Class 10 Biology – Chapter 9: Immunity and the Immune System

Board: Federal Board (FBISE)

Section I: Multiple Choice Questions

Select the correct answer.

Q1. Cytotoxic cells are:

A) The same as memory T cells
B) Cells that suppress the immune response
C) T cells that are actively killing other cells
D) Inactive T cells carried in the plasma

Correct Answer: C) T cells that are actively killing other cells

Q2. Antibodies provide adaptive immunity by:

A) Attaching to specific antigens
B) Killing pathogens after recognition
C) Neutralizing toxins by combining with them
D) All of the above

Correct Answer: D) All of the above

Q3. The innate immune system can protect us from disease by acting on:

A) Specific pathogens only
B) All types of invaders
C) Producing antibodies
D) Recognizing pathogens

Correct Answer: B) All types of invaders

Q4. Fever is harmful for:

A) Our normal metabolism
B) Growth of pathogens
C) Our growth and development
D) Working of the immune system

Correct Answer: A) Our normal metabolism

Q5. Macrophages and dendritic cells are:

A) Lymphocytes
B) Granulocytes
C) Monocytes
D) Red blood cells

Correct Answer: C) Monocytes

Q6. After birth, all types of blood cells are formed in:

A) Thymus
B) Adenoids
C) Lymph nodes
D) Bone marrow

Correct Answer: D) Bone marrow

Q7. When a person receives a booster dose of the COVID-19 vaccine, which type of T cell is most directly stimulated?

A) Cytotoxic T cells
B) Memory T cells
C) Helper T cells
D) Suppressor T cells

Correct Answer: B) Memory T cells

Q8. The role of clotting in immunity is to prevent:

A) Loss of blood plasma
B) Entry of pathogens
C) Loss of blood cells
D) Spread of a wound

Correct Answer: B) Entry of pathogens

Q9. Vaccination and disease exposure strengthen:

A) First line of defence
B) Second line of defence
C) Third line of defence
D) Innate immunity

Correct Answer: C) Third line of defence

Q10. Allergy is an overreaction of the immune system to:

A) Harmless substances
B) Harmful substances
C) Pathogens
D) Viruses and bacteria

Correct Answer: A) Harmless substances

Section II: Short Answer Questions

Q1. Enlist the steps of immune response.

The main steps of an immune response are:

1. Recognition: The immune system detects foreign antigens (pathogens) through specific receptors on lymphocytes.

2. Activation: Lymphocytes multiply and differentiate after recognizing the target antigen.

3. Effector Action: Effector cells and antibodies neutralize or destroy the invading pathogen.

4. Memory Formation: Long-lived memory cells remain in the body and provide rapid protection against future infections.

Q2. Draw a flow chart of different types of white blood cells.

White blood cells (leukocytes) are divided into two main groups:

1. Granulocytes

• Neutrophils

• Eosinophils

• Basophils

2. Agranulocytes

• Lymphocytes:

  • B cells

  • T cells:

    • Helper T cells

    • Cytotoxic T cells

    • Suppressor T cells

    • Memory T cells

  • Natural Killer (NK) cells

• Monocytes:

  • Differentiate into macrophages and dendritic cells.

Q3. How do lymph nodes prevent the spread of pathogens in the human body?

Lymph nodes act as biological filtration units along lymphatic vessels. As lymph fluid passes through them, macrophages, dendritic cells, and lymphocytes trap, filter, and destroy foreign particles and pathogens. This prevents infections from spreading throughout the body before the lymph fluid returns to the bloodstream.

Q4. Name a few vaccines and the diseases they control.

Some common vaccines and the diseases they help prevent are:

• BCG Vaccine: Tuberculosis (TB).

• Polio Vaccine (OPV/IPV): Poliomyelitis (polio).

• MMR Vaccine: Measles, mumps, and rubella.

• Hepatitis B Vaccine: Hepatitis B.

Q5. What are the types of memory cells? Why are they important?

There are two main types of memory cells:

1. Memory B cells

2. Memory T cells

Importance: Memory cells can persist in the body for years or even decades after an infection or vaccination. When the same pathogen enters the body again, these cells recognize it quickly and trigger a rapid and strong secondary immune response. This helps protect the body against future infections.

