IMMUNITY Flashcards
What are antigens
Antigens are molecules, or part of a molecule that elicit an immune response
Difference between self and non self antigens
A molecule on an organism’s cells that the immune system recognizes as healthy self cell, preventing an immune response.——self antigen is a type ofmhc marker epexressed on humansand other verterbrates
whereas,
A molecule from outside the body that is recognized by the immune system and initiates an immune response.
compAREMHC class I and MHC II markers
MHC class I
Found on all nucleated cells in the body
Not found on RBC due to lack of nucleus
MHC class II
on specialised antigen-presenting cells; interact with T helper cells during antigen presentation by presenting antigen presenting cells on T helper cells to help initiate an immune response against pathogens.
since Red blood cells do not contain MHC markers, what do they use to mark themselfs as ‘self’
Red blood cells contain glycoproteins to label them ‘self’
rbs have no nucleus so no mhc marker
autoimmune disease
Failure to recognise self from non-self leads immune system atttack self cells resylts jjn to an autoimmune disease. Examples include multiple sclerosis, Type 1 Diabetes, rheumatoid arthritis.
allergic reaction
Over reaction to an otherwise harmless non-self antigen is known as an allergic reaction. Common allergens are eggs, seafood, peanuts.
what are pathogens and what are the 2 cateorgie sof pathogens and provide examples of these
Pathogens are foreign agents that cause disease
Can be either
Cellular: have a cellular structure and are living. Examples include bacteria, parasites, fungi.
Non-cellular: do not have a cellular structure and are typically non- living. Examples include viruses, prions.
Bacteria, what type of path9ven are they, how do they cause cellular death, some are good bc, how are they fought/treated
Cellular pathogens
Unicellular prokaryotes reproduce via binary fission
Releases toxins and enzymes causing cells to lyse death
Some are beneficial in the GI tract.
Treated with antibiotics
Fungi
Cellular pathogen
Eukaryotic cells reproduce via spore formation (sexual or asexual reproduction)
Contain cell wall but no chloroplasts
Include yeast and moulds
Thrive in moist conditions
Protozoa
Cellular pathogen
Single celled eukaryotes
Requires a host to feed on and reproduce
Viruses
Non-cellular pathogens Invade cells and replicate using host cells.
Made up of genetic material (DNA or RNA) inside a protein coat (capsid)
Requires a host cell to replicate
Antigens can mutate making it difficult for our immune system to respond quickly.
Prions
Non-cellular pathogen
Made up of protein only (no genetic material)
Causes other proteins to misfold
Can infect the brains of some mammals (e.g. mad cow disease)
Types of barriers
Physical: Barriers that block or hinder pathogens from entering
Chemical: Barriers that work by producing chemical substances to inhibit the growth/ destroy pathogens
Microbiological: non-pathogenic bacteria (normal flora) to prevent growth of other bacteria competes with bad bacteria addxsmth a good a good uis
Barriers in plants
Physical – including thick bark to prevent entry of pathogens, waxy cuticles on leaves, thorns, stomata closing.
Chemical – include tannins from tea which a toxic to insects, phenols to repel microorganisms, caffeine which is toxic to insects and fungi, other enzymes that disrupt cell membranes of fungi.
Barriers in animals (physical)
Physical barriers include
Intact skin
Mucous secretions
Hairs in the respiratory tract
Cilia
Mucous Secretions and Cilia: Sweep pathogens away from airways and into the throat to be destroyed by the gastrointestinal tract.
Intact Skin: Forms a continuous layer that prevents pathogen entry.
Body Hair: Prevents foreign particles from directly contacting the skin.
Barriers in animals (chemical
Chemical barriers include
Lysozyme enzymes in tears and saliva to destroy bacteria
Acidic sweat
Earwax containing antibacterial compounds
Antibacterial proteins in semen
low pH in vagina
Stomach acid
Sweat: Lowers the pH of the body, contains toxic lipids, and washes microbes away.
hydrchlori acid: Break down complex carbohydrates, destroying potential pathogens.
Ear Wax: Hydrophobic nature, acidic pH, and antimicrobial properties protect the ear canal from infections.
Barriers in animals (microbiological)
Microbiological barriers include
Bacteria on the skin
Bacteria in the GI tract
Bacteria in the vagina
All prevent the grown or colonisation of pathogenic microorganisms as they compete for space
compare the first, second and third line of defence.
pathogen
A foreign substance that causes a disease.
wjat are MHC makrers
MHC markers are proteins found on the surface of self-cells that allow the immune system to differentiate between self-cells and non-self cells.
