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Peds > Immuno > Flashcards

Immuno Flashcards

1
Q

TQ

-Acquired through placental IgG transport, breast feeding IGA

A

Passive + natural vaccination

active=acquired through recovery from infx

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2
Q

-Acquired through IV injection of anti-serum

A

Passive + artificial vaccination

active=immunization w/ vaccines

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3
Q

-Do not PREVENT infx, rather reduce severity of dz
»Th2 response
-Only rabies and hepatitis are therapeutic
-Primes immune response vs pathogen so that when you encounter it, you can fight it quickly w/ Abs & memory cells

A

Vaccines

directed at Ag epitopes»adaptive immunity

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4
Q

What kind of vaccine is…

Oral polio, varicella; mumps, measles, rubella, bacillus Calmette-Guerin (BCG)?

A

Live attenuated

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5
Q

What kind of vaccine is…

Inactivated polio

A

Killed/inactivated

can be used anytime

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6
Q

What kind of vaccine is…

Diphtheria toxoid, tetanus toxoid

A

Subunit

only some Ags

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7
Q

What kind of vaccine is…

Hep B

A

Recombinant subunit

Ags are recombinant

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8
Q

What kind of vaccine is…

Haemophilus influenzae type b, Streptococcus pneumoniae

A

Conjugate (polysaccharides-protein)

Streptococcus pneumoniae can also be given in polyvalent form (large # of Ags)

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9
Q

Passive immunization:
Ab from other species may cause systemic anaphylaxis (IgG)…otherwise known as what?
OR
May induce type III hypersensitivity with activation of complement in the tissues

A

serum sickness

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10
Q

Active immunization:
IM inactivated & live attenuated influenza vaccine & yellow fever vaccine are grown in chicken eggs…What does this pose a risk for?

A

allergic rxn if egg allergy

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11
Q
  • Infant immunity is not competent»infx

- Incr morbidity in neonates due to what?

A
  • Bacteria: group B streptococci & E. coli
  • Viruses: HSV, CMV, VZV, RSV (decr Th1)
  • Fungi: Candida
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12
Q

Is cell-mediated immunity transferred from mother to fetus?

A

NO, humoral is!

Infants rely on their own T cells to fight pathogens and respond to vaccination

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13
Q

TQ

Neonates have delayed IL-2 producing DC and therefore have impaired…

A

Th1 responses

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14
Q

How does cell mediated immunity work?
Th1 initiated when DC or Mφ eat pathogen»
IL-12 stim NK cells incr Th1 effector cells»???

A

IFN-γ»
Activates Mφ» pro-inflam cytokines IL-1β, TNF-α, IL-12.

(IFN-γ also promotes pathogen killing by macrophages)

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15
Q

TQ
Vaccination in newborn…low T cell response*

What are some examples?

High response to BCG though!

A
  • (HBVac) or oral poliovirus (OPV) vaccines»Th1 type responses that are lower than those seen in adults
  • Diminished delayed-type hypersensitivity (DTH) skin test reactions to Ags such as candida and tetanus toxoid
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16
Q

Abs against bacteria are directed against what?

A

cell wall Ags

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17
Q

What is the principal mechanism of defense against TI polysaccharide-rich Ags of encapsulated bacteria?

A

Humoral immunity

18
Q

What is the major protective immune response against extracellular bacteria?

A

Humoral immunity

Blocks infx, eliminate microbes, neutralize toxins, phagocytosis, complement activation

19
Q

TQ

Why were conjugate vaccines made?

A

To overcome the poor response to polysaccharide Ags by complexing polysaccharide Ags to immunogenic proteins, thus converting them into “T cell-dependent” Ag.

20
Q

IgA, IgM, IgD, and IgE do NOT cross the placenta. If elevated IgM or IgA are seen in cord blood, what does this suggest?

A

Intrauterine infx

21
Q

Which Ig rises rapidly 1 mo after birth as a response to the massive antigenic stimulation present in new environment

A

IgM

22
Q

TQ

Why is their a higher frequency of gram-negative infxs in newborns?

A

IgM isn’t effective as Ab produced later…doesn’t provide sufficient heat-stable opsonins

23
Q

TQ

Which infants have low opsonic activity for all types of organisms?

A

Premature infants (receive less maternal IgG)

24
Q

-Many bacterial polysaccharides of encapsulated bacteria are TI Ags.

