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Biology > Unit 3 AOS 2: Immunity > Flashcards

Unit 3 AOS 2: Immunity Flashcards

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1
Q

Immunity

A

The ability of an organism to resist infection.

Immunity to a disease is achieved through the presence of antibodies to that disease in a person’s system.

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2
Q

Pathogen

Define
2 types
Examples

A

An organism that causes disease in another organism.

A pathogen is defined as an organism causing disease to its host, with the severity of the disease symptoms referred to as virulence

Cellular pathogens: have a cellular structure and are living organisms
Non-cellular pathogens: do not have a cellular structure and are non-living

E.g.

  • bacteria
  • fungi
  • worms
  • protozoa
  • viruses
  • prions
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3
Q

Antigen

A

A molecule whose shape triggers the production of antibodies (immunoglobulins) that will bind to the antigen. A foreign substance capable of triggering an immune response in an organism.

There are two types:

  • self-antigen
  • non-self antigen
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4
Q

Self-antigen

A
  • they are normal body cells and substances that don’t usually stimulate an immune response
  • they mark cells of an organism as ‘self’ so that they are immune
  • most important self-antigens take the form of MHC proteins
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5
Q

Non-self antigen

A
  • the cells that that do not originate in your body
  • foreign antigens can exist as many different types of molecules, including proteins, sugars, and DNA/RNA

E.g. allergens

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6
Q

Innate Immune Response

A
  • The innate immune responses are the first line of defence against invading pathogens.
  • They are also required to initiate specific adaptive immune responses. Innate immune responses rely on the body’s ability to recognise conserved features of pathogens that are not present in the uninfected host.
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7
Q

The first line of defence

A
  • The first line of defence is your innate immune system.
  • Involves 3 types of barriers such as physical, chemical and microbiological
  • Physical: barriers that block pathogens from entering the organism
    E.g. intact skin, mucous, eyelashes
  • Chemical: barriers that work by producing chemical substances that make an environment unliveable for a pathogen
    E.g. stomach acid, antibacterial proteins, acidic sweat, lysozyme enzymes
  • Microbiological: the presence of non-pathogenic bacteria in the body can prevent the growth of pathogenic bacteria as they compete for space and resources
    E.g. non-pathogenic organisms, presence of bacteria on the skin
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8
Q

The first line of defence
Barriers in plants

Physical and chemical

A

Physical: barriers that prevent pathogens from entering the organism
- Waxy cuticles of leaves
- Thick bark
- Formation of galls
- Vertically hanging leaves: Prevent accumulation of moisture on leaf surfaces, inhibiting pathogens that
requires water to move
- Hair and Thorns​: Deters pathogens by reducing available surface area to attach

Chemical: barriers that involve the production of chemicals that can be toxins that are harmful to pathogens
- Toxins: Deter pathogens or digest them when they come into contact
- Shedding infected leaves and branches: Release chemicals that cause leaves and branches to drop
prevents further infection
- Wetting agents: Destroy fungal cell membranes
- Defensins: Reduce membrane permeability and inhibit the action of enzymes and ribosomes

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9
Q

The second line of defence

A
  • The second line of defence is a nonspecific resistance that destroys invaders in a generalised way without targeting specific individuals:

➔ Part of the innate immune system - meaning, its components response in the same way regardless of the type of pathogen or antigen present
➔ Responds to injury or antigens extremely quickly. Within minutes to hours, it starts working to limit the spread of infection around the body

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10
Q

Neutrophils

A

Phagocytosis of pathogens

  • Found in blood vessels and the most numerous cell in the immune system.
  • They are phagocytes, which means they engulf and destroy pathogens​.
  • They die quickly, in large numbers and become pus, forming a protective covering on the skin. They ​respond to inflammatory signals​.
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11
Q

Macrophages

A

Phagocytosis of pathogens and antigen presentation to the adaptive immune system

  • Found in the blood and lymph, macrophages contain both MHC I and II markers​.
  • They detect foreign antigens and phagocytise them, then present these antigens of their MHC II.
  • They transport these antigens to the lymph to initiate the third line of defence.
  • They mature from monocytes.
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12
Q

Dendritic Cells

A

Phagocytosis of pathogens and antigen presentation to the adaptive immune response

  • Phagocytes with long membranous extensions.
  • They engulf foreign material and present the foreign markers to other immune cells.
  • Has a key role in the activation of the 3rd Line of defence.
  • Act on the surfaces of the body eg, Eyes, mucous, skin, Intestine surface