Q6. Why are booster doses of vaccines important?

Immunity levels and antibody concentrations may decrease over time after initial vaccination. A booster dose re-stimulates memory B and T cells, helping restore antibody levels and maintain long-lasting immune protection.

Q7. What are the symptoms of allergy?

Symptoms of allergy vary depending on the allergen and the area of exposure. Common symptoms include:

• Sneezing, runny or blocked nose, and watery, itchy eyes.

• Skin rashes, hives (urticaria), and swelling.

• Wheezing, coughing, shortness of breath, and asthma flare-ups.

• Severe systemic reactions (anaphylaxis), which may cause a dangerous drop in blood pressure and breathing difficulties.

Q8. Name different causes of allergy.

Allergies occur when the immune system overreacts to normally harmless environmental substances called allergens.

Common triggers include:

• Inhalants: Pollen, mold spores, house dust mites, and pet dander.

• Ingestants: Foods such as peanuts, tree nuts, shellfish, milk, and eggs.

• Injectants and Contactants: Insect stings (bees and wasps), latex, certain medications such as penicillin, and cosmetics.

Q9. Which substances cause allergy? Enlist them.

Substances that trigger allergic reactions are called allergens. Common examples include:

1. Tree, grass, and weed pollen.

2. House dust mites and cockroach waste.

3. Animal dander and saliva.

4. Fungal and mold spores.

5. Food proteins, such as peanuts, milk, wheat, soy, and fish.

6. Insect venoms, such as bee and wasp stings.

7. Medications, such as penicillin and aspirin.

8. Contact substances, such as latex and nickel.

Q10. Write the differences between the following.

a. Granulocytes and Lymphocytes

b. Macrophages and Dendritic Cells

c. Allergy and Allergen

d. Cytotoxic T Cells and Helper T Cells

e. Plasma Cells and Memory B Cells

f. Primary and Secondary Immune Response

g. Innate Immunity and Acquired Immunity

Section III: Extensive Answer Questions

Q1. Describe the role of the immune system in the human body.

The immune system is a complex network of cells, tissues, and organs that plays important roles in maintaining the health of the human body.

Its major functions include:

1. Defence Against Pathogens: Protects the body against infections caused by harmful bacteria, viruses, fungi, and parasites.

2. Removal of Cellular Debris: Removes dead, damaged, and ageing cells from body tissues.

3. Tumour Surveillance: Detects and destroys abnormal or mutated cells before they can develop into tumours or cancers.

4. Homeostasis and Healing: Works with inflammatory processes to repair injured tissues and restore normal body functions.

Q2. Explain the immune system and its organs.

The immune system consists of primary and secondary lymphoid organs where immune cells are produced, mature, and carry out their functions.

1. Primary Lymphoid Organs

These organs are responsible for the production and maturation of lymphocytes.

• Bone Marrow: It is the site where all blood cells are produced. B lymphocytes also mature in the bone marrow.

• Thymus Gland: It is the specialized organ where T lymphocytes mature and differentiate.

2. Secondary Lymphoid Organs

These organs provide sites where immune cells encounter antigens and initiate immune responses.

• Lymph Nodes: Filter lymph fluid and contain active lymphocytes and macrophages.

• Spleen: Filters blood, removes old red blood cells, and produces immune responses against pathogens present in the blood.

• Tonsils and Adenoids: Help trap pathogens entering through the respiratory tract.

• Peyer’s Patches and Appendix: Monitor intestinal bacteria and help protect the digestive tract.

Q3. The immune system is made up of white blood cells. What are the different types of white blood cells? Give their roles.

White blood cells, also called leukocytes, are important components of the immune system. They perform different functions to protect the body against infections.

1. Neutrophils

• They are fast-acting phagocytic cells.

• They provide the primary cellular defence against acute bacterial infections.

• They engulf and destroy bacteria and may contribute to pus formation.

2. Eosinophils

• They help combat parasitic infections.

• They also regulate allergic inflammatory responses.

3. Basophils

• They release histamine and heparin during allergic reactions and inflammation.