What are phagocytes and types of phagocyte sand explain
Specialised leukocytes responsible for endocytosis and the destruction of pathogens, foreign material, and cell debris
types of pahgocytes
process of phagocytutpsisi
When a pathogen is recognised as non-self, it is engulfed by a phagocyte via endocytosis
The pathogen is enclosed in a vesicle inside the cell and fuses with a lysosome. Enzymes in the lysosome digest the bacteria
Fragments are released as waste via exocytosis OR if the phagocyte is an antigen presenting cell, fragments are displayed on the MHC class II marker to present to the adaptive immune system
what are the antigen presetnign cells
Antigen-presenting cells (APCs) are specialized immune cells that capture, process, and present antigens on MHC (Major Histocompatibility Complex) molecules on their surface to T helper cells, activates T helper cells, helping to initiate the adaptive immune response
what are macrophagres, denndeirtc cells and neutrophils
macropahges apc Engulfs pathogens thendisplays antigen of thepathogen on MHC IImarker
dendritic cells to t helper cell
Dendritic cells mosteffect APC specialized antigen-presenting cells that capture and process antigens to activate T cells, serving as a crucial link between the innate and adaptive immune systems.
responsible for the initiation of adaptive immune responses
neutrophils s: Neutrophils are the most abundant type of white blood cells that rapidly respond to infection by phagocytosing bacteria and releasing enzymes to kill pathogens.
the role of natural killer cells eosinophils and mast cellsin the innate immune system
Natural killer cells are Large granulated cells which target both abnormal cells such as cancer cells and virus infected cells by release cytotoxic chemicals to virus infected cells causing apoptosis
Eosinophils are large granulated cells containing toxic chemicals which help destroy pathogens that are too large to be engulfed via phagoctyosis.
Mast cells detect injury and are responisbel for releasing histamine during allergic and inflammatory responses.
Two receptors on NK cells:
and explain what they are and how thye owkr
Two receptors on NK cells:
Killer inhibitory receptors: examine MHCI markers (1)
Killer activation receptor: binds to molecules on infected cells (3)
NK examines cells for MHCI markers. If present, killer inhibitory receptor binds with MHCI and no cell death.
If the NK cell examines the infected cell and does not bind to MHCI markers, then the killer activation receptor is activated leading to cell death.
what does inflammation do and what does excessive histamine lead to
Inflammation increases blood flow to the site of infection, causes swelling and redness
Excessive release of histamine can lead to allergic reactions
what are cytokines, why are they released by the immune system and the respones of cytokines/what it causes
Group of signalling molecules made up of proteins which aids in communication between immune cells and helps protect against pathogens
Released by immune cells to help guide other immune cells to the site of infection
Responses include:
Induce inflammation
Induce fever
Attract macrophages
Promote proliferation of lymphocytes (third line of defence)
Interferons and compelemt proteins what are they
A type of cytokine released by virally infected cells to increase the viral resistance of neighbouring uninfected cells.
complement proteins are a group of proteins that assist immune cells by causing opsonisation, chemotaxis and lysis, which involves forming the membrane attack complex (MAC) that leads to the destruction of pathogens and
What are the actions of complement proteins/ what do complement proteins do when their activated.
Opsonisation: complement proteins stick to pathogens to allow phagocyte to recognise them as foreign. (figure 8)
Chemotaxis: attract more phagocytes to the site of infection (figure 9)
Lysis: form a membrane attack complex (MAC) resulting in lysis (cell bursts and destroyed) (figure 10)
what is antigen presentation
Macrophage/dendritic cells engulf pathogen and displays foreign antigen on MHC class II marker to T helper cell and it is required to intitate the adpative immune systme
mechanisms of antigen presentation
what is a fever, what happens to pathogen in elevated temperatures, how do fever help the immune systme
Rise in temperature in response to an infection.
Pathogens are unable to survive elevated temperatures
Fevers help the immune system by activating certain proteins in the body that bolster defences
However, prolonged fevers can have a negative effect on the body as cells are no longer functioning at their optimal temperature.
what is inflammation the resutl of, what does inflammation do chracteristicis/sytmptoms of inflammation and what does it inovvle(steps)
Inflammation is a result of increased blood flow to an injured area
Brings many immune cells and chemicals to the site of infection
Characteristics of inflammation: pain, redness, heat, swelling at the site of infection
Process involves initiation, vasodilation and migration
Steps of inflammatiojn
Initiation:
Pathogen enters the body through an open cut or wound
Platelets surround the area to prevent further entry of pathogens
Injured cells release cytokines to attract neutrophils to engulf pathogens
Vasodilation:
Mast cells release histamine to cause vasodilation in neighbouring vessels. This causes blood vessels to widen, increasing blood flow to the injured site.
