Immune System Flashcards
What is the immune system
Refers to the collection of cells, tissues and molecules that mediate reactions to pathogens and some non infectious substances (e.g. harmless environmental molecules, tumours and self molecules)
What is the immune response
The coordinated, tightly controlled response of these cells and molecules in the immune system
What is immunity
Often described ass resistance to infectious diseases
E.g. resistance to bacterial, viral, fungal, parasitic infections. However non infectious subatces, damaged and tumour cells can also elicit some immune responses
What are the functions of the immune system
Prevent infection
Eradicate established infections
Control tissue regeneration (wound healing)
Detect and eliminate tumours
Tolerate self (i.e. coexist with our own cells without causing damage)
What are congenital (primary) immune deficiencies
Patients who completely lack key cells and molecules of the immune system. This has severe outcomes
What are acquired (secondary) immune deficiencies
secondary immunodeficiencies (SIDs) are acquired declines of immune cell counts and or/function.
What happens when the immune system overreacts
Asthma
Atopic or allergic reactions
Autoimmune diseases such as sclerosis, SLE, type 1 diabetes
Where is the immune system
It is integrated with other systems such as GI, cardiovascular, respiratory, nervous, endorcine, skin etc
Immune cells are scatterd throughout the body, many of which actively travel (migrate) around it. Whereas others must sit in one place for a long period of time (tissue ‘resident” immune cells)
What is an autocrine function
Autocrine signaling is a form of signaling in which a cell secretes a hormone or a chemical substance that binds to the receptors on the same cell, leading to functional changes in the cell,
What is a paracrine function
paracrine signaling is a form of cell signaling in which the target cell is near the signal-releasing cell
What is an endocrine function
Signalling throughout the whole body
What is the anatomy of the immune system
Physical and chemical barriers
Cells and molecules of the immune system which access most organ systems in the blood: i.e. blood and lymphatic vessels
What are the physical and chemical barriers of the immune system
Epithelial cells of skin, gut, respiratory tract
Secretions including sweat, wax and tears
Mucus in the nose, trachea, gut
Urine
Proteolytic enzymes
Low stomach pH
Normal gut flora
Central and peripheral immune system/tolerance
What are hallmarks of the innate immune system
1) Speed - it is early and rapid - fast acting
2) Short lived duration
3) Repetitive - responds the same way each time a microbe is encountered
4) Interactive - with other cells of the innate and adaptive immune system
5) Non reactive to the host
What are the components of innate immunity
1) Epithelial barriers
2) Cells in circulation and tissues; phagocytes, exocytes
3) Molecules such as cytokines and blood proteins
What do phagocytes do
Their main role is to circulate and migrate through tissues to ingest and destroy both microbes and cellular debris.
What do exocytes do
Contains granules which has toxic enzymes to kill pathogens
What do cytokines do
These are small proteins produced and secreted by many different cell types
They modulate inflammatory and immune reaction
Key mediators of communication between cells
Can target cells in an autocrine/paracrine/endocrine manner
What do chemokines do
These are chemo-tactic cytokines
Different cells express different chemokine receptors allowing them to respond to different chemokines
It helps move cells from a low chemokine concentration to a chemokine concentration
What do blood proteins do
Plasma proteins, sometimes referred to as blood proteins, are proteins present in blood plasma. They serve many different functions, including transport of lipids, hormones, vitamins and minerals in activity and functioning of the immune system.
What is the function of the epithelial barrier
Form of physical protection
What is the role of inflammation in immune function
Inflammation is the immune system’s response to harmful stimuli, such as pathogens, damaged cells, toxic compounds, or irradiation [1], and acts by removing injurious stimuli and initiating the healing process [2]. Inflammation is therefore a defense mechanism that is vital to health [3].
It is able to do this by increasing blood flow to the area, thus allowing for greater white blood cells to reach the area and fight off infection or potential harm
Why is resolution of inflammation important
A little bit of inflammation (caused by cytokines) is okay and considered good. However, too much can be bad
For example, it could lead to septic shock, chronic inflammation (arthiritis, cancer, inflammatory bowel disease, diabetes). May even lead to death
Explain process of inflammation
1) Pathogens invade body tissue.
