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Human Biology - Human Body Systems - Level 4 > Immunity > Flashcards

Immunity Flashcards

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1
Q

Immune system

Recognition and Response

A

1) Recognise pathogens
2) Respond appropriately to intruders in a way that protects body
3) Respond next time intruders are encountered

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2
Q

Homeostasis and Immune System

A

Removes worn out cells

Identification of abnormal cells

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3
Q

Types of Body Defense Mechanisms

A

Physical barriers - first line of defence

Immune System

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4
Q

Body Defense Mechanisms

Physical Barrier

A
  • Skin
  • Mucous membranes (mouth, nose, etc.)
  • Mucus & cilia of airways
  • Acids, enzymes and cell shedding of digestive system.
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5
Q

Body Defense Mechanisms

Immune System

A

Second line of defense
Slower response
More effective
Can provide memory

Circulating cells that respond to pathogens
Inflammation
Fever
‘Acquired Immunity’

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6
Q

Types of Immunity

A

Innate Immunity
Passive Immunity
Adaptive (active immunity)
Hard Immunity / Indirect Protection

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7
Q

What is innate immunity?

A
  • Born with, always present, non-selective response.
  • Non-specific
  • Includes external barrier, cough reflex, lysosome.
  • Rapid and independent of antigen (non-specific).
  • Relies on recognition of types of molecules common to many pathogens but absent in the host to stimulate inflammatory response and phagocytosis.
    e. g. Formylated methioniene, used as initiation amino acid in prokaryotes, Extremely potent chemoattractant for neutrophils
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8
Q

What is Passive Immunity?

A
  • ‘Borrowed’ from another individual
  • Ready made
  • Natural e.g. across placenta / breast milk
  • Artificial e.g. short term immunisation, transfer of fully functioning antibodies, immediate protection, body does not develop memory.
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9
Q

What is Adaptive (Active) Immunity?

A
  • Develops through our lives
  • As we are exposed to disease (or immunised)
  • Specific response via antibody production
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10
Q

What is Hard Immunity / Indirect Protection?

A
  • Can only occur when a significant proportion of the population are immune / vaccinated.
  • Arises due to a lack of susceptible hosts, causing disease to die down.
  • Particularly important to provide immunity to vulnerable people who cannot otherwise be vaccinated.
    e. g. children / immunocompromised.
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11
Q

What are antigens?

A

Antibody generating.

Molecules (often proteins, glycoproteins or polysaccharides) on the plasma membrane that produce immune response.

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12
Q

What are Antibodies? (Ab)

A
  • Proteins secreted by immune cells in response to an antigen.
  • Have a unique specific antigen-binding site.
  • Leads to destruction of antigen-bearing cell.
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13
Q

How do Antibodies work?

A

Attach to antigens and ‘tag’ the pathogen.

Makes it more visible to other cells.

(Killer T and phagocytes) = neutralisation
Antibodies are highly specific.

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14
Q

Process of Antibodies

A

Agglutination: make pathogens clump together.

Antitoxins: Neutralise the toxins produced by bacteria.

Lysis: digests bacterial membrane

Opsorisation: coats pathogen in protein that identifies as foreign.

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15
Q

What produces antibodies?

A

B-lymphocytes

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16
Q

Components of the Immune System

Innate Immune System

A
  • Response is non-specific
  • Exposure leads to immediate maximal response
  • Cell-mediated and humoral components
  • No immunological memory
  • Found in nearly all forms of life (plants + animals)
17
Q

Components of the Immune System

Adaptive Immune System

A
  • Pathogen and antigen specific response
  • Lag time between exposure and maximal response.
  • Cell-mediated and humoral components
  • Exposure leads to immunologic memory
  • Found only in javed vertebraes
18
Q

What is Cell Mediated Immunity?

A

Direct attack by activated T cells.

React with foreign antigens on the surface of other host cells.

19
Q

What is antibody-mediated (humoral) Immunity?

A

Attack by circulating antibodies, released by the plasma cells.

Derived from activated B cells.

20
Q

How does Humoral Immunity work?

A

1) Neutralisation
2) Lysis by the complement system
3) Phagocytosis + Destruction

21
Q

How does Cell Mediated Immunity work?

A

Involves T-cell recognition of abnormal antigens on the surface of host cells (indicating viral infection or tumorigenic change) and the killing of infected cells.