Due to high surface area, they are able to engulf pathogens, after detecting them with their MHC I, and present their antigens on their MHC II then transport them to the lymph, initiating the adaptive immune response

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13
Q

Mast cells

A

Causes inflammation by the release of histamine

  • Detect damage in nearby cells and produces histamine if the damage is detected. This causes blood vessels to dilate and makes cell walls more permeable, this allows white blood cells and plasma to flow to the function site easily.
  • Attracts phagocytes
  • located in connective tissues
  • Leukocytes
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14
Q

Complement proteins

A
  • Is a system of 30 different blood proteins that act together to create three responses
    1. Opsonize pathogens: Stick on the surface of a pathogen and make it easier for immune cells(phagocytes) to identify the foreign material.
    2. Attract phagocytes: Phagocytes are drawn to the source of the compliment bacteria
    3. Create pores in bacterial membranes (MAC): This pore causes the bacteria to rupture.
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15
Q

Cytokines

A

Any of a number of substances, such as interferon, interleukin, and growth factors, which are secreted by certain cells of the immune system and have an effect on other cells.

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16
Q

Cytokines

Interleukin 1 and 2

A

A type of cytokine that assists in the coordination of cells within the immune response.

Interleukin 1: A cytokine that mediates various inflammatory activities. Production of mature IL-1 requires caspase activity.

Interleukin 2: made by a type of T lymphocyte. It increases the growth and activity of other T lymphocytes and B lymphocytes, and affects the development of the immune system.

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17
Q

Cytokines

Interferons

A

A type of cytokine produced by cells in the immune system in response to foreign antigens and tumors. They act on uninfected cells to make them more resistant to infection. They are produced early in a viral infection.

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18
Q

Inflammatory Response

A
  • The inflammatory response is designed to eliminate the effects of an injury, clear out cells that may have been damaged or destroyed, and initiate repair
  • This process increases blood flow to the injured area, bringing out a greater number of immune cells and components to help fight pathogens, which leads to swelling, redness, and heat.

The enhanced blood flow & vessel permeability of nearby capillaries aids in delivering clotting elements to the injured area.
Clotting is the beginning of the healing process and stops the spread of microbes.
The enhanced blood flow & vessel permeability of nearby capillaries also increases the migration of phagocytotic cells from the blood into the injured tissue, where they can engulf foreign material.

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19
Q

Lymphatic system

A

A large network of vessels throughout the body through which lymph flows.

  • The lymphatic system is a core component of the body’s immune system. One of its main function is:
  • The transportation of antigen-presenting cells to secondary lymphoid tissues for antigen recognition and initiation of the adaptive immune response
  • Drains lymph (fluid surrounding cells) towards the heart, to be pumped back through the circulatory system.
  • It only goes one way.
  • T-cells mature in the thyroid gland, and B cells mature in the bone marrow.
    The vast majority of B cells and Th cells are found in lymph nodes. Typically, this is where they bind their antigen. B and T cells travel throughout lymph and blood to reach damaged or infected areas. Antibodies released by activated B cells also travel primarily through the lymph system.
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20
Q

Adaptive Immunity

Define
2 key components of differentiation from 2nd line of defence

A

The adaptive immune system, also referred as the acquired immune system, is a subsystem of the immune system that is composed of specialised, systemic cells and processes that eliminate pathogens or prevent their growth.

1) Specificity
The adaptive immune system responds to each type of pathogen in a highly tailored way
2) The Formation of Immunological Memory
The adaptive immune system results in the creation of the cells that allow the body to response to future re-infections by a previously encountered pathogen more quickly and effectively

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21
Q

Third line of defence

A
  • The third line of defence is called the immune response and is SPECIFIC.
  • It involves the production of two types of lymphocytes (B and T cells) which are specific to the invading particle.
  • They work together to attack the pathogen.
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22
Q

Cell-mediated immune response

A
  • Cell-mediated immunity is an immune response that does not involve antibodies.
  • Rather, cell-mediated immunity is the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.
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23
Q 
Cell-mediated immune response
Th cells (lymphocyte)
A

Assist other lymphocytes to perform their roles; recognise antigens presented on antigen presenting cells; mature in thymus

A type of immune cell that stimulates killer T cells, macrophages, and B cells to make immune responses. A helper T cell is a type of white blood cell and a type of lymphocyte.

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24
Q

Cell-mediated immune response

Antigen-presenting cells

A

A type of immune cell that boosts immune responses by showing antigens on its surface to other cells of the immune system. An antigen-presenting cell is a type of phagocyte. Also called APC.

