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WEEK 4 SEM 4 > Development of the immune system > Flashcards

Development of the immune system Flashcards

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1
Q

Why is the immune system in children dampened compared to adults?

A
  • immunosuppressive environment of the womb

= womb was sterile
= baby didnt need active immune system

  • at birth baby is exposed to many antigens- having a reaction to all of them, would be harmful to baby
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2
Q

Why was the womb immunosuppressive?

A
  • so maternal immune system doesn’t reject antigens of foetus AND VICE VERSA
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3
Q

When the baby is born why are they vulnerable to pathogens?

A
  • dampened immune system

- not good response to vaccines when born

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4
Q

What is immunoessence in pneumonia?

A
  • common in first few months of life
  • common in elderly again
  • immune system changes with age
  • pneumococcal disease is an opportunistic infection
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5
Q

What are the 2 parts of the immune system?

A
  • non antigen specific

- antigen specific

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6
Q

What is the non- antigen specific immune system made up of?

A
  • barriers = skin/mucosal surfaces
  • cellular components = neutrophils, monocytes, macrophages NK cells= PHAGOCYTOSIS
  • soluble components = complements (opsonization) and cytokines (cell signalling)
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7
Q

Why do preterm babies have higher risk of infection?

A

bc thin skin

easy to penetrate barrier

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8
Q

How do monocytes, macrophages etc detect pathogens?

A

WBC have TLR which detect PAMP on bad guys

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9
Q

What is antigen specific immune system made up of?

A

B cells

T cells

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10
Q

What are B cells?

A
  • have antibodies on them
  • specific for antigen
  • millions of B cells with diff antibodies respond to diff antigens
  • can produce memory cells
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11
Q

What are the 2 types of T cells?

A
  • CD4+ T helper

- CD8+ cytotoxic cells

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12
Q

What are CD4+ T helper cells?

A
  • dendrites present antigens to these cells through their MHC
  • immature T helper cells get activated
  • help activate CD8+ T cytotoxic cells
  • also help antibody class switching in B cells
  • memory T helper cells produced
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13
Q

What are CD8+ cytotoxic cells?

A
  • cells infected by viruses and bacteria present antigens to these
  • leads to their activation
  • chemicals from T helper cells help mature the cytotoxic T cells which can then attack infected body cells
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14
Q

What is a primary lymphoid organ?

A
  • Thymus= in thorax, T cells develop

- Bone marrow= stem cells giving rise to blood cells (e.g. T and B lymphocytes)

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15
Q

What is a secondary lymphoid organ?

A
  • SPLEEN
    = filter blood
    = remove old damaged RBC
    = remove infec agents- use them to activate lymphocytes
  • LYMPH NODES
    = in subcut tissue
  • PEYERS PATCHES
    = in intestine
    = filter out dead cells
  • LYMPHATIC VESSELS
    = collect lymph fluid that has leaked out from blood into tissues
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16
Q

Why do people without a spleen have high infection rate and by what in particular?

A
  • high infection risk by encapsulated bacteria

e. g. pneumococcus and meningococus

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17
Q

What are the phases the development of the immune system can be divided into? MHSM

A
  • MESOBLASTIC
  • HEPATIC
  • SPLENIC
  • MYELOID
18
Q

What happens in the mesoblastic stage?

A

MESOBLASTIC:

  • 10 weeks
  • production of haematopoietic cells in the yolk sac
  • haematopoeitic cells = precursors for all the blood cells including lymphocytes (B and T cells)
19
Q

What happens in hepatic stage?

A
  • happens in liver
  • begin 6-8 weeks gestation
  • continue till shortly after birth
20
Q

What happens in the myeloid phase?

A
  • happens in bone marrow
  • 10-12 weeks gestation
  • by 20 weeks its a major blood cell forming site
21
Q

How do T cells develop?

A
  • develop in bone marrow
  • migrate to thymus
  • go through gene rearrangement and becomes T cells
22
Q

What happens in the thymus?

A
  • T cells undergo gene arrangement

- develop specificity

23
Q

What is the thymus and where is it derived from?

