bio 7.2.1 Vertebrate immune system

FINISHED

Pathogens definition

agents that cause disease, infect a wide range of animals, including humans

Which animals have innate immunity

All animals

Which animals have adaptive immunity

vertebrates

1st line of defense in body

skin, mucous membranes and their secretions

2nd line of defense in body (3)

antimicrobial substances, inflammation and fever, phagocytic white blood cells

3rd line of defense

Specialized lymphocytes (B cells and T cells)

which type of immunity is present before any exposure to pathogens and is effective from the time of birth?

Innate

What does innate immunity consist of? (2)

external barriers, internal cellular and chemical defenses

What immunity develops after exposure to agents such as microbes, toxins, or other foreign substances

Adaptive

In innate immunity what does recognition and response rely on?

Traits common to groups of pathogens

Is innate immunity present in vertebrates?

Yes

What do barrier defenses include? (what, of what tracts?)

Skin and mucous membranes of the respiratory, urinary and reproductive tracts

Examples of body fluids which are hostile to many microbes?

Saliva, mucous, tears

What feature of the pH of skin and the digestive system prevents growth of many bacteria?

It is low

TLRs definition

Toll-like receptors

What do cellular innate defences include? (4)

Phagocytic cells, (in verebrates) Natural Killer cells, Lymphatic system

How do phagocytic cells recognize groups of pathogens

By TLRs

4 types of Phagocytic cells

Neutrophils, Macrophages, Dendritic cells, Eosinophils

neutrophils description (where they are found, how they are activated, what they do)

Circulate in blood and are affected by signals from infected tissues, engulf and destroy pathogens

macrophages description (where they are found, alternative name)

Found throughout the body (especially lymphatic system and spleen), also called “big eaters”

Dendritic cells description (where they are found, what they do)

Found in the skin, stimulate the development of adaptive immunity

Eosinophils description (where they are found, what they do, who do they target)

Found beneath mucosal surfaces, discharge destructive enzymes against multicellular invaders (e.g. parasitic worms)

Natural Killer cells description (where they are found, what they do, who do they target?)

Circulate throughout the body and detect abnormal cells, release chemicals leading the cell death, inhibiting the spread of virally infected or cancerous cells

What does the lymphatic system consist of? What are their functions? (2)

Lymphatic vessels through which lymph (fluid in the lymphatic system) travels, structures (nodes and organs) that trap foreign substances

Lymphoid organs (6)

Spleen, thymus, appendix, Peyler’s patches, adenoid, tonsils

Examples of peptides and proteins of the innate immune system (2)

Interferon and proteins of the immune system

How do peptides and proteins function in the innate immune system? (2)

By attacking pathogens or impeding their reproduction

Interferon- what is it, what types of organisms is it found in, function?

protein unique to vertebrates, induces nearby uninfected cells to produce substances that inhibit viral reproduction

What is interferon produced by?

Virus-infected body cells

How many proteins make up the complement system?

About 30

Where can you find proteins of the complement system and in what state?

They circulate in the blood plasma in an inactive state

Who are the proteins of the complement system activated by and what do they do?

Activated by microbes, causes lysis of invading cells and helps trigger inflammation

What is a mast cell?

A type of cell of the connective tissue which releases histamine

What does histamine do?

triggers blood vessels to dilate and become more permeable

Local inflammatory response- what is it brought about by, what does it include (5 signs)? (general)

brought about by molecules released upon injury of infection, includes redness, swelling, heat, pain and loss of function

Cytokines in the inflammatory response- what are they released by, what are its effects, what do the effects cause?

Released by activated macrophages and neutrophils, it signals molecules that promote blood flow to the site of injury, causing redness and increase of skin temperature

Examples of what can trigger acute inflammation (2)

cell or tissue damage, presence of dead cells or noxious agents such as bacteria

What is the first phase of wound healing?

Acute inflammation

What does the acute immune response aim to do?

remove the injury causing agent and limiting the extent of tissue damage

Acute inflammatory response step 1 (2 things)

Mast cells release histamines, macrophages release cytokines that cause capillaries to dilate

Acute inflammatory response step 2 (2 things)

Capillaries are now more permeable and allow fluid containing antimicrobial peptides to enter the tissue, neutrophils are attracted.

Acute inflammatory response step 3 (1)

Neutrophils digest pathogens and cell debris

Pus definition

A fluid rich in white blood cells, dead pathogens, and cell debris from damaged tissues

Septic shock definition

A life-threatening condition caused by an overwhelming inflammatory response

Fever- what is it, what is it triggered by

Systemic inflammatory response triggered by pyrogens (e.g. interleukin 1)

What releases pyrogens

Macrophages and toxins from pathogens

Fever phase 1

Pathogen or toxin- most common cause is infection from bacteria/viruses, macrophage ingesting that will start the process

Fever phase 2 (4 ish sub-steps)

Macrophages respond- by ingesting, they destroy the pathogen, releasing endotoxins, which induce the production and release of interleukin-1 into the bloodstream

Fever phase 3- interleukin 1

Interleukin-1 travels to the brain, induces the hypothalamus to produce more prostaglandins which resets the bodys “thermostat” to a higher temperature, producing fever

Hypothalamus function

Controls the bodys temperature settings

Prostaglandins function

Resetting the bodys thermostat to a higher temperature, producing fever

Fever phase 4 (+ 3 results) (after interleukin 1 in brain)

Fever onset- body raises temperature resulting in: blood vessel constriction, increased metabolic rate, shivering

Fever phase 5 (after fever onset)

Chill phase- skin remains cold, shivering occurs, this stops once the body reaches the setting of the thermostat

Fever phase 6 (final phase)