22
Q

How does innate immunity work?

A

Dominant system of host defence in most organisms.

  • Inflammation (one of) is first response:
  • Redness, swelling and pain
  • Chemical and cellular response
  • During acute phase of inflammation, particularly result of bacterial infection - neutrophils migrate towards the site of inflammation in a process called chemotaxis, and are usually the first cells to arrive at infection.
23
Q

How the body deals with infection:

A

1) Break in skin introduces bacteria. Activated macrophages (derived from monocytes) engulf the pathogens and release cytokines and chemotoxins.
2) Activated mass cells release histamine.
3) Histamine and cytokines dilate local blood vessels and increase their permeability. Cytokines also make the blood vessel wall sticky, causing neutrophils to attack.
4) Chemotoxins attract neutrophils, which pass between the endothelial cells and migrate to the site of infection.
5) Neutrophils engulf pathogens by phagocytosis and destroy them.

24
Q

Cells of Adaptive Immune Response

A

Lymphocytes: large nuclei with little cytoplasm

T Cells: Thymus dependent
B Cells: Bone marrow derived

25
Q

What are T Cells?

A

Directly destroy virus infected cells and mutant cells by release chemicals:

  • cytokines
  • chemokines
26
Q

What are B Cells?

A

Transformed into plasma cells, which secrete antibodies that indirectly lead to destruction of foreign cells.

27
Q

What are B Lymphocytes?

A
  • As the activated B cell then begins to divide (clonal expansion) its offspring secrete millions of copies of that antibody that recognises the antigen.
  • These pathogens circulate the blood plasma and in lymph, bind to pathogens expressing the antigen and mark them for destruction by complement activation or for uptake and destruction by phagocytes.
28
Q

How do antibodies neutralise threats directly?

A

By binding to bacterial toxins or by interfering with with the receptors that viruses and bacteria use to infect cells.

29
Q

What is the adaptive immune system?

A

1) Antigen presentation
2) Clonal selection
3) Clonal expansion

30
Q

What is the antigen presentation?

A

1) Macrophage engulfs invading organism by endocytosis (phagocytosis).
2) The non-self antigens are presented on to the plasma membrane of the macrophage.

31
Q

What is Clonal Selection?

A
  • The macrophages (monocytes + granulocytes)
  • Helper T-cells (lymphocytes)
  • Through complementary binding of receptors and antigens.
  • The B-lymphocyte and a T-helper lymphocyte attach to the macrophage.
  • The lymphocytes have complementary receptors to the non-self antigen.
32
Q

What is Clonal Expansion?

A
  • T-helper cells secrete cytokines
  • This activates B-cells
  • to divide by mitosis
  • Producing a large number of identical cells, hence clones.
33
Q

How are clones produced?

A

The t-helper cells stimulate the selected B-lymphocyte to divide by mitosis.

Produces clones of identical B-lymphocytes.

34
Q

What are cloned B-lymphocytes

A
  • A large number of identical B-lymphocytes
  • Called plasma cells
  • All producing antibodies
  • All able to destroy this particular pathogen
35
Q

What is the secondary response?

A
  • Clonal expansion produced plasma cells and a few memory B-cells.
  • Remain in body
  • When same antigen is identified; these memory cells rapidly produce more plasma cells appropriately antibody.
  • Enables fast response to an infection by the same invader.
36
Q

What is immunological memory?

A
  • Plasma and T-cells die after a few days
  • Memory B cells and Memory T cells survive
  • Each memory cell can only recognise the specific antigen already defeated.

Upon secondary infection an immune response is quicker and more powerful.

37
Q

Problems with the Immune System?

A

1) Hypersensitivity - e.g. allergies
2) Immunodeficiency - cannot mount effective response e.g. genetic (SCID) or induced by disease (i.e. HIV infection, immunosuppressant drugs, malnutrition.
3) Autoimmune diseases - Immune system makes inappropriate immune response e.g. lupus, rheumatoid arthritis, insulin-dependent diabetes, M.S.

38
Q

Using the Immune System to Protect

A
  • Vaccinations
  • Immune system remembers the pathogens to which it has been exposed.
  • Can respond quickly and effectively next time.
  • Inactive pathogens (killed / weakened)

Human Biology - Human Body Systems - Level 4 (6 decks)

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