood cells (WBC)
• Phagocytes (macrophages and neutrophils)
• Lymphocytes

30. Define the following terms:

• Phagocytes: Scavenger cells produced in bone marrow that engulf pathogens.
• Macrophages: Phagocytes found in organs such as lungs, liver, spleen, and lymph nodes.
• Neutrophils: Short-lived phagocytes that protect tissues during infection.

31. What is the difference between T-cells and B-cells?

• B-cells mature in the bone marrow and are short-lived.
• T-cells mature in the thymus gland and are long-lived.

32. Define thymus gland.

The thymus is a gland located beneath the sternum where T-cells mature.

33. What are the types of cells formed from lymphocytes?

• Plasma cells
• Memory cells

34. Which lymphocytes carry out immune responses?

Only mature lymphocytes can carry out immune responses.

35. What is a clone?

A clone is a group of identical cells formed from a single parent cell.

36. Define antigen.

An antigen is a substance capable of stimulating an immune response.

37. Define antibodies.

Antibodies are proteins produced in response to antigens.

38. Describe the structure of antibodies.

Antibodies consist of two identical light chains and two identical heavy chains joined by disulfide bonds to form a Y-shaped molecule.

39. Where do antibodies bind antigens?

Antigens bind to the arms of the Y-shaped antibody, which have variable amino acid sequences.

40. What is the function of the hinge region?

It provides flexibility, allowing antibodies to bind to antigens effectively.

41. What are the functions of antibodies?

• Identify antigens
• Prevent bacteria from attaching to tissues
• Neutralize viruses

42. What are the types of T-cells and their functions?

• T-helper cells: Release cytokines to stimulate B-cells.
• T-killer cells: Destroy infected cells.
• Suppressor T-cells: Stop immune response after recovery.

43. Define active immunity.

Active immunity develops when antigens enter the body and stimulate antibody production.

44. Types of active immunity.

• Natural active immunity
• Artificial active immunity

45. Define passive immunity.

Passive immunity is immunity gained from antibodies supplied from outside the body.

46. Types of passive immunity.

• Inherited immunity
• Vaccination

47. How does antigenic concealment occur?

• Some pathogens live inside body cells (e.g. Plasmodium)
• Some disguise themselves using host proteins
• Some infect T-helper cells (e.g. HIV)

© 2026 | Biology – Chapter 4 Immunology