Week 8 - Exercise and the Immune system (NOT IN EXAM)

Question 1

What are the two branches of the immune system?

Answer 1

Innate (non-specific) and Adaptive (specific)

Question 2

What is the main role of the immune system?

Answer 2

governs how the body defends against foreign pathogens including viruses (cold, flu), bacteria (pneumonia) + fungi (yeast)

Question 3

A fundamental principle of immunity is being able to recognize what?

Answer 3

“Self” (our own tissues) vs “non-self” and “altered self” (foreign tissues or our own damaged/infected tissues)

Question 4

Where are immune cells produced?

Answer 4

Bone marrow (upper arm)

Question 5

What is the thymus responsible for?

Answer 5

Thymus - primary lymph organ

Its responsible for developing T-cells.

Question 6

Describe the structure of the adaptive (specific) immune system.

Answer 6

Adaptive
- Cell-mediated: T-cells
- Humoral: B-cells

Question 7

Describe the structure of the innate (non-specific) immune system.

Answer 7

Innate
- Humoral: complement cascade
- Cell-mediated: neutrophils, monocytes, natural killer cells
- Physical barriers: Skin, saliva, tears, stomach, mucus

Question 8

What is the difference between cell-mediated immunity and humoral immunity?

Answer 8

Cell-mediated is where cells itself kill the infection whereas humoral is where cells produce certain proteins to kill the infections.

Question 9

What are physical barriers?

Answer 9

They are a branch of innate immune system that physically prevent a foreign substance (microbes) from reaching the site of infection.

Question 10

What are the 3 ways that microbes are stopped?

Answer 10

1) Trapped by skin cells or mucus
2) Killed by antibodies in tears, saliva, and mucus
3) Removed from the body by shedding skin, coughing, vomiting, diarrhoea or flushing bodily fluids (urine/tears)

Question 11

What cells are part of:
a) the innate immune system
b) the adaptive immune system

Answer 11

a) neutrophils, monocytes, natural killers
b) T-cells and B-cells

Question 12

Which two cells kill virus infected cells and tumour cells?

Answer 12

natural killer cells (innate) and T-cells (adaptive)

Question 13

What cells are focused on killing bacteria/virus and tissue repair?

Answer 13

neutrophils, monocytes (innate)
B-cells (adaptive)

Question 14

Innate cell-mediated immunity:

Describe the 3 innate immune cells.

Answer 14

1) Monocytes (3-9% of blood): a type of phagocyte (eating cell) which leaves the blood and form macrophages in tissues. They consume microbes and dead cells by phagocytosis.

2) Neutrophils (60% of blood): most abundant immune cell in the blood. Rapid responder to infection/stress that exits the blood to enter tissues. They engulf microbes (phagocytosis) and kill via the release of toxic molecules (respiratory burst).

3) Natural killer cells (1-6% of blood): destroy virus-infected cells and cancerous cells. They produce proteins such as cytokines to kill infected/transformed cells.

They recognize pathogen associated molecular patterns (PAMPs) - non specific.

Question 15

Innate humoral immunity:

Describe the role of complement proteins, referencing the complement cascade, and the role of cytokines.

Answer 15

Complement proteins are made in the liver and circulate as inactive proteins in the blood. Certain ones can bind to antibodies or patterns on microbes (e.g. bacteria) or dead cells which form complexes that recruit phagocytes to the site via chemical gradients - complement cascade.

Other proteins called cytokines can be released from innate immune cells (natural killer cells) to coordinate the immune response and signal to adaptive immune cells.

Question 16

Why are dendrite cells termed “Antigen presenting cells”?

Answer 16

They process parts of foreign bodies (antigen) and then present the antigen to cells of the adaptive immune system (T and B cells) in lymph nodes - they then remember the virus.

Question 17

What are the two key adaptive immunity cells?

Answer 17

1) T cells (cell-mediated immunity) is a type of lymphocyte developed in the thymus and they release cytokines that kill virus infected cells or tumors.

2) B cells (humoral immunity) is a type of lymphocyte produced in bone marrow. They differentiate into plasma cells and they produce antibodies which coat an infected cell or bacteria and trigger other immune cells to then destroy the cell.

Question 18

Why are T and B cells specific?

Answer 18

When the body re-encounters the same antigen the immune response of T and B cells is based on memory.

Question 19

What are the two types of T-cells in the adaptive immune system (cell-mediated)?

Answer 19

1) Helper T-cells (midfielder)
60-70% of T-cells. They co-ordinate immune response by recruiting other T and B cells to the site of damage/infection.

