Week 8 - Exercise and the Immune system (NOT IN EXAM) Flashcards
What are the two branches of the immune system?
Innate (non-specific) and Adaptive (specific)
What is the main role of the immune system?
governs how the body defends against foreign pathogens including viruses (cold, flu), bacteria (pneumonia) + fungi (yeast)
A fundamental principle of immunity is being able to recognize what?
“Self” (our own tissues) vs “non-self” and “altered self” (foreign tissues or our own damaged/infected tissues)
Where are immune cells produced?
Bone marrow (upper arm)
What is the thymus responsible for?
Thymus - primary lymph organ
Its responsible for developing T-cells.
Describe the structure of the adaptive (specific) immune system.
Adaptive
- Cell-mediated: T-cells
- Humoral: B-cells
Describe the structure of the innate (non-specific) immune system.
Innate
- Humoral: complement cascade
- Cell-mediated: neutrophils, monocytes, natural killer cells
- Physical barriers: Skin, saliva, tears, stomach, mucus
What is the difference between cell-mediated immunity and humoral immunity?
Cell-mediated is where cells itself kill the infection whereas humoral is where cells produce certain proteins to kill the infections.
What are physical barriers?
They are a branch of innate immune system that physically prevent a foreign substance (microbes) from reaching the site of infection.
What are the 3 ways that microbes are stopped?
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)
What cells are part of:
a) the innate immune system
b) the adaptive immune system
a) neutrophils, monocytes, natural killers
b) T-cells and B-cells
Which two cells kill virus infected cells and tumour cells?
natural killer cells (innate) and T-cells (adaptive)
What cells are focused on killing bacteria/virus and tissue repair?
neutrophils, monocytes (innate)
B-cells (adaptive)
Innate cell-mediated immunity:
Describe the 3 innate immune cells.
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.
Innate humoral immunity:
Describe the role of complement proteins, referencing the complement cascade, and the role of cytokines.
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.
Why are dendrite cells termed “Antigen presenting cells”?
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.
What are the two key adaptive immunity cells?
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.
Why are T and B cells specific?
When the body re-encounters the same antigen the immune response of T and B cells is based on memory.
What are the two types of T-cells in the adaptive immune system (cell-mediated)?
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.
What are regulatory T-cells?
4% of Helper T-cell population and they have a role in suppressing the activity of the immune system.
“CB - They calm it down”
What are 4 the different ways we can measure immune function?
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
What immune response does moderate intensity exercise evoke? How does this differ with intense exercise?
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.
What was the “Open window for infection” Hypothesis?
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
Describe the mechanisms responsible for driving immune cell mobilisastion during exercise.
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).