What is the major mechanism of host defense against infx against encap bacteria?

A

Humoral immunity

25
Q

Transient hygogammaglobulinemia of infancy…most of the Igs are from mom’s IgG, but are higher/lower than moms (baby + mom). Premature infants have lower IgG.

A

higher

26
Q

TQ

Full-term neonates produce Ab to TD protein Ags such as tetnus and….

A
  • diphtheria toxoids
  • hepatitis B surface Ag
  • OPV
27
Q

TQ
Responses to TI Ags (polysaccharide) are severely blunted until approximately 18 to 24 months of age. What are some examples?

A

Capsular polysaccharides of:

  • H. influenzae type b
  • Group B streptococci
28
Q

TQ

Why were conjugate vaccines made?

A

Overcome the poor response to polysaccharide Ags by complexing polysaccharide Ags to immunogenic proteins, thus converting them into “T cell-dependent” Ag.

29
Q
  • Memory cells are generated in germinal centers for T-dep protein Ags
  • Memory cells are 1 of 4 types of B-cells. What are the 3 others?
A
  • Antibody secreting cells
  • Isotype switching cells
  • Affinity maturation cells
30
Q
  • TD Ags (proteins) and TI Ags (nonproteins) induce Ab responses with different characteristics.
  • The differences largely reflect the influence of Th cells in the responses to protein Ags. What are some differences?
A

TD-Ag–>isotype switching, affinity maturation, and memory B cells

TI-Ag–>low switching, no affinity maturation, no memory B cells

31
Q

-Many non-protein Ags (polysacc and lipids) stimulate Ab w/o Th cells

What are these Ags cells called?

Abs to these Ags are of low affinity and consist mainly of IgM, with limited isotype switching.

A

Thymus independent (TI)

32
Q

Most TI Ags are multivalent=composed of many identical Ag epitopes. Why is this impt?

A

Maximal cross-linking of the BCR complex on specific B cells»
Activation without T cell help!!

33
Q

TQ

Why is an asplenic pt at incr risk for encapsulated bacterial infx ?

A

Spleen has marginal zone B-1 cells (non-circ mature B cells) that are impt in Ab responses to TI antigens, mainly polysaccharides…produce IgM

34
Q

How are TI Ags (polysaccharides, glycolipids, and nucleic acids) processed?

A

Activate complement system by the alternative pathway»generating C3d»binds Ag»recognized by CR2 on B cell.

35
Q

-Some TI non-protein Ags can induce Ig isotypes other than IgM

Ex: pneumococcal capsular polysaccharide induces which Ab?

A

IgG2

36
Q
  • TI Ags contribute to their generaton
  • In circulation of normal individuals and produced w/o exposure to pathogens
  • low-affinity anti-carb Abs, produced by peritoneal B-cells (GI bacteria) and MZ B-cells (spleen)
A

Natural Ab

37
Q

TQ
-Effective vaccines must induce both affinity maturation & memory B cell formation (only happens if vaccine activates Th cells)
-How then do you design vaccines for capsular polysacc which cannot stim T cells?
What are these vaccines called ?

A

Conjugate vaccines

  • polysacch linked to foreign protein=hapten-carrier conjugate
  • Induces high-affinity Abs and memory cells

notes:
T cell=specific for carrier protein
B cell=polysacch specific

38
Q

How does the newborn’s immune sys cope w/ the surge of proinflam signals towards commensal bacteria at birth?

A

D71+ erythroid cells in neonatal human cord blood»immunosuppression via arginase-2

allows infants to adapt!

39
Q

TQ

What is arginase-2

A

Enzyme that impairs innate immune responses, including prod of Th1-promoting TNF-a

40
Q

TQ

What challenges the idea that the suscept of neonates to infx is due to immune-cell-intrinsic defects?

A
  • Decr in CD71+ cells w/ postnatal develop»loss of immunosupp
  • CD71+ cells quench excessive inflam induced by abrupt colonization w/ commensal microorgan after birth
41
Q

Necrotizing enterocolitis in premature babies may occur due to what?

A

-Over-rxn to influx of bacteria since immunosuppressive CD71+ cells haven’t developed

Limits Th1 cytokines produced by microbes

42
Q

TQ
From an eco pt of view, humans are a superorganisms, a communal collective of human + microbial cells working as one
-we should tail tx to both human and microbes

ex?

A

Fecal microbiota transplant

Peds (7 decks)

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