immunity lowkey

Question 1

What are the types of non-cellular pathogens?

Answer 1

Viruses and prions

Question 2

Give two examples of physical barriers in plants

Answer 2

Waxy cuticles on leaves to prevent pathogenic entry.
Presence of thorns or trichomes to deter insects and grazers.

Question 3

Give two examples of chemical barriers in plants

Answer 3

Oxalic acid, toxic to some organisms if ingested.
Chitinases, enzymes that have antifungal properties.

Question 4

Give two examples of physical barriers in animals

Answer 4

Intact layer of dead skin which prevents pathogens from infecting live cells.
Mucus secretions which trap pathogens and prevent orificial entry.

Question 5

Give two examples of chemical barriers in animals

Answer 5

Lysozymes in tears have antibacterial properties and prevent bacterial invasion.
Stomach acid, very low pH destroys many pathogens by denaturing the functional tertiary structures of their essential enzymes.

Question 6

What are phagocytes and how do they work?

Answer 6

Phagocytes are leukocytes that engulf non-self cells by endocytosis and digest them using lysosomes.

Question 7

What are the three types of phagocytes?

Answer 7

Neutrophils, Macrophages, Dendritic cells.

Question 8

What are cytokines?

Answer 8

Cytokines are signalling molecules that stimulate, recruit, and proliferate immune cells and guide them to sites of infection or injury.

Question 9

What are macrophages?

Answer 9

Macrophages are phagocytes that engulf pathogens and display pathogenic antigens on their surface MHC II markers.

Question 10

What are the three types of antigen presenting cells?

Answer 10

Macrophages, B- cells and dendritic cells.

Question 11

What are dendritic cells?

Answer 11

Dendritic cells are phagocytes that engulf pathogens and display pathogenic antigens on their surface MHC II markers.

Question 12

What are natural killer cells?

Answer 12

Natural killer cells are immune cells that identify and destroy abnormal or cancerous cells by detecting missing/abnormal MHC I markers on their surface.

• found in blood/lymph
• kill virus-infected cells

Question 13

What are interferons?

Answer 13

Interferons are cytokines released from virally infected cells that interact with receptors on normal cells and make them less susceptible to viral infection.

• signal change in plasma membrane making entry of virus more difficult (make PM less fluid)
• signals neighbouring uninfected cells to prepare to destroy RNA to reduce protein synthesis
• signal neighbouring infected cells to undergo apoptosis
• activates immune cells such as NK cells

Question 14

What are the three major outcomes of a complement cascade?

Answer 14

Opsonisation, Chemotaxis, Lysis

Question 15

What is a complement cascade?

Answer 15

A complement cascade is activated when they make direct contact with molecules on the surface of pathogens
- it is a series of complex reactions where complement proteins interact with each other to deal with pathogens, and can result in opsonisation, chemotaxis, or lysis

Question 16

Describe the process of opsonisation.

Answer 16

Opsinisation occurs when antibodies or complement proteins stick to the surface of pathogens flagging them for phagocytosis.

Question 17

Describe the process of chemotaxis.

Answer 17

Chemotaxis is the process of complement proteins gathering near pathogens to attract phagocytes to them, increasing the chances of phagocytosis

Question 18

Describe the process of lysis with respect to complement proteins.

Answer 18

Lysis occurs when complement proteins join together and form a membrane attack complex (MAC), which creates membranal pores and destroys the pathogen cell.

Question 19

What are the three main stages of inflammation?

Answer 19

1. Initiation
2. Vasodilation
3. Migration

Question 20

What occurs during vasodilation with respect to inflammation?

Answer 20

During vasodilation, histamine released from mast cells causes blood vessels to dilate and increases blood flow to injury site, which can cause swelling, redness and warmth associated with inflammation.

Question 21

What occurs during migration with respect to inflammation?

Answer 21

During migration, phagocytes are guided by cytokines to the site of injury and complement proteins opsonise pathogens to increase chances of phagocytosis, platelets travel to the site to block wounds → important for clotting,

• pus indicates that this stage is occurring
  –> consists of mainly dead immune cells, tissue and pathogens

Question 22

What are the three main roles of the lymphatic nervous system?

Answer 22

• Transportation of antigen-presenting cells to secondary lymphoid tissues for antigen recognition and initiation of the adaptive immune response.
• Production of leukocytes
• Removal of fluid from tissues around the body.

