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Immunology > L1. Introduction > Flashcards

L1. Introduction Flashcards

1
Q

What are 3 functions the immune system must carry out?

A
  1. Provide defence or IMMUNITY against INFECTION
  2. Distinguish between SELF and NON-SELF, reacts against NON-SELF
  3. May also recognise DANGER signals caused by damage to cells and tissues (e.g. stroke, cancer)
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2
Q

What are 3 contrasting characteristics of a)Innate b)Adaptive immune systems?

A

a) Innate
>Broad specificity
>Not affected by prior contact
>Immediate/ rapid response (mins-hours)

b) Adaptive
>Highly specific
>Enhanced by prior contact
>Slow response (days-weeks)

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3
Q

What are the 4 groups of defences of the innate immune system (give 2 examples of each)?

A
  1. Barriers (physical e.g. skin, chemical)
  2. Soluble proteins (complement, interferons etc.)
  3. Local and systemic responses (inflammation-local, fever-systemic)
  4. Leukocytes (phagocytes, NK cells)
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4
Q

What are the 2 arms of the adaptive immune system?

A
  1. Humoral immunity
  2. Cell-mediated immunity
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5
Q

What do all immune cells derive from and where are they found?

A

Haematopoietic stem cells, found in bone marrow.

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6
Q

What are the 2 types of immune cell types and what falls under them?

A
  1. Myeloid: (all innate)
    >Monoblasts (monocyte making either macrophage or dendritic cell)
    >Neutrophil, eosinophil, basophil
  2. Lymphocyte: (all adaptive other than NK)
    >B cell
    >T cell
    »Natural killer cell

(NK cells are apart ofinnate immunity but are lymphocyte cells)

(All are types of leukocytes)

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7
Q

What receptors do adaptive immune cells present?

A

B (antibody) or T cell receptors

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8
Q

What receptors do innate immune cells present and what do they recognise?

A

Pattern Recognition Receptors (PRRs) recognise Microbial Associated Molecular Patterns (MAMPS or PAMPS)

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9
Q

What are 3 characteristics of MAMPS?

A
  1. Unique to microbes
  2. Conserved (hard for microbe to have different isoforms)
  3. Essential for microbe survival
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10
Q

What are the 2 characteristics of a PRR?

A

Limited number of PRRs in body but have very broad specificity.

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11
Q

Why don’t PRRs evolve quickly and what is the effect of this?

A

Genes are passed down germline (inherited) so evolve slowly, means pathogens evolve quicker so need adaptive immune system to cope.

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12
Q

What do NK cells recognise?

A

NK cells are lymphocyte cells that recognise altered “self” (due to infection)

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13
Q

Do different leukocytes express different PRRs?

A

Generally PRRs expressed by all leukocytes of a particular type(same phagocytes of a particular type will have same PRR receptors).

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14
Q

Why do B and T cells have receptors specific for just 1 antigen?

A

So when in contact with that antigen can undergo clonal selection/ expansion meaning more antibodies specific to this will be secreted.

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15
Q

What is the main difference between PRRs and B/T receptors?

A

B/T receptors are highly specific while PRRs are broad.

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16
Q

Why is the immune system described as a double edged sword?

A

As it needs to maximise host defence whilst minimizing damage to host tissues

17
Q

Describe clonal selection in 3 steps

A
  1. Millions of B cells each with a different antibody produced in the body at random.
  2. Naïve B cell recognises the antigen at draining lymph node.
  3. Undergo clonal selection, where the B cell parent divides and differentiates to produce plasma cells which secrete soluble antibodies.
18
Q

What is one issue with B and T receptors being produced at random?

A

Lymphocytes that recognise “self” are produced and need to be deleted early in development

19
Q

What is an advantage and a disadvantage of the innate immune system?

A
  1. Good at distinguishing self to non-self as MAMPs aren’t found on self-cells (MAMPs are unique to microbes)
  2. Potential for collateral damage to self (immunopathology), might produce substances which damage host cells as doesn’t have a really specific response.
20
Q

What is an advantage and a disadvantage of the adaptive immune system?

A
  1. Cannot reliably distinguish between self/non-self or between harmful/innocuous material, B and T cells may develop with receptors recognising own tissues (must be killed)
  2. Targets immune response specifically towards infection, sparing uninfected tissues.
21
Q

How do the innate and adaptive immune system interact and why?

A

> Innate immune system activates and directs adaptive responses.
Adaptive immune system can control and focus innate immunity (so doesn’t cause too much collateral damage)
Together maximise host defence whilst minimizing damage to host tissues (usually)

Due to the two branches evolving together

22
Q

Where do all Lymphoid cells develop?

A

Bone marrow (as contains haematopoietic stem cells)

23
Q

Where do a) B cells b) T cells mature?

A

a) Bone marrow

b) Thymus

(Both primary lymphoid tissue)

24
Q

Where does clonal selection/expansion occur and why?

A

> Secondary lymphoid tissue e.g. lymph nodes in neck and tonsils.

> Where naive lymphocytes are stimulated by antigen triggering clonal selection and expansion.

25
Q

What is a naive lymphocyte?

A

A T or B cell that has a receptor on their surface but has not interacted with an antigen so has not undergone clonal selection yet.

26
Q

Describe in 6 steps how an immune response is triggered if the infection is far from a draining lymph node

A
  1. Bacteria get into skin
  2. Dendritic cells and macrophages (phagocyte) recognise pathogen and present its antigen.
  3. These cells travel through draining lymph nodes to the secondary lymphoid tissue
  4. Naïve B and T cells (have antigen receptors), if come into contact with the presented antigen complimentary to their receptor causes activation (clonal expansion)
    a. Usually T cell has to be activated first (thymus dependent)
    b. B cells can also be activated if their receptors recognize free antigens or antigens presented by APCs, but they often require “help” from activated T cells (especially in response to protein antigens, termed “T cell-dependent activation”).
  5. T cell divides and differentiates, releasing cytokines mediating B cell division and differentiation (clonal expansion).
  6. Specific soluble monoclonal antibodies will be secreted from plasma cells into lymphatic vessels to travel to the infected site.

Immunology (20 decks)

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