2) Stimulates mast cells to release histamines
3) Histamines trigger vasodilation and increased permeability in local blood vessels
4) Plasma proteins and fluid enter tissue
5) Complement and antibodies in plasma protein neutralise the pathogens
6) Pathogens and debris can also trigger macrophages to release cytokines and chemokines
7) Cytokines act on endothelium of local blood vessels to increase adhesion molecules for white blood cells
8) Neutrophils begin to bind onto adhesion molecules and roll along endothelial surfaces
9) Eventually stop and adhere onto endothelium
10) They change their shape, push through gaps between endothelial cells to reach underlying tissue (extravasation)
11) Once in tissue, they migrate down the chemokine gradient from low to high concentrations of chemokines at source of inflammation
12) The neutrophils phagocytose the foreign substance and cell debris while secreting inflammatory cytokines to further intensify the inflammation
What is central tolerance
Central tolerance mechanisms eliminate self-reactive lymphocytes during their initial development in the bone marrow and thymus. (Primary lymphoid organs)
What is peripheral tolerance
Peripheral tolerance mechanisms eliminate self-reactive lymphocytes that escape the radar of central mechanisms; in the peripheral tissues and secondary lymphoid organs. (I THINK)
What are the primary lymphoid organs
Bone marrow thymus
What are the secondary lymphoid organs
Spleen
Lymph nodes
Mucosal and cutaneous associated lymphoid tissues
What are dendritic cells
These are antigen presenting cells that capture, process and present antigens to lymphocytes to initiate and regulate the adaaptive immune response
Has a lot of different ‘branches’
What are the main cells which are part of the adaptive immune system
Lymphocytes and their products (i.e. antibodies)
What are effector cells
These go and kill pathogens
What are memory cells
These respond to pathogens faster the second time
What are the two main types of lymphocytes
B Cells
T Cells
What are B cells
These are produced from bone marrow, and produces the antibodies used to attack invading pathogens
What are T cells
These destroy harmful pathogens by sending signals that help control immune systems response to threats
T-cells protect you by destroying harmful pathogens and by sending signals that help control your immune system’s response to threats.
What are the two types of adaptive immunity
Humoral immunity
Cell mediated immunity
What is humoral immunity
In humoral immunity, B cells secrete antibodies which eliminate extracellular microbes
(These are largely B cells)
What is cell mediated immunity
Cell-mediated immunity (CMI) is an immune response that does not involve antibodies but rather involves the activation of macrophages and NK-cells, the production of antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.
Helps phagocytes to destroy ingested microbes and help kill infected cells (These are largely T cells)
What are antibodies
These are sticky proteins released by B cells into extracellular fluid.
There aare two components to its structure; variable and constant region
What is the variable region
It is the part which binds onto antigens
What is the constant region
Determines mechanism used to destroy the antigen. Doesn’t vary between different antibodies in the same class
What are 3 different types of antibodies
IgM, IgG, IgE
What is IgM
Produced first by B cells. Pentamer structure
What is IgG
Efficient antiviral and antibacterial defence. Can only be made with T cell help –> takes time
What is IgE
Defence against worms and parasites. Activates basophils which release chemicals to kill
What are the two types of T cells
Helper T cells
Cytotoxic T lymphocytes
What is the function of helper T cells(Th)
“Help” other cells with the immune response
Different types of Th cells exist within specialised functions. Some helper T cells suppress or regulate immune response rather than activate immune response
Helper T-cells are a type of immune cell. When they sense an infection, they activate other immune cells to fight it. They may activate cytotoxic T-cells or they may activate B-cells, which produce antibodies.
What is the function of cytotoxic T lymphocytes (CTLs)?
CTLs kill their targets in a highly specific way. They may require help from helper T cells. And they play a key role in viral infections and anti tumour immunity
What is immunological tolerance
A system for determining which lymphocyte clones will be allowed to survive, based on whether they respond to body cells
Involves both central and peripheral tolerance
What is central tolerance
Central tolerance mechanisms eliminate self-reactive lymphocytes during their initial development in the bone marrow and thymus. (Primary lymphoid organs)
What is peripheral tolerance
Peripheral tolerance mechanisms eliminate self-reactive lymphocytes that escape the radar of central mechanisms; in the peripheral tissues and secondary lymphoid organs. (I THINK)
What are the two different factors which can influence autoimmune disease
Genetic and environmental factors
What are the genetic factors influencing autoimmune disease
Could be linked to the genes responsible for:
T cell activation
Maintaining immunological tolerance (finding and destroying self reactive lymphocytes and activity of regulatory cells)
What are the environmental factors influencing autoimmune disease
More common in women
Local trauma –> increased inflammatory reaction could reveal previously hidden antigens –> immunological reaction
Lack of exposure to various microbes when young
What is immune surveillance
The capacity to detect and destroy cancer cells
What are some new cancer therapies that target immune system
Bone marrow transplants (allows for treatment of certain types of leukeamia)
Re-engineered t cells (Chimeric antigen receptor (CAR) T cells for cancer)
Antibodies (remove immunological brakes and apply immunological acceleration by removing checkpoing inhibition immunologu. Cancer has the ability to hijack the T cells by engaging the brakes. The inhibitor prevents these breaks, allowing them to run rampage)
Impacts of immunity on cancer
Patients with tumours that have been infiltrated by lymphocytes have a better prognosis. Enlarged tumour draining lymph nodes = better prognosis. Transplanted tumours are rejected. Immunodeficient parties have increased susceptibility to tumour growth. (Transplant patients on immunoseppressive therapy and people with acquired immunodeficiencies)
What is part of the central immune system
Primary and secondary lymphoid organs
What is part of the peripheral immune system
Evereywhere else not the primary and secondary lymphoid organs
