session 8 - immune system

Question 1

The second line of defence:

Internal defences are provided by? and occurs when?

Answer 1

• Antimicrobial substances • Natural killer cells • Phagocytes • Inflammation • Fever occurs when first line of defence has been breached

Question 2

Antimicrobial substances that discourage microbial growth are?

Answer 2

• Interferons • Complement system • Iron-binding proteins • Antimicrobial proteins

Question 3

Interferons (IFNs)

Answer 3

Produced by lymphocytes, macrophages, and fibroblasts infected with viruses. •Interfere and stop viral replication.

Question 4

Complement system

Answer 4

A group of about 30 inactive proteins present in blood plasma and on plasma membranes •when activated, these proteins “complement” or enhance certain immune, allergic, and inflammatory reactions.

Question 5

Iron-binding proteins

Answer 5

Inhibit growth of certain bacteria by reducing amount of available iron The following are Antimicrobial substances that bind to iron so the iron is no loner free for bacteria to bind to - therefore cannot grow and divide •Transferrin: in blood and tissue fluids •Lactoferrin: in milk, saliva, and mucus •Ferritin: in the liver, spleen, and red bone marrow •Haemoglobin: in red blood cells

Question 6

What is innate immunity?

Answer 6

Non specific ( e.g will defend against any bacteria, not specific! ), We have the ability to produce from birth

Question 7

Natural killer cells - what are they? where are they found? function?

Answer 7

• cytotoxic lymphocyte
• Present in blood, spleen, lymph nodes and red marrow

Function

• kill a wide variety of microbes and tumour cells
• attack any body cells that display abnormal or unusual plasma membrane proteins and cause cytolysis or induce apoptosis
• kill infected cells and release microbes to be destroyed by phagocytes

Question 8

Phagocytes are.. and the 2 major types

Answer 8

cells that ingest microbes (cells) or other particles such as cellular debris ( cells that eat cells)

•Neutrophils - most abundant white blood cells we have

When they go up they are a really good indicator that there is a bacterial infection

•Macrophages (developed from monocytes)

–fixed macrophages stand guard in specific tissues

• In the skin, liver, lungs, brain, spleen, red marrow and lymph nodes

–wandering macrophages are in most tissues

Question 9

The five phases of phagocytosis

Answer 9

1. Chemotaxis, - recognition
2. Adherence - bind to
3. Ingestion - eat
4. Digestion - break down of bacterial components (internalised)
5. Killing

Question 10

Phagocytosis

1.Chemotaxis:

Answer 10

a chemically stimulated movement of phagocytes to a site of damage

• chemicals from invading microbes, white blood cells, damaged tissue cells, or activated complement proteins

Question 11

Phagocytosis

2. Adherence:

Answer 11

Attachment of the phagocyte to the microbe or other foreign material

• Enhanced by the binding of complement proteins to the invading pathogens

Question 12

Phagocytosis

3. Ingestion:

Answer 12

a process of engulfing the microbe

• Caused by pseudopods which in turn merge to form phagosomes.

Question 13

Phagocytosis

4. Digestion:

Answer 13

• Lysozyme, which breaks down microbial cell walls
• Other digestive enzymes that degrade carbohydrates, proteins, lipids, and nucleic acids.
• Lethal Oxidants produced by phagocytes such as
• superoxide anion (O2–),
• Hydrogen peroxide (H2O2)

*combined with Lysozymes will break down microbe*

Question 14

Phagocytosis

5. Killing:

Answer 14

The chemical attack of lysozyme, digestive enzymes, and oxidants will quickly lead to the death of microbes.

o A microbe may evade (escape, avoid) phagocytosis through:

• capsule formation, - can form a capsule to prevent the action of lysozymes
• toxin production, - toxins desgined to kill the cells that are trying to kill them
• interference with lysozyme secretion,
• microbe’s ability to counter oxidants produced by the phagocytes.