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25
Q

Cell-mediated immune response

MHC 2 Markers

A

Proteins that bind to and “present” proteins of foreign substances on the surface of cells for recognition by other immune cells.

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26
Q

Cell-mediated immune response

Phagocytes

A

Large white blood cells contribute to the immune defences by ingesting microbes, other cells, and foreign particles. The two principal phagocytes are neutrophils and monocytes. They emigrate out of the blood and into tissues in which an infection has developed.

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27
Q

Cell-mediated immune response

Lymph nodes

A

Small bean-shaped structures scattered along the vessels of the lymphatic system. The lymph nodes produce white blood cells and filter bacteria and cancer cells that may travel through the system.

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28
Q

Cell-mediated immune response

Cytokine involvement

A

Cytokines are released in response to an antigen in this immune response

29
Q

Cell-mediated immune response

Cytotoxic t cells (and NK cells)

A

Destroying virally infected or cancerous cells; Mature in the thymus

T lymphocyte responsible for attacking cancerous host cells or cells infected with an invading bacterium or virus.

30
Q

Memory T cells

A

Memory T cells are antigen-specific T cells that remain long-term after an infection has been eliminated. The memory T cells are quickly converted into large numbers of effector T cells upon reexposure to the specific invading antigen, thus providing a rapid response to past infection.

31
Q

Humoral immune response

A
  • Involves the neutralisation and/or destruction of a pathogen via the production and secretion of antibodies.
  • Immune response response involving B lymphocytes that produce specific antibodies against foreign antigens.

The Humoral immune response is ​brought about by B cells​ which produce an array of different antibodies that
attack foreign antigens. ​B cells, which produce a range of antibodies that circulate in the blood and lymph​

32
Q

Humoral immunity will be activated when:

A
  • A naïve B cell will bind to a free antigen.
  • A Th cell will be presented with its antigen on a MHC2 molecule by an APC (macrophage or dendritic cell).
  • The ‘selected’ B cell and Th cell will then find each other and if they have bound the same antigen, the Th cell will release cytokines.
  • These cytokines cause the B cell to divide (proliferate) and differentiate into B memory cells and B plasma cells. (A type of paracrine signalling)
  • These cytokines also cause the Th cell to divide (proliferate) and differentiate into Th memory cells and Th active cells.
  • The memory cells remain in the body to fight subsequent infection by a pathogen with the same antigen specificity and the B plasma and Th active cells fight off the current infection.
33
Q

Naive B cell

A

B cells that have not yet bound their antigen. They have antibodies bound in their plasma membrane that act as receptors.

34
Q

Activated B cell

A

B cells are activated when their B cell receptor (BCR) binds to either soluble or membrane bound antigen. Once activated B cells may undergo class switch recombination.

35
Q

Clonal selection

Humoral immune response

A

The theory that in a group of lymphocytes, a specific antigen will activate only the lymphocyte that has a receptor that specifically recognises it. This lymphocyte will proliferate into clones of itself.

36
Q

Differentiation

Humoral immune response

A

The changes of the structure and function of a cell that occurs during its development

37
Q

Proliferation

Humoral immune response

A

to grow or multiply by rapidly producing new tissue, parts, cells, buds, or offspring.

38
Q

Clonal expansion

Humoral immune response

A

Clonal expansion is the process by which daughter cells arise from a parent cell. During B cell clonal expansion, many copies of that B cell are produced that share affinity with and specificity of the same antigen.

39
Q

Memory B cells

A

They are identical to naïve B cells; however, they are produced as a result of a B cell being selected. They remain in the body to defend against infection by a pathogen with the same antigen specificity.

40
Q

Plasma cells

A

Plasma cells develop from B cells that have been activated. A plasma cell is a type of white blood cell. Also called plasmacyte.

41
Q

Humoral immune response

Antibodies structure, types and function

A

Antibodies are also known as B cell receptors. They are released in large quantities by plasma B cells when a person is infected. They have two binding sites with identical antigen specificity.
There are 5 types:
IgG: The most common antibody, they can cross the placenta. Responsible for activation complement proteins and can neutralise a toxin directly; most commonly passed from mother to baby
IgE: Helps initiate inflamation after a pathogenic infection; also causes allergic reactions to non-pathogenic agents
IgA: Neutralise pathogens in respiratory, digestive and reproductive tracts
IgM: Usually the first secreted in response to an infection; Cause aggultination of cells containing antigens and making them more easily eliminated by phagocytes
IgD: Found on the plasma membrane of B cells, as B cell receptors; Not secreted into circulation

