immune system Flashcards
what does the immune system consist of?
- organs, cells and chemicals
what are the two categories of the immune system?
- innate
- adaptive
what is the innate branch of the immune system?
- non - specific response
- first to respond
what is the adaptive branch of the immune system?
- specific response
- involves T cells and B cells
what is the primary role of the immune system?
- governs how the body defends against foreign pathogens
- includes viruses (cold, flu), bacteria (pneumonia) and fungi (yeast)
what should the immune system be able to recognise?
- recognise ‘self’ vs ‘non self’ or ‘altered self’
where are most cells produced? what is this site known as?
- most cells produced in bone marrow
- known as primary lymph organ
what gland produces more mature cells?
- thymus gland
- cells navigate this after they are produced
what are secondary lymph organs?
- sites where the body detects infection
where are lymph regions?
- in lungs, intestines
what are physical barriers?
- a branch of innate immune system that
‘physically’ prevent a foreign substance from reaching the site of infection
what can microbes be? (3)
- trapped by skin cells or mucus
- killed by antibodies in tears, saliva+ mucus
- removed from body by shedding skin, coughing, vomiting, flushing bodily fluids (urine/ tears)
what are immune cells collectively named? do the two systems work together?
- collectively called white blood cells or leukocytes
- two systems work together as innate system sends specific signals to activate the adaptive system
what are the three main cells involved in cell- mediated response?
- monocytes
- neutrophils
- natural killer cells
what are monocytes? how much makes up the blood?
- type of phagocyte for microbes and dead cells
- 3 to 9% of the blood
what happens when monocytes leave the blood? what is formed?
- when they leave the blood they form macrophages in tissues
what are neutrophils? how much is in the blood?
- rapid responder to infection/ stress that exits the blood to enter tissues
- also known as a phagocyte
- 60% of the blood
what do neutrophils do?
- engulf microbes (phagocytosis)
- kill via release of toxic molecules (respiratory burst)
what are natural killer cells? what percent is found in the blood?
- destroy virus - infected and cancer cells
- 1 to 6%
what do natural killer cells produce?
- proteins such as cytokines to kill infected/ cancerous cells
what do innate immune cells recognise?
- pathogen associated molecular patterns (PAMPs)
what does humoral response involve?
- complement proteins
- made in liver and bind to antibodies or PAMPs on microbes (bacteria) or dead cells
what do complement proteins form? what does this recruit and how?
- form complexes
- recruit phagocytes to the site via chemical gradients; complement cascade
what other proteins can be released from innate immune cells? what do they do?
- cytokines
- kill infected cells or signal to adaptive immune system
what cell bridges innate and adaptive immunity? what do they present?
- dendritic cells
- process parts of a foreign body and present antigen to cells of adaptive immune system in lymph nodes
- known as antigen presenting cell
what are the adaptive immunity cells involved in cell mediated immunity? where are they developed and what is the percent?
- T cells
- cells themselves kill disease
- developed in thymus
- 20 to 40%
what do T cells release?
- cytokines that kill virus infected cells or tumours
what is the cell- mediated response balanced by?
- regulatory T cells
- send signals to stop
what adaptive immune cells are used in humoral response? where is it produced and what percent?
- B cells
- non- cellular process
- produced in bone marrow
- 1 to 6% of the blood
what do B cells differentiate to? what do these cells produce?
- differentiate into plasma cells
- produces antibodies that can destroy cells
what properties do T and B cell responses have?
- specific
- property of memory
what happens when a naïve T or B cell encounters a new antigen?
- it becomes a memory cell
- pool of memory cells for future infections
how do T cells work?
- killer T cells strongly adhere to cancer cells
- T cells releases pore forming toxins and cytokines that results in cell death
how do B cells work?
- differentiate into plasma cells, which release Y shaped antibodies
- antibodies work to recognise molecular shape on infected cells
- form a complex to recruit phagocytes to destroy the cell
how can you preserve immunity?