Question 15

Describe Inflammation

What is it’s function and what causes it

Answer 15

a nonspecific, defensive response of the body to tissue damage

oFunction:to trap microbes, toxins or foreign material and begin tissue repair

oInitiated by damaged cells due to:

• Pathogens - viruses and bacteria
• Abrasions - blisters etc
• Chemical irritations - strong chemicals burning skin
• Distortion or disturbances of cell
• Extreme temperatures

Question 16

signs and symptoms of inflammation

Answer 16

Vasodilation and increased permeability of vessels:
• caused by histamine, prostaglandins, leukotrienes from variety of cells

Occurs within minutes producing

• Redness
• Heat

. Oedema

• Swelling
• Pain can result from injury, pressure from oedema or irritation by toxic chemicals
• Loss of function depending on the site and extent of the injury. ( e.g rolled ankle )

Question 17

What are the 3 basic Stages of Inflammation

Answer 17

1. Vasodilation and increased permeability of blood vessels,
2. Emigration (movement) of phagocytes from the blood into interstitial fluid,
3. Tissue repair

Question 18

Stage 1 of inflammation

Answer 18

1. Vasodilation and increased permeability of vessels:

o Vasodilation:

• allows more blood to flow through the damaged area,
• helps remove microbial toxins and dead cells.
• Redness and heat is a function of vasodilation and permeability due to increase of blood flow

oIncreased permeability:

• permit the substances to pass from the blood vesselsthat normally retained in blood
• permits defensive proteins such as antibodies and clotting factors to enter the injured area from the blood
• Swelling occurs when the body is helping get all the white blood cells and antibodies out of the blood and into the tissue. We are also getting a lot of plasma coming out into our tissues and that’s the basis of our swelling.

Question 19

Stages of inflammation

2. Phagocyte emigration

Answer 19

• within an hour, neutrophils and then monocytes arrive and leave blood stream (emigration) to reach the damaged area.

Question 20

Stages of Inflammation

What is stage 3

Answer 20

Tissure Repair

Question 21

Symptoms of inflammation: what causes vasodilation and capillary permeability ?

and what are the symptoms

Answer 21

caused by histamine, prostaglandins, leukotrienes being released from a variety of cells
• Occurs within minutes producing

• heat, redness and oedema
• pain can result from injury, pressure from oedema or

irritation by toxic chemicals

Question 22

What is Fever and when does it occur

Answer 22

An abnormally high body temperature that occurs because the hypothalamic thermostat is reset

o Occurs during infection and inflammation
o Bacterial toxins trigger release of fever-causing cytokines such as interleukin-1 from macrophages

o Significance of the release of interleukin-1 and fever:

• Intensifies effects of interferons

• Inhibits bacterial growth
• Speeds up tissue repair

Extra notes for understanding:

Question 23

What is adaptive specific immunity and its properties ?

Answer 23

The ability of the body to defend itself against specific invading agents such as bacteria, toxins, viruses, and foreign tissues.

oProperties: Differs from nonspecific defense mechanisms

• Specificity: specific for particular foreign molecules (antigens) and recognize self and non-self
• Memory: Remembers most previously encountered antigens so that a second encounter produces an even more vigorous response

Question 24

What are the 2 types of Adaptive (Specific) immunity?

Answer 24

o Antibody Mediated Immunity (AMI) / Humoral Immunity

• Mediated by B Cells ( type of lymphocyte, made in bone marrow )

• Antibodies mediating the immune response to an antigen

o Cell Mediated Immunity (CMI)

• Mediated by T Cells ( made in bone marrow, matures in thymus)

• cells killing cells

Question 25

Cell mediated immunity refers to?

Answer 25

refers to destruction of antigens by T cells.

– killer T cells attack antigens
– helper T cells co-stimulate T and B cells

• CMI always involves cells attacking cells.
• Effective against intracellular pathogens, such as fungi, parasites, and viruses; some cancer cells; and foreign tissue transplants.

Question 26

Define Antibody-mediated (humoral) immunity

Answer 26

• destruction of antigens by antibodies.

– B cells transform into plasma cells,
– Plasma cells synthesize and secrete specific proteins called antibodies

• works mainly against antigens dissolved in body fluids (humors) and extracellular pathogens.
• Effective against bacteria that multiply in body fluids but rarely enter body cells.

For better understanding: Plasma cells are a type of B cells that sit in your lymph node continuously making antibodies that will spill out into your lymph fluid and into your cardiovascular system and will be out there picking up all the specific antigens that they have been made against.

Effective against extracellular Bacteria (bacterial virus) that get into our blood , our respiratory system and our tissues. Antibodies are effective in getting to the places.

Question 27

Explain Maturation of T Cells and B Cells and immunocompetance

Answer 27

o B and T Lymphocytes: The cells of specific immunity

o Maturation:

Derived from: Pluripotent stem cells in red bone marrow

B cells: complete their development in red bone marrow.

T cells: mature in thymus.

o Immunocompetance: Before T cells leave the thymus or B cells leave bone marrow, they acquire several distinctive surface proteins; some function as antigen receptors - molecules capable of recognizing specific antigens.