secondary non specific defence against pathogens

Question 1

How does the body recognise invading pathogens?

Answer 1

By its antigens (proteins, polypeptides, polysaccharides)

Question 2

Allergic response

Answer 2

Mast cells are involved in the allergic response

Antibodies to the allergen bind to mast cells and the allergen

Causes the mast cells to release chemicals (e.g. histamines) which causes the allergy symptoms

Question 3

Secondary defences

Answer 3

act on pathogens that have entered the body

Question 4

Opsonins

Answer 4

Chemicals

bind to pathogens (their antigens) to tag them making them more recognisable to phagocytes

Act as binding sites for phagocytic cells –> more easily bind and engulf the pathogen

Question 5

Fever

Answer 5

Normal body temperature for humans is around 37°C

Maintained by the hypothalamus in your brain

When a pathogen invades your body, cytokines stimulate your hypothalamus to reset your thermostat to a higher level, casing your temperature to go up

- most pathogens reproduce best at 37°C so higher temperatures will restrict their reproduction 

- the specific immune system works faster at higher temperatures

Question 6

Inflammation

Answer 6

Symptoms : redness, pain, swelling, heat

Occurs because of cellular activity and chemical defences employed in the bloods

Question 7

stages of inflammation

Answer 7

Mast cells found throughout the body

Respond to damage by secreting histamine and cytokines

Histamine, cell-signalling compound that causes, increased blood flow through capillaries; capillaries become leaky allowing fluid, white blood cells & some proteins to leave and enter tissues, causing swelling

Cytokines attract phagocytes

Phagocytes leave the blood, enter tissues, engulf any foreign material

Question 8

Phagocytosis

Answer 8

Specialised white blood cells that engulf and destroy pathogens

e.g. neutrophils – most common type, produced in the bone marrow, lobed nucleus (change shape–> fit through capillaries), released in large numbers in response to an infection but are short-lived & die after digesting a few pathogens) ; dead neutrophils may form pus

Question 9

stages of phagocytosis

Answer 9

Phagocytes are attracted by chemical produced by pathogens or tissues (histamines and cytokines)

Phagocytes recognise the pathogen as non-self

Phagocyte engulfs the pathogen and encloses it in a vacuole called a phagosome

Phagosome fuses with a lysosome to form a phagolysosome

Enzymes from the lysosome digest and destroy the pathogen and the products are absorbed

Question 10

Lymph

Answer 10

Excess tissue fluid drains into the lymph vessels

Pathogens in tissue fluid can enter lymph

Pathogens are transported along the lymph system to lymph nodes( in head, neck, armpits, groin)

Activity of phagocytes (and lymphocytes) causes swelling of lymph nodes

Question 11

Macrophages

Answer 11

A phagocyte produced in the bone marrow

Travels in the blood(as monocyte) and settles in the body tissue(As monocyte), particularly in the lymph nodes

the largest leucocyte

Kidney-shaped nucleus