Crisis phase- increased body temperature remains until the interleukin-1 is eliminated, heat reducing methods (sweating, vasolidation (widening of blood vessels)) cause the person to feel warm, it indicates the bodys temperature falling`

Examples of how some pathogens avoid destruction

Modifying their surface to prevent recognition, resisting breakdown following phagocytosis

Two types of aquired immunity

Naturally aquired, artificially aquired

Two types of naturally aquired immunity (+ brief explanations)

Active (getting the disease, even when no symptoms), passive (from mother to fetus through placenta or milk)

Two types of artificially aquired immunity (+ brief explanations)

Active (vaccines), passive (immune serum, eg antivenom, no antibodies produced)

Lymphocytes that mature in the thymus

T-cells

Lymphocytes that mature in the bone marrow

B-cells

Two types of lymphocytes

B-cells and T-cells

Antigen definition (in relation to B cells and T cells)

A substance that can elicit a response from a B or T cell

Epitope definition

The small, accessible part of an antigen that binds to an antigen receptor

A feature unique to the adaptive immune system with lymphocytes

Each individual lymphocyte is specialized to recognize a specific type of molecule

How can B or T cells bind to foreign molecules?

With receptor proteins

B cell antigen receptor structure

A Y-shaped molecule with two identical heavy chains and two identical light chains, connected by disulphide bridges, heavy chains go through plasma membrane into cytoplasm- has a transmembrane region

What varies in B-cell antigen structure?

The variable regions, at the tips of the light and heavy chains

What do the variable regions in B-cells provide

Antigen specificity

What is the difference between antibodies and B cell receptors?

Antibodies lack transmembrane regions that anchor receptors in the plasma membrane

What does the binding of a B cell antigen receptor to an antigen give rise to?

Cells that secrete a soluble form of the protein called an antibody or immunoglobin (Ig)

T-cell receptor structure

Two different polypeptide chains (alpha and beta)

What do T-cells bind to?

Antigen fragments presented on a host cell

MHC definition

Major histocompatibility complex, are host proteins that display the antigen fragments on the cell surface

Antigen presentation description

In infected cells, MHC molecules bind and transport antigen fragments to the cell surface

What can a T cell bind to?

Both the antigen fragment that is displayed and the MHC molecule

What interaction is necessary for the T cell to participate in the adaptive immune response?

T cell binding to the antigen fragment displayed and the MHC molecule

How are lymphocytes activated once an antigen is found?

In the lymph nodes, the antigen is exposed to a steady stream of lymphocytes until a match is made, the binding initates the activation

Clonal selection definition

Proliferation of lymphocytes, the cell divisions that B and T cells undergo

Two types of clones produced during clonal selection & brief descriptions?

Effector cells (short lived, act immediately against an antigen) and memory cells (long lived, can give rise to effector cells if the same antigen is encountered again)

Effector cells in B cells name

Plasma cells

What is immunological memory responsible for?

Long-term protection against diseases due to either a prior infection or vaccination

What is the first exposure to a specific antigen called? + Brief description

Primary immune response, selected B and T cells give rise to their effector forms

What is special about the secondary immune response?

Memory cells facilitate a faster, more efficient response

ELISA test description

A type of analytic biochemistry assay that uses a solid phase enzyme to detect the presence of an antigen, in a wet sample

ELISA example procedure steps (3)

Virus sample on surface, antibody with enzyme conjugate attached to viral antigen, substrate and enzyme interaction create color change for detection

Two branches of aquired immunity

Humoral and cell-mediated

Humoral immune response simple explanation

Antibodies help neutralize or eliminate toxins and pathogens in the blood and lymph

Cell-mediated immune response simple explanation

Specialized T cells destroy affected host cells

Look at and explain this graph and then type done

Done

Cell-mediated immune response part description of diagram (from 1st exposure to antigen) (maybe draw on paper if available to make it easier?)

Antigen 1st exposure - engulfed by antigen presenting cell - stimulates BOTH cytotoxic T cell and helper T cell - Cytotoxic T-cell gives rise to - BOTH memory T cells and active cytotoxic T cells - Helper T cells give rise to memory helper T cells which stimulate - memory cytotoxic T cells

Antigen 2nd exposure - stimulates memory helper T cells AND memory cytotoxic T cells

Humoral (antibody-mediated) immune response part description of diagram (maybe draw on paper if available to make it easier?)

Antigen 1st exposure - that AND Helper T cell - stimulates B cell which gives rise to - Plasma cells and Memory B cells - Plasma cells secrete antibodies - Memory B cells also give rise to Plasma cells

Antigen 2nd exposure - stimulates memory B cells together with Memory helper T cells

Helper T cells function

Signals from them: initiate production of antibodies that neutralize pathogens AND activate T cells that kill infected cells

What types of cells have class I and II MHC molecules on their surface

Antigen-presenting cells

What molecules are the basis upon which antigen-presenting cells are recognized?

Class II MHC molecules

What happens when a helper T cell binds to an antigen and the class II MHC molecule? (three main ideas)

Signals are exchanged then the helper T cell is activated, proliferates, forms a clone of helper T cells which then activate the appropriate B cells

Effector cell in cell mediated immune response name

Cytotoxic T cell

Cytotoxic T cell function

Recognizes fragments of foreign proteins on infected cells, possess an accessory protein that binds to class I MHC molecules, then activated cytotoxic T cell secretes proteins that disrupt cell membranes of target cells and trigger apoptosis

Apoptosis definition

Programmed cell death

What is the humoral immune response characterized by?

The secretion of antibodies by B cells

Activation of B cells description

In response to cytokines from BOTH helper T cells and an antigen, a B cell proliferates and differentiates into memory B cells and antibody-secreting effector cells (plasma cells)