42
Q

Acquired immunity

Active

A

Immunity formed by stimulation of the immune system by antigens; results in generation of effectors and memory cells

43
Q

Acquired immunity

Passive

A

Transfer of antibodies from one individual to another; does not generate immunological memory

44
Q

Acquired immunity
Active natural
Active artificial

A

Natural: Exposure to pathogen; Introduces active antigens, in order to generate an immune response

Artificial: Vaccines; Introduces inactive antigens to the body, in order to generate an immune response

45
Q

Acquired immunity
Passive natural
Passive artificial

A

Natural: Transfer of antibodies from mother to feotus via placenta or breast milk

Artificial: The administration, usually by injection, of antibodies produced by another organism to provide an immediate, specific immune response.

46
Q

Vaccination

A

Injection of a killed microbe in order to stimulate the immune system against the microbe, thereby preventing disease

Vaccines rely on the adaptive immune system of generate immunity, then often take days or weeks to confer immunity

47
Q

Herd immunity

A
  • protection conferred to non-immune individuals when a high percentage of the population is immune to the same disease
  • can often be achieved through high vaccination rates
48
Q

Immunodeficiencies

A

A state in which an individual’s immune system is unable to combat pathogens effectively. As a result of this, people with an immunodeficiency are more susceptible to infections.

49
Q

HIV/AIDS

A

HIV: A viral blood-borne infection that targets immune cells, particularly helper T cells, and destroys them, eventually leading to an acquired immunodeficiency

AIDS: A life-threatening condition caused by an untreated infection with the human immunodeficiency virus (HIV) in which an individual’s immune system is no longer able to function normally

50
Q

Multiple sclerosis

A

Involves an immune-mediated process in which an abnormal response of the body’s immune system is directed against the central nervous system

51
Q

Allergy

A

A cluster of syndromes experienced by a person who has had an allergic reaction

52
Q

Allergy

Allergen

A

A non-pathogenic antigen that triggers an allergic reaction

53
Q

Allergy

Histamine

A

A chemical found in some of the body’s cells - causes many of the symptoms of allergies, such as a runny nose or sneezing.
When a person is allergic to a particular substance, such as a food or dust, the immune system mistakenly believes that this usually harmless substance is actually harmful to the body.

54
Q

Monoclonal antibodies

A
  • The unique immunoglobulin antibody produced by a clone of cells derived from a fusion of a B lymphocyte with a myeloma cell
  • Type of passive artificial immunity

➔ Monoclonal = Refers to creating many identical copies of a single cell
➔ Antibody = Are protein molecules produced by plasma that contain highly specific antigen-binding sites

55
Q

Allergens

A
  • Antigens that the immune system recognise as non-self
  • Initiate a strong immune system response
  • Aren’t pathogens and can’t cause bodily harm
  • The immune response they generate, therefore, is unwarranted and is what we call an allergic reaction
56
Q

Natural killer cell

A

Destroys infected or abnormal cells via induction of apoptosis

  • When a cell becomes infected with a virus, antigens from the virus remain on the surface of the host cell.
  • Natural killer cells recognise these viral antigens, and release cytotoxic chemicals that disrupt the infected cell’s membranes, triggering apoptosis.
57
Q 
Inflammatory response
(IVM)
Initiation
Vasodilation
Migration
A

Initiation:
- in response to injury, damaged cells release cytokines and mast cells degranulate, releasing histamine

Vasodilation:

  • the histamine released from mast cells travels to nearby blood vessels where it causes vasodilation
  • this means the blood vessels become bigger and the vessel walls become more permeable through the formation of gaps
  • therefore increasing blood flow to the area

Migration:

  • vasodilation and the increased leakiness of blood vessels allow for a number of innate immune system components to leave the bloodstream and enter the site of injury
  • this response continues until the site has been cleared of pathogens and debris and the site of injury has been healed
58
Q

Initiation of the Adaptive Immune Response

A
  • A key process in the initiation of the two adaptive immune responses is the selection of a T lymphocyte called a T helper cell via a process called antigen presentation
  • After engulfing and digesting a pathogen, antigen-presenting cells (APCs) present foreign antigens on their surface using MHC II proteins.
  • This complex interacts with T cell receptors on the surface of T helper cells, each of which displays a T cell receptor that is slightly different in shape.
  • When an APC presents an antigen to a T helper cell that is complementary in shape to the T cell receptor, that T helper cell becomes activated. This activated T helper cell then helps initiate the process of humoral and cell-mediated immunity
59
Q

