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Dentistry Year 2 - Pathology > Introduction to Host Defence > Flashcards

Introduction to Host Defence Flashcards

1
Q

Give a definition of the immune system

A
  • It is a vast communication network of cells and chemical signals
  • Distributed through blood and tissues
  • Regulates normal growth and development of organism
  • Protects against disease
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2
Q

What is the name of the cell that all immune cells originate from?

What two cells does the form?

A

Pluripotent hematopoietic stem cell

Common lymphoid progenitor and common myeloid progenitor

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3
Q

What does the lymphoid progenitor develop into?

What does the myeloid progenitor develop into?

A

Lymphoid progenitor develops lymphoid cells, B, T and natural killer cells.

Myeloid cells differentiate into erythrocytes, neutrophils, macrophages, monocytes, basophils, platelets, dendritic cell.

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4
Q

What is the difference between the primary and secondary lymphoid organ?s

A

primary = thymus for T cells and bone marrow for B cells for maturing to occur

secondary = localised to the site of the infection

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5
Q

Give a definition of immunity

A

Condition/process in humans that permits innate and acquired resistance to disease.

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6
Q

Give the 4 requirements for a effective immune system

A
  1. Must recognise wide range of infections and micro-organisms
  2. Defend against both intracellular and extracellular pathogens
  3. Prevent of limit damage to self
  4. Respond quickly
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7
Q

What two surfaces do microbes need to pass?

A

Skin
External surfaces (athlete’s foot – fungus)
Insect bites (malaria, Lyme)
Trauma (tetanus)

Mucosal membranes
Inhalation (tuberculosis) - infects the lung
Gastrointestinal tract (hepatitis A)
Reproductive tract (HIV, syphilis)

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8
Q

Explain the pathway of the bacterium into the body

A

Bacteria attaches to epithelium.
Starts to cause a local infection.
Immune cells come and target the microbes and takes them to the local lymph node.
B and T cells get activated, move to the site of infection and deal with the infection.

Innate immunity in the first few hours and adaptive after 5 days.

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9
Q

Explain the main barriers provided by the innate immune response

A

Mechanical:
Epithelial cells joined with tight junctions
Flow of air or fluid across
Movement of mucus by cilia.

Chemical:
Mucus and saliva has antimicrobialpeptides (defensins, histatins, cathelicidin) to digest the microbe.
Low pH in stomach
Pepsin enzymes in stomach for digestion

Microbiological:
Commensal flora in the gut to inhabit space

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10
Q

Complement: Innate Immunity

  1. Definition
  2. What are the 3 pathways?
  3. What is the main role for the c3a&c5a, c3a and MAC (C5-9) proteins?
A
  1. System of proteins which are activated to attach to the pathogen surface, recruit inflammatory cells and killing of pathogens
  2. Classical (antigen:antibody complex)
    MB-Lectin (Lectin binding to pathogen surfaces)
    Alternative (Pathogen surfaces)
  3. C3b is deposited on the bacterial surface to make antibodies recognise it (opsonisation).
    C3a & C5a recruit inflammatory cells.
    MAC (C5-9) is amde of 5 proteins and it punches holes in the membrane of the bacteria.
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11
Q

Give the 4 phagocytic cells and where they are

A

Monocytes in blood
Neutrophils in blood
Macrophages in tissue
Dendritic cells in tissues and blood

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12
Q

What are the 5 steps to phagocytosis?

What does the phagocyte bind to?

A
  1. Recruited to site of infection by chemokines and complement
  2. Binds to microbe (pattern recognition and opsonisation)
  3. Internalises microbe into a phagosome
  4. Fusion of phagosome into a phagolysosome
  5. Killing of microbe with nitrogen oxides

Binds to the antibodies

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13
Q

Give an example of when pattern recognition receptors are working

A

Receptors tend to bind to all gram positive or gram negative bacteria. The host has the receptors that recognise patterns on microbes.

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14
Q

What cells bring together the innate and adaptive immunity?

What does this cell do?

A

Dendritic cells

An AntigenPresenting cell which is present in blood and tissues. It captures the microbe and takes it to the lymph node. An immune response is generated here.

  • The antigen is taken up by the dendritic cell and this cell enters the lymphatic system.
  • Dendritic cell enters the lymph node and here will activate the T cells which then go on to activate B cells.
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15
Q

What molecule is needed to present viruses on the dendritic cell?
How about bacteria?

A

Viruses = major-histocompatability complex 1 is needed

Bacteria = major-histocompatability complex 2

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16
Q

Once the major-histocompatabilty complex is presented on the T cell with eh antigen, what cells become activated?

A

MHC 1 activates the cytotoxic T cell (CD8 T cell).

MCH 2 activates the T helper cell (CD4 T cell).

17
Q

Give details on the lymph node and how the dendritic cell acts here

A

Dendritic cells come through the afferent lymphatic vessels.
They go through the cortex of the lymph node where the T cells are (the paracortical area). Dendritic cell activates the T cells.
T cell moves into the germinal center to activate the B cells to make antibodies against the antigen on the dendritic cell.
B and T cells come out the efferent lymphatic vessel and join the cell system.

18
Q

How does the APC activate the T cells?

A

The APC has either MHC 1 or MHC 2.

With MHC 1, it will bind to receptors on the CD8 (Killer cell). These receptors have the CD3 protein on them.

With MHC 2, it binds to CD4 (Helper cell) to activate it. The receptors here have CD3 present also.

19
Q

Explain the mechanism of T cell killing

A

Cytotoxic cell recognises the viral antigen on MHC 1 and releases enzymes and toxins.

(Granzymes instructs the cell to undergo apoptosis.)

20
Q

What does the T helper cell do once activated by the dendritic cell?

A

Becomes one of 4 main cells.

  1. TH1 = activates CD8 killer cells and macrophages
  2. TH2 which activated B cells to produce antibodies
  3. TH17 which recruits neutrophils
  4. Treg which suppresses the immune system
21
Q

What are the two areas on an antibody?

How many antibody type are there?

A

Fc - constant fragment, Fab - antibody binding fragment

5 which are IgG, IgA, IgM, IgE, IgD

22
Q

What are 4 examples of things that can go wrong?

A
  1. Microbes are too clever for the immune system
  2. Cancers growing unchecked
  3. Harmless substances are deemed dangerous
  4. The immune system attacks itself

Dentistry Year 2 - Pathology (25 decks)

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