A
  • organ
  • derived from 3rd pharyngeal pouch
  • located in thorax
  • thymus has cortex and medulla
  • cortex has THYMOCYTES (which are T lymphocytes)
  • medulla has dendrites, macrophages, and the Hassall’s corpuscle (function unknown)
24
Q

How does the thymus develop?

A
  • 8 weeks gestation= thymus colonized by haematopoietic stem cells (precursors for blood cells like lymphocytes)
  • 20 weeks of gestation= thymus completely developed
  • 16-20 weeks gestation= T cells go from thymus to peripheral bodies
25
Q

How are Th1 lymphocytes produced?

A
  • Th1 lymphocytes are produced by exposure to IL12 and IL18

- secrete IFN gamma which activates macrophages to kill intracellular bacteria

26
Q

What secetes Th2?

A

IL4

  • activates macrophages
  • kills parasitic worms
27
Q

What produces Th17 and IL22?

A
  • exposure to IL6 and TGFB

- which attract neutrophils and induces antimicrobial peptide production

28
Q

What is Treg lymphocyte produced by?

A
  • exposure to retinoic acid and TGFB

- inhibit immune responses through IL10

29
Q

How do B cells develop?

A
  1. develop in bone marrow
  2. mature in bone marrow
  3. migrate to 2ndary organs
30
Q

What do B cells express?

A
  • immunoglobulins on cell surface membranes (antibodies) = specific to a certain antigen
  • many diff types of B cells= many diff types of Ig
  • done through gene rearrangement
31
Q

What happens when an immature B cell encounters an antigen?

A
  • once the immature B cell encounters an antigen which matches the Ig on top of it
  • matures
  • replicates
32
Q

Newborns are deficient in self-generated antibodies and are thus in an immunosuppressant state- How do you sort this out?

A
  • transplacental active transfer of maternal IgG antibody

= last trimester = active transport of IgG from mum to foetus
= IgG half life is a month

  • Secretory IgA in breast milk

= important to coat mucosal surfaces= prevent things like gastroenteritis

33
Q

When does the baby produce its own antibodies?

A

3 months

34
Q

How do babies develop antibodies (in what order?)

A
  1. IgG production increases slowly with IgG 1 and IgG 3 2. IgG 2 and IgG 4
  2. IgA reaches adult levels the latest
35
Q

At what week are cellular components of non antigen specific component of the immune system seen?

A

31 weeks gestation

36
Q

Granulocytes are high in numbers in newborns but less effective than adults. Why?

A
  • reduced motility (movement)
  • cannot cross the blood vessels’ endothelial layer
  • BUT their adherence and phagocytosis is similar to an adult
    HIGH GRANULOCYTE NUMBER BUT LOW SUPPLY
37
Q

Why are bacterial infections more likely in babies?

A
  • increased susceptibility to bacterial infections such as group B streptococcus
  • low qualitative and quantitative (less number low quality)
  • AB deficiency
  • complement protein deficient
  • less phagocytic cells at infection site
38
Q

Why are viral infections more likely?

A
  • antibody deficient
  • less NK cells
  • low cytokines
  • low macrophage activity
  • low T cell cytotoxicity
39
Q

How do we protect newborn infants?

A
  • give antibiotics/antivirals at any sign of infection
  • wash hands
  • encourage breastfeeding- IgA
  • give mother important vaccinations so antibodies are passed down to child
  • give infant vaccinations when required
40
Q

Why is breastmilk good in infants?

A

breast milk also contains:

  • macrophages, neutrophils and lymphocytes
  • complements which help with opsonization
  • lysozyme which attacks bacterial cell walls
  • lactoperoxidase which is an antistreptococcal agent
  • lactoferrin which inhibits growth of bacteria
41
Q

Why dont you give vaccinations to newborns?

A
  • maternal Ig come in the way

- poorly developed immune system when born

42
Q

Why do you give BCG vaccine at birth?

A
  • for Tb
  • elicits a cell mediated response
  • babies have stronger cellular response than a humoral response (antibody response)

WEEK 4 SEM 4 (6 decks)

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