The Immune System

Question 1

Features of innate immune system

Answer 1

• Always active
• Does not require time for activation
• Response is non-specific to any pathogen

Question 2

Mucus

Answer 2

Traps potential pathogens, preventing their entry into the body

Question 3

Skin

Answer 3

Acidic skin secretions inhibit growth of harmful bacteria on skin

Question 4

Tears & Saliva

Answer 4

Contain lysozymes that kill bacteria

Question 5

Defensins

Answer 5

Microcidal molecules secreted by skin and mucous membranes

Question 6

Natural killer cells

Answer 6

Kills human cells that are infected or malignant

Question 7

Dendritic cells

Answer 7

Phagocytes found in lymph nodes; APC

Question 8

Phagocytes

Answer 8

Type of white blood cell that can engulf and digest microorganisms, remove dead cells, and boost immune responses

Question 9

MHC Class I molecule

Answer 9

• Found on all healthy nucleated cells
• Displays peptide antigens in cytoplasm of infected human cells
• Antigen-MHC Class I complex recognized by cytotoxic T cells which kill the target cells

Question 10

MHC Class II molecules

Answer 10

• Only found on the surface of APCs
• Displays antigens from pathogens digested by APC during phagocytosis
• Antigen MHC Class II complex recognised by helper-T cell

Question 11

Features of adaptive immune system

Answer 11

• Highly specific to the particular pathogen that induced it
• Immunological memory
• Defends against immune system consists of B & T lymphocytes

Question 12

Immunological memory

Answer 12

The adaptive immune response increases in magnitude with each subsequent exposure to a particular pathogen

Question 13

Helper T cells (CD4⁺ cells)

Answer 13

• Regulates activities of other immune cells via secretion of cytokines
• Express both specific T cell receptors and CD4 receptors

Question 14

Cytotoxic T cells (CD8⁺ cells)

Answer 14

• Identifies and kills abnormal human cells in the body
• Express both specific T cell receptors and CD8 receptors

Question 15

B lymphocytes

Answer 15

• Immature B cells arise from blood stem cells in bone marrow
• Naive B cells differentiate to effector plasma cells or memory B cells

Question 16

Function of antibodies

Answer 16

• Precipitation
  turns soluble antigens insoluble
• Agglutination
  Links cell bound antigens together, causing clumps
• Neutralisation
  Masks dangerous parts of pathogens
• Inflammation
  Triggers histamine release
• Complement
  Complement protein perforates cell membrane

Question 17

Somatic recombination

Answer 17

Rearrangement of antigens’s amino acid sequence to confer different antigen specificity

Question 18

Active immunity

Answer 18

• From exposure to a pathogen or vaccine activates the adaptive immune system to produce antibodies
• Provides long term protection due to production of memory cells

Question 19

Passive immunity

Answer 19

• Provided when a person is given antibodies (rather than producing it themselves)
• Shorter team protection as antibodies are eventually broken down and are not replenished naturally