This also increases permeability of immune cells from the blood vessels to damaged tissue.
Migration:Vasodilation allows phagocytes such as macrophages and neutrophils to the injured site.
Results in phagocytosis of pathogens
Complement proteins are attracted to pathogens to assist phagocytosis.
Pus forms (dead immune cells and pathogens)
Response continues until the site is cleared of pathogens
Features of the adaptive immune systme
Specificity: response is unique to the pathogen
Immunological memory: adaptive immune system stores a memory of previously encountered pathogens to allow for a fast response in subsequent exposures.
T helper cells become ‘selected’ to help initiate either
Humoral response or
Cell-mediated immune response
What are antibodies
Antibodies are proteins that travel in the blood to enhance phagocytosis (does not kill pathogens)
If the natural killer cell binds to both natural killer inhibitor and killer activator receptor, then
If the natural killer cell binds to both natural killer inhibitor and killer activator receptor, then nothing happens pathogen survives because there insufficient binding of the killer activator recprotr for the MHC class I markers.
differnce between the innate and adaptive immune system
the innate immune system is non specific, does not have immunological memory and the response is immedidate or occurs with hours of an infection but occurs for a short period of time
Whereas, the adaptive immune system is specific, invovles B and T lymphocytes, response takes longer to develop typically days or weeks after a expsoure to pathogen, it stores immunological memory allwoing for faster responses upon subsequenet epxosreus to the pathogen
Humoral immunity what is it, where do B lymphocytes come from and the 2 types of B cells.
Originate in the bone marrow and complete their maturation in the lymphoid organs and tissues
Two types of B cells:
Plasma B cell – once activated, produce 1000’s of antibodies to one type of antigen. Are short lived
Memory B cells – remain in the lymphoid tissues for long periods and produce 1000s of antibodies if the same pathogen is encountered
Initiation of the humoral immune system steps
**Step 1: Selection of B cell
A pathogen with an antigen that is complementary in shape to the antigen-binding site on the receptor of a naïve B cell interacts with that B cell. When this occurs, the B cell is said to have been ‘selected’.
Step 2: Selection of Helper T cell
Once a B cell has been selected, a helper T cell with a complementary receptor to the antigen is selected.
Cytokines are released to cause clonal expansion (many copies of the B cell)
Step 3: Clonal expansion and differentiation
Differentiation of B cells into memory B and plasma cells.
Memory B cells provide immunological memory
Plasma cells produce antibodies
Step 4: production of antibodies
Antibodies are secreted into the blood to defend against the selected pathogen
ANTIBOIDES have specific binding sites to the antigen’s binding site.
What are antibodies alos known as, what structure are they,, describe the structreu
Also known as immunoglobulins (Ig)
Antibodies contain four polypeptide chains including two heavy and two light chains (thus quaternary structure).
Two heavy chains are joined by a disulphide bond.
Contains a constant region (stem) and a variable region which form antigen bind sites.
Two binding sites are specific to the same antigen allowing them to bind to multiple pathogens
Action of antibodies
Neutralisation: Antibodies can block the sites of pathogens that can attack a host cell
Neutralisation: Antibodies can block the sites of pathogens that can attack a host cell
Neutralisation: Antibodies can block the sites of pathogens that can attack a host cell
Opsonisation: antibodies can bind directly to the surface of pathogens making them easier to phagocytose
Activation of complement proteins: Antibodies attach to pathogens to facilitate the actions of complement proteins. MACs (membrane attack complexes) form causing cell to lyse
what is clonla expansion and diffieirnation
refer to atar notes book
How allergic reactions occur
Sensitiation:
1. Exposure to antigen
2. Recogniton of allergen as a pathogen and B cell is selected and diffireenatesto produce ANTIBOIDES
- Plasmia B cells produces many IgE antibodies
- IgE antibodies bind to mast cells(via the constant region)
Rexposure: - Rexposure to the same allergen
- Allergen binds to IgE antibodies on mast cells knwon as cross linking. This causes mast cells to degrnaulateand release histamine
- Histamine cuases vasodilation, constriction of airways, increased permabitly of blood vessels
- Anaphlaysis symptoms like difficulty breathing, redness of skin, swelling of mouth or vomiting
2 strategies a person could use to decreasechance of thunderstomr asthma and is it possible to devleop a vaccine against thunderstomr asthma
- People can reduce their risk of developing thunderstorm asthma by managing allergies and asthma with prescribed medications, such as antihistamines or asthma inhalers.
