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Medicine Phase 2a > Immunology (Peer-Teaching) > Flashcards

Immunology (Peer-Teaching) Flashcards

1
Q

Give 4 examples of lymphoid organs

A

Lymph nodes
Spleen
Thymus
Diffuse lymphoid tissue (e.g. mucosa associated lymphoid tissue - MALTS)

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2
Q

Give 2 examples of MALTs

A

Tonsils
Peyers Patches
(Mucosa Associated Lymphoid Tissue)

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3
Q

Where are lymph nodes abundant

A

Neck
Armpit
Groin

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4
Q

What cells can be found in the lymph nodes

A

Macrophages (that phagocytose foreign substances)
T cells (that directly attack pathogens)
Circulating cells
Dendritic cells

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5
Q

Define dendritic cell

A

A special type of cell that is a key regulator of the immune system, acting as a professional antigen-presenting cell (APC) capable of activating naive T cells and stimulating the growth and differentiation of B cells..

Found in lymph nodes and spleen.

Dendritic means ‘tree-like branching’

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6
Q

In spleen, what happens in the white pulp?

A
  • Filtering out antibody-coated bacteria
  • Antibodies are made by B cells
  • Filters blood
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7
Q

In spleen, what happens in the red pulp?

A

Old blood cells are destroyed

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8
Q

In which periods of time is thymus most active

A

Neonatal and Pre-adolescent periods

Atrophies after puberty

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9
Q

What is thymus involved in?

A

Development of T cells

also Destroys T cells that react to self-antigens

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10
Q

Describe features of Innate Immunity

A 
Present at birth
Non-specific
No memory
Barriers (e.g.skin)
Limited number of receptors e.g. TLR, NLR
Involves:
Phagocytes (neutrophils, macrophages and dendritic cells)
NK cells
Basophils
Eosinophils
Complement proteins
PAMPs
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11
Q

Describe features of adaptive immunity

A

Built up over time
Specific
Memory (to previous disease/vaccinations)
Lymphoid organs (lymph nodes, spleen, thymus)
Lymphocytes (T and B cells)
Antibodies
Epitopes
Receptor diversity requires somatic mutation

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12
Q

Describe the first line of defence of innate immunity

A

Intact skin
Mucous membranes and their secretions
Normal microbiota

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13
Q

Describe the second line of defence of innate immunity

A
  • Phagocytes such as neutrophils, eosinophils, dendritic cells and macrophages
  • Inflammation
  • Fever
  • Antimicrobial substances
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14
Q

What are 2 different types of PRRs?

Give 2 examples for each

A
  • Secreting and circulating e.g. lectins (mannose binding lectin) and collectins
  • Cell associated e.g. toll-like receptors, nod-like receptors
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15
Q

What do PRRs (pattern recognition receptors) recognise?

A

PAMPs (pathogen associated molecular patterns)

DAMPs (damage associated..)

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16
Q

Give example of PAMP

A

Lipopolysaccharides (LPS) such as endotoxins on gram negative bacteria

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17
Q

What is the purpose of PRRs?

A

Trigger the innate immune response and inflammatory response.

Function to opsonise the pathogen
Activate complement e.g. mannose binding lectin
Activate inflammatory mediators
Secrete interferons and pro-inflammatory cytokines
Induce apoptosis of infected cells

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18
Q

What are 3 different methods of complement activation

A

Classical pathway - antigen-antibody immune complexes

Alternative pathway - foreign surfaces - antigens

Lectin pathway - mannose-binding lectin - mannose residues on pathogen surface

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19
Q

What are mechanisms of action of the complement system?

A

C3b is deposite on microbe then:

Lyse microbes directly (MAC-membrane attack complex formed)

Increase chemotaxis (C3a and C5a) and inflammatory response
--recruitment and activation of leukocytes

Opsonisation - increasing phagocytosis (C3b)
–recognise bound C3b by phagocyte C3b receptor

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20
Q

Describe process of phagocytosis

A
  • Chemotaxis and adherence of microbe to phagocyte
  • Ingestion of microbe by phagocyte
  • Formation of a phagosome
  • Fusion of the phagosome with a lysosome to form a phagolysosome
  • Digestion of ingested microbe by enzymes
  • Formation of residual body containing indigestible material
  • Discharge of waste materials
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21
Q

What is role of natural killer cells

A

Kill your own cells (through apoptosis) if infected with viruses or have become cancerous

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22
Q

What is released by mast cells once activated?

A

Histamine and Heparin

also chemokines and cytokines

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23
Q

How does histamine cause the characteristic signs of inflammation

A

Dilates blood vessels

Also recruits neutrophils and macrophages

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24
Q

What are basophils typically associated with

A

Hypersensitivity reactions and Parasitic infections

Also releases histamine

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25
Q

When is the concentration of eosinophils raised?