• Histamine contributes to the inflammatory response.

4. Monocytes

Monocytes can differentiate into macrophages and dendritic cells.

• Macrophages: Engulf and destroy pathogens and cellular debris.

• Dendritic Cells: Capture antigens and present them to T cells, helping connect innate and adaptive immunity.

5. B Lymphocytes

• Produce specific antibodies.

• Antibodies neutralize toxins and help identify pathogens for destruction.

6. T Lymphocytes

T lymphocytes perform different functions:

• Helper T Cells: Coordinate overall immune activity by activating other immune cells.

• Cytotoxic T Cells: Directly destroy infected or cancerous host cells.

7. Natural Killer (NK) Cells

• They target and destroy virus-infected and tumour cells.

• They are part of the innate immune defence.

Q4. Compare innate and adaptive immunity. Which type of immunity increases in most people when they reach adulthood?

Innate and adaptive immunity are two major types of immunity in the human body.

Immunity in Adulthood:

Adaptive immunity increases significantly in most individuals as they reach adulthood. This happens because of cumulative exposure to different environmental pathogens, infections, and vaccinations throughout life.

Q5. Explain the three lines of defence and their components.

The human immune system has three lines of defence that protect the body against harmful pathogens.

1. First Line of Defence (Physical and Chemical Barriers)

The first line of defence consists of non-specific barriers that prevent pathogens from entering the body.

Its components include:

• Intact skin.

• Mucous membranes.

• Ciliated respiratory passages.

• Stomach acid.

• Tears and saliva.

• Sweat.

2. Second Line of Defence (Innate Internal Defences)

The second line of defence consists of non-specific internal mechanisms that act when pathogens cross the first line of defence.

Its components include:

• Phagocytic white blood cells, such as neutrophils and macrophages.

• Natural Killer (NK) cells.

• Inflammation.

• Antimicrobial proteins.

• Fever.

3. Third Line of Defence (Adaptive Immunity)

The third line of defence provides a highly specific response against particular pathogens and antigens.

Its components include:

• T cells.

• B cells.

• Antigen-presenting cells.

• Circulating antibodies.

• Memory cells.

Q6. What is allergy? Explain its types.

Allergy: An allergy is an exaggerated or hypersensitive immune reaction triggered by normally harmless environmental substances called allergens, such as pollen, dust, or certain foods.

Types of Allergic Reactions

1. Immediate (Type I or Anaphylactic) Hypersensitivity

• It is mediated by IgE antibodies.

• It causes rapid release of histamine.

• Examples include hay fever, asthma, hives, and anaphylaxis.

2. Cytotoxic (Type II) Hypersensitivity

• It is mediated by IgG or IgM antibodies.

• These antibodies react with antigens on cell surfaces and may cause cell destruction.

• Example: Blood transfusion reactions.

3. Immune Complex (Type III) Hypersensitivity

• It occurs when antigen-antibody complexes are deposited in body tissues.

• These deposits cause inflammation and tissue damage.

4. Delayed-Type (Type IV) Hypersensitivity

• It is mediated by T cells rather than antibodies.

• The reaction usually appears after 24–72 hours.

• Example: Contact dermatitis caused by poison ivy.

Q7. How has vaccination helped humans eradicate diseases like smallpox?

Vaccination has played an important role in controlling and eradicating infectious diseases.

1. Mechanism of Vaccination

• Vaccines introduce harmless antigens into the body.

• These antigens may come from weakened or inactivated pathogens or their components.

• They stimulate the third line of defence without normally causing the disease.

• The immune system produces memory B and T cells.

• These memory cells provide a faster response if the same pathogen enters the body again.

2. Eradication of Smallpox

Smallpox was eradicated through coordinated worldwide vaccination campaigns led by the World Health Organization (WHO).

The main reasons for its successful eradication were:

• Widespread vaccination helped develop population-level immunity.

• Smallpox infected humans and had no animal reservoir.

• Vaccination campaigns interrupted the transmission of the virus.

• Continued global surveillance helped identify and contain remaining cases.

As a result, smallpox was declared eradicated worldwide in 1980.

Notes by Sir Dilawar
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