Exercise and the immune system (wk10) Flashcards
The physical, cellular and chemical components of the innate and adaptive immune system
-Physical barriers
-Physical barriers -> Physical barriers are a branch of the innate immune system that ‘physically’ prevent a foreign substance from reaching the site of infection. Microbes can be:
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)
Draw the graph for the immune system
-Including adaptive and innate
Describe the cellular components
-Cell-mediated (called white blood cells or leukocytes)
- Monocytes (3-9% of blood) – A type of phagocyte (‘eating cell’) for microbes and dead cells. Leave the blood and form macrophages in tissues.
- Neutrophils (60% of blood) – A rapid responder to infection/stress that exits the blood to enter tissues. Engulf microbes (phagocytosis) and kill via the release of toxic molecules (respiratory burst)
- Natural killer cells (1-6% of blood) – Destroy virus-infected cells and cancerous cells. Produce proteins, such as ‘cytokines’ to kill infected/ cancerous cells.
Describe innate immune cells
Innate immune cells recognise pathogen associated molecular patterns (PAPs) – non-specific
-Innate immunity: Humoral ->
* Complement proteins are made in the liver bind to antibodies or PAMPs on microbes (e.g. bacteria) or dead cells
* These proteins form complexes that recruit phagocytes to the site via chemical gradients (complement cascade)
* Other proteins called cytokines can be released from innate immune cells to kill infected cells or signal to the adaptive immune system
Describe bridging innate and adaptive immunity (dendritic cells)
-Include T and B cells
-Bridging innate and adaptive immunity (dendritic cells) -> Dendritic cells process parts of a foreign bodies and present the antigen to cells of the adaptive immune system (T and B cells) in lymph nodes. Dendritic cells are termed antigen presenting cells. Also known as an alarm cell as it can recognise infections and send signals and recruit the adaptive immune system to help quickly.m
-Adaptive immunity ->
* T cells (cell-mediated immunity)
- A type of lymphocyte developed in the thymus (20-40% of blood)
- T cells release cytokines that kill virus infected cells or tumours
- These responses are balanced by regulatory T cells (send signals to calm the body down)
* B cells (humoral immunity)
- A type of lymphocyte produced in the bone marrow (1-6% of blood)
- B cells differentiate into plasma cells and produce antibodies that can destroy the cell
T and B cell responses are specific and have the property of ‘memory’. When a naïve T or B cell encounters a new antigen, it becomes a memory cell.
How exercise induces physiology changes to cells of the immune system
-How can we measure immune function
- Self reported illness -> Upper respiratory tract infections – number and severity
- Cellular level ->
* Concentration of immune cells (T and B-cells, neutrophils)
* Activation/ suppression markers on a specific cell type
* Measure immune cell function (e.g. movement of immune cell towards bacteria or virus) - Release of molecules reflecting immune response ->
* Antibodies with anti-microbial properties (e.g. salivary IgA)
* Enzymes with a role in phagocytosis (e.g. lysozyme) - In vivo immunity ->
* Antibody responses to a vaccine (Flu, Hepatitis B)
* Wound healing and/or skin thickening to mild trauma
Describe how exercise evokes a marked immune response
- Moderate intensity exercise (~50% VO2 max – orange) increases the number of leukocytes in blood
- This increase is greater in the minutes after intense exercise (~80% VO2 max – green), followed by a drop below rest in the hours later
- This decrease is a result of dynamic and complex physiological response
Mechanisms driving immune cell mobilisation
-Mechanisms driving immune cell mobilisation -> Exercise increases shear stress, sympathetic drive/ vasoconstriction and adrenaline concentrations that demarginate immune cells into peripheral blood. This response is not uniform, with effector immune cells being preferentially mobilised (effector T cells and natural killer cells)
What are cells mobilised during exercise doing
-There is increased blood pressure and shear stress during exercise.
-Highly functional cells mobilise other cells during exercise
-The response during exercise from cells is not mobilised
Use the diagrams on the notes to explain hoe exercise regularly impacts on aspect of innate and adaptive immunity in the context of clinical health
Describe exploiting the acute immune response to exercise
-Exploiting the acute immune response to exercise > Bouts of exercise enrich the bloodstream with T cells, stem cells and natural killer cells. These inhibit tumour growth an fight off pathogens.
Describe the impact of exercise on immunity and relevance to metabolism
-Immunity and the immune system
-Immunity -> The immune system consists of organs, cells and chemical and is broadly defined into 2 branches:
* Innate (non-specific)
* Adaptive (specific)
The immune system primarily governs how the body defends against foreign pathogens including viruses (cold, flu), bacteria (pneumonia), and fungi (yeast). A fundamental principle of immunity is being able to recognise ‘self’ vs ‘non self’ and ‘altered self’. Bone marrow is a primary lymph organ which produces cells for the innate and adaptive branches.
The impact of exercise on immunity and relevance to metabolism
-Metabolism of immune cells + shifting metabolism in immune cells
-Metabolism of immune cells ->
* In a ‘resting’ T cells (i.e. naïve T cell), the primary metabolic pathway used to support cell membrane integrity and movement is mitochondrial respiration
* Upon activation (e.g. virus, bacteria), T cells rely heavily on glycolysis to rapidly provide the ATP they need to move (i.e. to the site of infection) and produce the molecules needed to destroy virus infected cells)
-Shifting metabolism in immune cells -> Theory suggests that the immune cell activation might become impaired after heavy exercise as the oxygen and nutrient demands od the cell exceed its metabolic capacity. Regeneration of NAD+ is a limiting factor. Immune cells need significant amounts of energy to respond effectively and initiate an appropriate immune response.
The impact of exercise on immunity and relevance to metabolism
-Moderate v Heavy training loads
- A central notion in exercise immunology research has been that moderate amounts of exercise enhance immune function
- Conversely, some researchers contest that arduous exercise bouts or periods of intensified training can impair immune function
- The above interpretations have come from both acute (single session) and chronic (period of intensified training) exercise studies.