- through exercising
what are the four ways that immune function can be measured?
- self- reported illness
- cellular level
- release of molecules reflecting immune response
- in vivo immunity
describe self- reported illness as a means of measuring immune function
- upper respiratory tract infections
- number and severity
describe cellular work as a means of measuring immune function
- 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
describe release of molecules reflecting immune response as a means of measuring immune function
- antibodies with anti- microbial properties e.g., salivary IgA
- enzymes with a role in phagocytosis e.g., lysozyme
describe in vivo immunity as a means of measuring immune function
- antibody responses to a vaccine (flu, hepatitis B)
- wound healing and/ or skin thickening to mild trauma
what happens to naïve cells as you get older?
- number of naïve cells decline
- slower immune response
what does moderate exercise at 50% V02 max increase?
- number of leukocytes in blood increases
when is increase greater in intense exercise at around 80% V02 max?
- increase greater in minutes after
what happens to leukocytes number in the hours following exercise (recovery stage) ?
- drop below rest in hours later
- result of dynamic and complex physiological responses
what is the ‘ open window for infection’ hypothesis ?
- gap in recovery; lower numbers of leukocytes means the body is less able to fight off infections
what mechanism drive immune cell mobilisation into the peripheral blood?
- exercise increases shear stress, sympathetic drive/ vasoconstriction and adrenaline concentrations that demarginates immune cells to blood
what is the response of exercise mechanism driving immune cell mobilisation described as and why?
- not uniform
- effector immune cells (effector T cells and natural killer cells) prefentially mobilised
- increased cytokines responsible for highly functionable cells
what happens to highly functionable immune cells like effector T cells and natural killer cells after exercise?
- migrate to sites where the body may encounter damage or infections e.g., muscle, lungs, guts, bone marrow
- t cells in blood decreases in blood after strenuous exercise
what does data indicate about the cells that are most sensitive to mobilisation during exercise?
- those most sensitive (effector natural killer cells and T cells) alter their function during the bout of exercise
describe the 5 ways cells are mobilised during exercise
- shift metabolism to glycolysis
- increase cytotoxicity
- anti- tumour activity
- antigen binding
- tissue migration
how do metabolic pathways apply to immune cells?
- in a resting T cell (naïve) , the primary 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 to site of infection, and produce the molecules needed to destroy virus infected cells
what does theory suggest about immune system after heavy exercise?
- suggests that immune cell activation may become impaired as the oxygen and nutrient demands of the cell exceed its metabolic capacity
what do immune cells require?
- significant amount of energy to respond effectively and initiate an appropriate immune response
describe interpretations of moderate vs heavy training loads- where do these come from?
- moderate amount said to enhance immune function
- some concluded that arduous exercise bouts of intensified training can impair immune function
- come from acute (single session) and chronic (period of intensified training) exercise studies
what are the benefits of moderate exercise?
- more antibodies
- more immune cells
- reduced inflammation
- better function of immune cells
- better vaccine response
what are the implications of heavy exercise on the immune system?
- less antibodies
- less responsive immune cells
- reduced number of immune cells
- reduced function
- poorer redistribution
what are the 7 ways that exercising training promotes maintenance of immune homeostasis ?
- reduced number/ severity of infections
- increased antibody response to vaccination
- increased wound healing
- increased surveillance of cancer cells
- reduced pro- inflammatory environment surrounding excess adipose tissue
- reduced chronic systemic inflammation associated with cardiovascular, metabolic and neurological illnesses
- increased vasculature health and thus immune cell recirculation
how is immunity in older age maintained by exercise? (four ways)
- preserves naïve B cells
- preserves naïve CD4+ T cells
- preserves naïve CD8+ T cells
- promotes a favourable cytokine profile that protects the ageing thymus
how does physical activity reduce cardiometabolic disease?
- reduces plaque size and macrophage content
- lowers number of inflammatory cells
- improved thymus health; naïve T cells, regulatory T cells, inflammatory T cells
- reduced adipose tissue T cell content
