5. Strategies of Defence against Pathogens Part 2

Question 1

What are non-specific (innate) immune responses?

Answer 1

General defences to attack anything that doesn’t belong.

Question 2

What is the role of the tissue/interstitial fluid of the lymphatic system and where does the fluid go?

Answer 2

Bathes the tissues and cells, supplying them with nutrients and O2, and removes waste.
-Some tissue fluid returns directly into the capillaries, but some drain back into the blood circulation through a network of lymphatic vessels (called lymph and contains leucocytes (WBC), pathogens and cell debris)

Question 3

What are the 2 roles of the lymphatic system?

Answer 3

1. Returns proteins that leak out of the blood, back into the blood
2. Role in defence (continuous movement of WBC allow for a routine screen of the body for foreign material)

Question 4

What are lymph nodes and what is their role in the lymphatic system?

Answer 4

Clumps of lymph tissue at particular locations, which filters lymph and traps foreign particles in fibres to be dealt with.

Question 5

What is the role of the spleen in the lymphatic system?

Answer 5

Stores and releases blood, and destroys blood-borne pathogens.

Question 6

What are tonsils?

Answer 6

Lymph tissue at the back of the throat, which is an ideal spot to combat pathogens.

Question 7

Where is the thymus gland located?

Answer 7

Near heart, T lymphocyte maturation.

Question 8

What is bone marrow?

Answer 8

Generation of B&T lymphocytes.

Question 9

What are white blood cells? Give an example:

Answer 9

Called leucocytes, possess a nucleus, and are manufactured in the bone marrow.
Eg. Platelets

Question 10

What is an antigen?

Answer 10

Anything that triggers an immune response.
-Foreign molecules on either the outer surface of invaders, or the toxins or enzymes they secrete, trigger immune responses.

Question 11

Describe an innate response:

Answer 11

• Work for any disease/invader regardless of their type
• Not something learned (past experience will not change the response for next time)
• Similar in both plants and animals

Question 12

What is inflammation and list the 2 main ways it is triggered:

Answer 12

A complex process involving many different cell types and signaling molecules, characterised by swelling, redness, heat, and pain.
Main ways it is triggered:
-Macrophage initiated inflammation
-Cell damage initiated inflammation

Question 13

Describe the location and function of macrophage initiated inflammation:

Answer 13

• White blood cells (WBC) (macrophages or dendritic cells) are strategically distributed throughout all body tissues, particularly skin, lymph, lungs, liver, spleen, and kidneys.
• Act as sentinels to check everything passing by, engulf foreign material, and produce signal molecules called cytokines
• Different cytokines depending on the job (these include interferons and interleukins)

Question 14

What is cell damage initiated inflammation stimulated by and what does it release?

Answer 14

Mast cells can be stimulated by ruptured body cells and release histamine, as can circulating white blood cells (WBC) call basophils.

Question 15

Describe what happens cell damage initiated inflammation is activated:

Answer 15

• When activated, WBC (leukocytes) migrate into the region due to chemotaxis (following the source of the chemical signaling molecules)
• Leukocytes (monocytes and neutrophils) come to the area and phagocytose foreign material
• Neutrophils are short-lived and die in a few days to prevent the risk of being infected and spreading disease around the body, which is why infected sites often accumulate pus (dead neutrophils)

Question 16

What is the role of histamine in cell damage initiated inflammation?

Answer 16

Promotes vasodilation in tissues (increases blood flow), and increases the permeability of capillaries so WBC can squeeze out intracellular fluid more easily.
-Histamine is produced by mast cells

Question 17

Describe how fever and pain are caused:

Answer 17

• Some interleukins released by macrophages signal the hypothalamus (temperature regulator in the brain)
• The hypothalamus resets body temperature to higher than normal (Eg. 39˚), which can restrict the functioning and reproduction of many pathogens (above optimum temperatures for their enzymes)
• Some cytokines also cause drowsiness, allowing the body to save its energy to fight invaders and repair damaged tissue

Question 18

List the 4 ways complement proteins can act:

Answer 18

• Binding to the surface of bacteria and yeast to tag for detection and uptake by phagocytes
• Inducing chemotaxis
• Stimulate mast cells to release histamine
• Membrane attack complex- form a structure to puncture membranes

Question 19

What are interferons and what happens when they signal neighbouring cells?

Answer 19

Are released by virus infected cells and act as a warning signal from the doomed cell to its neighbours.
-Neighbours cause changes to the surface of surrounding cells to help prevent infection and induce the expression of virus resistance genes.

Question 20

What is the concept of the rational drug design? Give an example:

Answer 20

Based on the knowledge of how the structure of a virus (or other pathogens), enables it to cause disease or complete its life cycle and then designing a molecule that will block a critical enzyme or receptor.
Eg. The swine flu vaccine works by blocking just one antigen which allows the virus to leave the cell. (know Relenza example)

Question 21

List the 5 things which make up the innate immune response:

Answer 21

• Phagocytes
• Inflammation
• Interferons
• The complement system
• Natural killer cells

Question 22

What is the complement system?

Answer 22

A system of numerous proteins that have various functions in the body, such as sticking to cells that have antibodies attached to them, which help the leucocytes in various ways.

Question 23

What are the structural changes of inflammation and why do they occur?

Answer 23

Local swelling caused by dilation of arterioles leading to the infected area and increased permeability in the walls of these blood vessels, which make the blood vessels ‘leaky’.
-This allows phagocytes to more easily move out of the blood and into the site of infection
It also causes local swelling (due to increased fluid leaking out of the blood vessels) and redness and heat (caused by the increased blood flow to the area resulting from the dilation of arterioles).
-Thes effects are caused by the actions of a cytokine called histamine, which is released by mast cells in response to local damage.