Antibodies

A

Proteins compromised of 4 polypeptide chains, including the two heavy chains and two light chains

Each antibody has 2 identical antigen-binding sites that allow it to bind with antigens on the surface of 2 different pathogens at once

60
Q

Immunological memory

A

B memory cells and T memory cells formed during the adaptive immune response stay in the blood for extended periods of time, allowing the body to respond to pathogens it previously encountered quickly and effectively

61
Q

Lymphatic system

Primary lymphoid tissues

Definition
Structures
Functions

A

Primary lymphoid tissues:
- Primary lymphoid tissues are responsible for the creation and maturation of lymphocytes.
➔The main primary lymphoid tissues are bone marrow and the thymus.

Structure: Bone marrow
Function: Production of immature B and T cells, and maturation of B cells

Structure: Thymus
Function: Maturation of T cells

62
Q

Lymphatic system

Secondary lymphoid tissues

A

Secondary lymphoid tissues are responsible for maintaining mature lymphocytes and initiating the adaptive immune response.
- In these tissues, mature lymphocytes are clustered together and ‘scan’ the lymph for the presence of any pathogens or foreign antigens that match their receptors, undergoing clonal selection and differentiation when encountering a matching antigen

Structure: Lymph nodes and Spleen
Function: Site where PACs meet lymphocytes, and the Location of clonal selection and expansion of T and B cells, and initiation of the adaptive immune response.

63
Q

Vaccine

First dose vs Second dose
graph

A

➔ The first vaccination generates a primary immune response. This response creates a moderate level of antibodies and memory cells
➔ The second vaccination triggers the memory cells created by the first vaccine, resulting in a secondary immune response. This response occurs extremely quickly and results in the rapid creation of a larger number of antibodies and memory cells
Another form of vaccination is a booster vaccine.
- Given to people who have received a vaccine a long time ago
Booster vaccines produce more memory B and T cells, increasing a person’s immunity to an adequate level
★ Seperate to vaccination programs
➔ Given much later to initial vaccination

64
Q 
Examples of immunity
1 - natural active immunity
2 - natural passive immunity
3 - artificial active immunity
4 - artificial passive immunity
A
  1. Getting chicken pox and being immune to it afterwards
  2. Antibodies passing from mother to baby in breast milk or across the placenta
  3. Vaccines, such as against measles and polio
  4. Being injected with antibodies, such as anti-D antibodies for Rhesus-negative mothers
65
Q

Autoimmune diseases

How they work

A

Autoimmune diseases occur when the body’s adaptive immune system recognises self-tissues as foreign and launches an immune response against them.
➔ Lymphocytes don’t recognise self-markers and end up acting as self-cells

  • Autoimmune diseases occur when the body’s adaptive immune system recognises self-tissues as foreign and launches an immune response against them.
  • An example of an autoimmune disease is multiple sclerosis, in which the myelin sheath surrounding nerve cells is broken down by T cells.
66
Q

Cause of Autoimmune diseases

A

Failure of Clonal Detection
- Clonal deletion is a process that occurs during the development and maturation of B and T lymphocytes. It involves the presentation of self-antigens to lymphocytes whilst they are still in the primary lymphoid tissues (bone marrow for B cells and the thymus for T cells). Any lymphocyte that responds to the self-antigen is destroyed, protecting the host against autoimmunity.

The Hygiene Hypothesis:
- Improvements to sanitation and hygiene over the past century have meant that children nowadays are exposed to far fewer antigens and pathogens when they’re young. According to the hygiene hypothesis, this low exposure to non-self antigens results in an overactive immune system later in life that can cause autoimmune diseases to develop, as well as allergies and other inflammatory diseases.

67
Q

Management of Autoimmune diseases

A

Two broad mechanisms of treating autoimmune diseases are:
● Filtration of autoantibodies from the blood. By removing autoantibodies from a patient’s bloodstream the underlying tissue destruction causing a person’s autoimmune disease should cease.
● Immunosuppression. By deliberately reducing the activation and effectiveness of a person’s immune system, their lymphocytes will be less able to recognise and attack self-tissues. Of course, if too much immunosuppression occurs the individual may develop an immune deficiency

68
Q

Allergic reactions

How they work

A

Allergic reactions occur when the body’s immune system is activated by a non-pathogenic antigen. They are initiated by histamine released from mast cells after IgE antibodies have bound to an antigen
➔ Non-pathogenic antigens are recognised by the immune system as foreign and result an immune response
➔ Symptoms are known as allergies

Biology (18 decks)

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