Staying indoors with windows closed during thunderstorms, especially when pollen levels are high, helps minimize exposure to allergens that trigger asthma
2.No, it is not currently possible to develop a vaccine specifically for thunderstorm asthma. Thunderstorm asthma is triggered by environmental factors, such as high pollen levels during thunderstorms, rather than a specific pathogen, so managing the underlying allergic reactions and asthma through medication and prevention is the key approach.
What is cell medidiated immunity, where do T lymphocytyes orignate from and types of t lymphcoytes
Cell-mediated immunity is the immune response that involves T cells directly attacking and destroying infected or abnormal cells, rather than relying on antibodies.
T lmyphocytes orginate frm stem cells and mature in the thymus gland
types:
HELPER T CELL-releases cytokines to stimualte Bcells to make antibioides and T cells to become active
CYTOTOXIC T CELL-
Receptors complement the antigen presented on APCs.
Once activated, can kill foreign, infected or abnormal host cells by releasing toxic chemicals
Chemicals such as perforins and granzymes cause the infected cell to lyse
MEMORY T cell
Produced during an infection and are stored for a faster and stronger response in subsequent exposure
role of helper t cells, cytoxitic t cells and memory t cells
HELPER T CELL-releases cytokines to stimualte Bcells to make antibioides and T cells to become active
CYTOTOXIC T CELL-
Receptors complement the antigen presented on APCs.
Once activated, can kill foreign, infected or abnormal host cells by releasing toxic chemicals
Chemicals such as perforins and granzymes cause the infected cell to lyse
MEMORY T cell
Produced during an infection and are stored for a faster and stronger response in subsequent exposure
Cell medidaited immune repsonse-
Step 1:
Antigen presentation on macrophage/dendritic cell to a naïve T cell with a T cell receptor that complements the antigen being presented
Step 2:
The naïve T cell is said to be ‘selected’ and stimulated by cytokines released by T helper cell to undergo clonal expansion and differentiation into cytotoxic T cells and memory T cells
Cytotoxic T cells leave the lymph node to the site of infection to kill infected cells (virus infected cell, cancer cells)
Memory T cells provide immunological memory
Step 3:
Cytotoxic T cells arrive at the site of infection.
They have specific T cell receptors to the antigen of the infected cell.
If a complementary antigen is located, it binds to the cells MHC I marker and will release perforins and granzymes to induce apoptosis
regulatory T cells,
slown down/suppress immune response
WHAT ARe memory B and T cells and why do they both remian in the blood for an extneneded period of time
B memory cells rapidly divide and form many plasma B cells when they encounter an antigen that matches their receptor.
T memory cells proliferate rapidly into T helper cells and cytotoxic T cells upon stimulation by an antigen-presenting cells that is presenting a previously encountered antigen.
B and T memory cells remain in the blood for an extended period of time, allowing a faster response in subsequent exposures
Functions of the lymphatic system
Transports antigen presenting cells to secondary lymphoid tissues for antigen recognition and initiation of the adaptive immune system
Produces leukocytes such as B and T lymphocytes in the primary lymphoid tissues
Primary lymphoid tissues and what does itinclude explain
Include the bone marrow and thymus
Bone marrow: where B and T lymphocytes are produced. C lymphocytes remain in the bone marrow until mature.
Thymus: where T lymphocytes travel to mature.
Secondary lymphoid tissues, why are mature B and T cells found in secdnary lymphoid tissue and funcitons of the tonsils, lymhph nodes nad speeln
Include tonsils, lymph nodes and spleen
Mature B and T cells are found here to scan passing lymph for the presence of pathogens or antigen presenting cells.
Lymph nodes are oval or bean-shaped structures, scattered throughout the body, usually in groups, along the length of lymphatic vessels.
Site where antigen presenting cells meet lymphocytes (B and T cells)
TonsilsProduce lymphocytes and well placed to protect against pathogens invading the body
Spleen:Location of clonal selection and expansion of B and T cells. Where initiation of the adaptive immune system occurs
Process of the lymphatic system
- Afferent vessels allow for incoming fluid and the valves prevent backflow
- As lymph passes through the nodes, it filters foreign particles(including pathogens) by trapping them in fibres
- Once trapped, macrophages destroy the foreing substancesby phagocytosis. T cells may destroy directy or B cells may release antibodies to enhance phagocytosis
redblood cell antigen antibiody question
STEPS OF THE ALLERIGC IMMUNE RESPONSE HAD