2) Cytotoxic T-cells. (Haaland)
30-40% of T-cells. They are highly efficient, specific killers and they recognise antigens on the surface of damaged or infected cells or tumours.

Question 20

What are regulatory T-cells?

Answer 20

4% of Helper T-cell population and they have a role in suppressing the activity of the immune system.

“CB - They calm it down”

Question 21

What are 4 the different ways we can measure immune function?

Answer 21

1) Self-reported illness: upper respiratory tract infections - number and severity

2) Cellular level: concentration of immune cells (T-cells, neutrophils, B-cells), measure immune cell function (e.g. movement of immune cells towards bacteria/virus)

3) Release of molecules reflecting immune response: antibodies with anti-microbial properties, enzymes with a role in phagocytosis

4) In vivo immunity: antibody response to a vaccine (Flu, Hepatitis B), wound healing

Question 22

What immune response does moderate intensity exercise evoke? How does this differ with intense exercise?

Answer 22

It increases the number of leukocytes (WBC) in the blood.

This increase is greater during and in the minutes after intense exercise, but leukocyte levels drop below rest in the hours after intense exercise.

Question 23

What was the “Open window for infection” Hypothesis?

Answer 23

refers to the period after exercise (up to 3hrs) where blood leukocytes were below resting levels so we were at greater risk of infection - we now know its because they migrate to sites in the body which can be susceptible to damage/infection

Question 24

Describe the mechanisms responsible for driving immune cell mobilisastion during exercise.

Answer 24

Exercise increases shear stress, sympathetic drive/vasoconstriction and adrenaline concentrations that demarginate (move) immune cells into peripheral blood - explains increases in leukocytes during exercise.

Effector immune cells are preferentially mobilized (effector T-cells and natural killer cells).

Question 25

Where are immune cells redistributed after exercise?

Answer 25

they migrate from the blood to sites where the body may encounter damage or infection (e.g. muscle, lungs or gut) - known as immunosurveillance.

This explains the drop in immune cells in the blood after exercise!

Question 26

Why do cells mobilized into the blood during exercise (T-cells and natural killer cells) have the highest capacity to leave the circulation?

Answer 26

because they have the highest function and tissue homing potential

Question 27

What is the response to exercise-induced muscle tissue injury?

Answer 27

A strong innate immune response which involves neutrophils, monocytes and macrophages.

Question 28

In response to exercise-induced muscle tissue injury, innate immune cells release proteins. How do they initiate, mediate and terminate muscle repair?

Answer 28

… by modulating processes such as:

1) Movement of immune cells into the muscle (migration)
2) Muscle fiber breakdown and regeneration
3) Anti-microbial defence

Question 29

Describe the exercise-induced mobilisation of immune cells during exercise and after exercise.

Answer 29

During exercise and immediately after exercise, there is an increase in immune cells in the blood. After exercise (hours after), they migrate to sites of potential damage or infection (muscle, lungs, or gut).

Question 30

What are 3 direct improvements in immunity as a result of exercise?

Answer 30

• ↓ number of infections
• ↓ severity of infections
• ↑ antibody production
• ↑ response to vaccination
• ↑ wound healing
• ↑ surveillance of cancer cells

Question 31

What are 3 indirect improvements in immunity as a result of exercise?

Answer 31

• ↑ weight loss (adipose tissue), thus ↓inflammation
• Improved vasculature health and thus immune cell recirculation
• ↑ anti-inflammatory blood profile

Question 32

How can regular physical activity impact the immune system in older and clinical populations?

Answer 32

• It can offset the natural decline in immunity with age.
• It may also improve immunity in people with autoimmune, cardiovascular, neurological and metabolic illness.

Question 33

Why may moderate amounts of exercise enhance immune function but heavy training load impair immune function?

Answer 33

Heavy training load:
- Less antibodies
- Reduced immune cells
- Less responsive immune cells
- Reduced function of immune cells
- Poorer redistribution of immune cells

Question 34

Name 3 lifestyle factors that can have a negative impact on immune function.

Answer 34

1. Inadequate nutrition.
2. Poor sleep habits.
3. Mental stress.

Question 35

What does the J-shaped relationship between the intensity of exercise and the risk of URTI (upper resipiratory tract infection) suggest?

Answer 35

suggests that the risk of URTI is lowest in people who engage in moderate exercise and highest in people who engaged in vigorous exercise

Question 36

During exercise recovery, why do some immune cells move from the blood to muscle tissue?

Answer 36

• To promote an inflammatory response
• To recruit other immune cells through the release of cytokines
• To survey potential damage to active skeletal muscle