A

Allergy or Parasitic infections

26
Q

What is the difference between Humoral and cell-mediated immunity

A

Humoral is antibody mediated and involves extarcellular antigens
Cell Mediated involves intracellular antigens

27
Q

Describe process of Humoral Immune system

A

(Antibody -Mediated)

  • B cells binds to extracellular antigen for which it is specific. Usually requires cooperation from T helper cell
  • B cell oftern with stimulation from a T ehlper cell, differentiates into a plasma cell
  • Plasma cells proliferate and produce antibodies against the antigen.

(Alternatively the B cell can differentiate into a memory cell)

28
Q

Describe Cell-mediated immune system

A

Intracellular antigens expressed on the surface of a cell infected by a virus, bacterium or parasite. (Also may be expressed on surface of an APC)

  • T cell binds to MHC-antigen complexes on the surface of the infected cell, activating the t cell (with its cytokine receptors).
  • A T-helper cell produces cytokines that cause the activated T cell to differentiate into a cytotoxic T cell. These cytokines also influence the formation of plasma cells and activated macrophages.
  • Infected target cell is lysed by the cytotoxic T cell.
29
Q

Define foreign antigen

A

Large signalling molecules not normally found in the body that act as flags to adaptive immune system.
E.g. bacterium, virus, fungus, toxin or diseased cell within body.

30
Q

What is purpose of Antigen presenting cell

A

Present antigens to T cells

31
Q

Give 3 examples of antigen presenting cells

A

Macrophages
Dendritic cells
B cells

32
Q

What are MHCs (major histocompatibilty complexes)?

A

Proteins that mark a cell as self
Class 1 - all cells
Class 2 -APCs

33
Q

Describe briefly function of MHC

A

Antigen associates with MHC molecule and they are presented on cell surface
T cell recognises combination and antigen.

34
Q

Which class of MHC and which T cell is associated with APCs

A

Class II MHC

Helper T cell

35
Q

Which T cell is associated with an infected cell presenting Class I MHC molecule?

A

Cytotoxic T cell

36
Q

What is role of T helper cells

A

Stimulate proliferation of other T cells

Stimulate B cells to produce antibodies

37
Q

What T cells bind to antigens presented on Class II MHC

What type of antigens are these

A

CD4 T helper

Extrinsic/extracellular (phagocytosis)

38
Q

What T cells bind to antigens presented on Class I MHC

What type of antigens are these

A

CD8 T cytotoxic

Intrinsic/intracellular (e.g. virus)

39
Q

What is purpose of cytotoxic T cells

A

Destroy infected body cells (apoptosis)

40
Q

What is function of B cells

A

Recognise SOLUBLE antigens in blood

produce antibodies

41
Q

Describe B lymphocyte activation

A
  • B lymphocytes travel to lymph nodes
  • They proliferate via clonal expansion
  • Differentiate into:
    • Plasma cells which produce antibodies
    • Memory B cells to ward off future infection
42
Q

On antibody which part is Fc region and what does it bind to?

A

(Imagine Y shape)
Vertical downward part that is only part of heavy chain is Fc region.
Binds to Fc receptor on phagocyte

43
Q

Give examples of dendritic cells specialised to an organ

A

Kupffer cells - liver

Langerhans cells - skin

44
Q

What is the Fab fragment

A

Region on antibody that binds to antigens

45
Q

What is epitope

A

Part of the antigen that binds to the Fab fragment

46
Q

Which immunoglobulins can NOT cross the placenta?

A

IgM and IgD

47
Q

Which immunoglobulin can cross the placenta?

A

IgG (passive immunity to fetus)

48
Q

Which immunoglobulin is 1st response to antigen?

A

IgM

49
Q

Which Ig is most common

A

IgG

50
Q

Which Ig is involved in Histamine reactions and allergies (mast cells, basophils)

A

IgE

51
Q

Which Ig is involved in B cell activation

A

IgD

52
Q

Which Ig is secreted from mucous membranes?

A

IgA

also in colostrum

53
Q

Which Ig is most common in early stages/primary response of fighting non-self antigen

A

IgM

54
Q

Which Ig is most common in late stages/secondary response of fighting non-self antigen

A

IgG

55
Q

How do antibodies protect against infection?

A

Specific binding -> NEUTRALISATION of toxins, immobilise microbes, form complexes

Enhance innate mechanisms -> activate complement, bind Fc receptors - OPSONISATION (enhancing Phagocytosis), release of inflammatory mediators by mast cells

56
Q

What are mechanisms of Humoral Immunity?

A

Neutralisation
Lysis (complement)
Phagocytosis (PMN, macrophage)

57
Q

Define allergy

A

Abnormal Response to Harmless Foreign Material (Immunological)

58
Q

Define atopy

A

tendency to develop allergies

59
Q

Define Anaphylaxis

A

An acute allergic reaction to an antigen to which the body has become hypersensitive

60
Q

Define Autoimmunity

A

A disease in which the body produces antibodies that attack its own tissues, leading to a pathological process.

Medicine Phase 2a (22 decks)

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