Question 23

What are the three major components of the lymphatic nervous system?

Answer 23

• Primary lymphoid tissues
• Secondary lymphoid tissues
• Lymphatic vessels

Question 24

Where are B and T cells produced?

Answer 24

B and T cells are produced in primary lymphoid tissues found in bone marrow.

Question 25

What are the main secondary lymphoid tissues?

Answer 25

• Lymph nodes
• Spleen

Question 26

What are the main primary lymphoid tissues?

Answer 26

• Bone marrow
• The thymus

Question 27

How is the adaptive immune response initiated?

Answer 27

The adaptive immune response is initiated by:
- the selection of T-helper cells
→ phagocytosis occurs and the antigen-presenting cell displays the specific pathogenic antigens on their surface via MHC II markers to activate corresponding T-helper cells
- This can lead to either the humoral or cell-mediated immune responses.

Question 28

brief outline of the humoral immune response.

Answer 28

1. Antigen presenting cells display pathogenic antigens on their cell surface to activate helper T-cells and initiate the humoral immune response.
2. Helper T release cytokines activating B cells which bind to the same antigen in secondary lymphoid tissues and express them via MHC II markers on their surface.
3. Selected helper T-cells recognise and bind to the selected B cell and release cytokines to make the B cell undergo clonal expansion and differentiate into either plasma or B memory cells.
4. Plasma cells produce antibodies specific to the selected antigen, and are secreted into the bloodstream to defend against the pathogen. Memory B cells remain in lymphoid tissues and can divide into plasma cells if reinfection occurs.

Question 29

What is the function of plasma cells?

Answer 29

Plasma cells produce antibodies that are specific to the antigen that activated their B cell and helper T cell, which get secreted into the blood to defend against extracellular pathogens and other foreign material.

Question 30

What is the function of memory B cells?

Answer 30

Memory B cells provide long-lasting immunity and remain in lymphoid tissues for long periods of time while releasing low amounts of antibodies, and can also rapidly divide into plasma cells if reinfection occurs for a faster adaptive immune response.

Question 31

What are the cellular components of the second line of defense?

Answer 31

Neutrophil, macrophage, dendritic cell, natural killer cell, mast cell, eosinophil cells

Question 32

Outline how natural killer cells detect and destroy pathogenic cells.

Answer 32

1. Killer activation receptors on natural killer (NK) cells bind to cellularly stressed cells.
2. Killer inhibitory receptors examine the cell’s surface for MHC I markers to bind to.
3. If there are insufficient MHC I markers on the cell, killer inhibitory receptors cannot bind and cell death is initiated via apoptosis.

Question 33

Outline the cell-mediated immune response.

Answer 33

1. Antigen presenting cells display pathogenic antigens on their surface via MHC II markers to activate helper T-cells, while simultaneously they encounter a naive T-cell with matching antigens.
2. The selected T-cell is stimulated by cytokines to undergo clonal expansion and differentiate into cytotoxic T cells and memory T cells.
3. Cytotoxic T cells can recognise abnormal proteins on infected cells, destroying them by secreting chemicals to induce apoptosis.
4. Memory T cells provide long lasting immunity and remain in lymphoid tissues and can rapidly divide into helper and cytotoxic T cells if the pathogen is re-encountered for a faster adaptive immune response.

Question 34

What is artificial immunity?

Answer 34

Artificial immunity is immunity conferred through medical intervention.

Question 35

What is active immunity?

Answer 35

Active immunity is immunity conferred by antibodies and memory cells produced by one’s own adaptive immune system.

Question 36

What is the role of the first line of defence?

Answer 36

The first line of defence is responsible for preventing or impeding the entry of a pathogen into an organism

Question 37

Why is the adaptive immune response slower than the innate immune response?

Answer 37

The adaptive immune response is slower than the innate immune response because it requires time to recognize specific pathogens, activate specialized immune cells and form immunological memory for a precise response. In contrast, the innate immune system is active all the time and provides immediate but nonspecific defence

Question 38

Outline the process of becoming allergic.

Answer 38

1. Allergen is ingested or inhaled and recognised as non-self by the immune system.
2. The adaptive immune system activates and B cells produce IgE antibodies.
3. IgE antibodies attach to mast cells, priming them and sensitising the individual to the allergen.
4. During reexposure to the allergen, the mast cells are triggered and release lots of histamine which results in an inflammatory response.