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Embryology Immune System > 305 > Flashcards

305 Flashcards

1
Q

Why is the preterm infant considered a “compromised host”?

A

immaturity of the immune system, decreased levels of IgG and disruption of skin barriers

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2
Q

What organisms is the infant at risk of being colonized with from the maternal genital tract?

A

lactobacillus, E.choli, protective anaerobes, GBS and chlamydia

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3
Q

The prenatal GI tract is considered to be what?

A

sterile

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4
Q

Initial colonization of the neonate occurs where on the body?

A

neonatal skin, umbilical cord, genitals, eyes, throat and nares

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5
Q

GIT colonization occurs in what two stages?

A

1) at birth through contact with organism

2) through diet

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6
Q

How does breast milk promote a protective GIT environment?

A

maintains an acid environment, thereby limiting the growth of acid sensitive organisms, promotes the growth of lactobacillus and bifidobacterium and is protective against G+ and G- organisms

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7
Q

What sort of environment do formula fed infants have in their GIT?

A

formula promotes a buffer in the GIT, therefore it is a more alkaline environment, less protective

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8
Q

Why are probiotics given to the neonate?

A

It encourages the colonization with desirable flora (lactobacillus and bifidibacterium)

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9
Q

What are the affects of probiotics?

A

dec the risk for NEC, dec emesis events, inc gastric emptying time, inc number of stools, dec crying spells; no a/w inc nosocomial infx events

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10
Q

How is PMN fx limited in the neonate?

A

1) poor response to chemotaxic factors
2) impaired mobilizations (dec ability to leave vasculature)
3) decreased chemotaxis
4) decreased opsonization (r/t dec levels of immunoglobulins and complement comp)
5) decreased phagocytosis
6) decreased macrophage activity
7) low levels of natural killer cells
8) unable to inc neutrophil production

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11
Q

What are the most common cytokines?

A

Interleukin 1 and Interleukin 6

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12
Q

Why is the neonate unable to inc neutrophil production?

A

less bone marrow reserve, fewer neutrophils in the reserve pool. neutrophils that are produced are immature and with impaired fx

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13
Q

What is the net result of an impaired neonatal immune system?

A

the infant is unable to localize infx leading to generalized sepatcemia

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14
Q

How does stress affect the immune system?

A

1) dec bactriocidal activity (both G+ and G-)
2) dec phagosytosis
3) dec ability to localize infx

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15
Q

Why are there changes in cellular metabolism and decreased phagocytosis r/t stressed and SGA infants?

A

due to decreased oxygen consumption, O2 free radicals all of which compromise bacteriocdial activity

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16
Q

What is the only immunoglobulin to cross the placenta?

A

IgG

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17
Q

When does IgG begin to cross to the neonate?

A

Beginning in the 3rd mo GA and increasing until term; greatest transfer is in the last trimester

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18
Q

What are the most important IgGs?

A

IgG1 and IgG3; non specific responders via opsonization

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19
Q

When is IgA present in the fetus?

A

30wk GA; does NOT cross placenta; introduced after birth via breast milk

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20
Q

When is secretory IgA present in the neonate and where?

A

by 2-3 wk of age postnatally; present in intestinal mucosa, tear and saliva; provides local immunity

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21
Q

Which immunoglobulins are directly responsible for antibodies against the most common organisms causing neonatal sepsis?

A

IgG and IgA

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22
Q

When is IgE produced and what is its function?

A

does NOT cross placenta, production begins at 12 weeks and provides protection against allergens

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23
Q

When is IgG produced and what is its function?

A

productions begins at 12 weeks and provides protection against G- organisms and viruses

24
Q

IgM is predominately secreted by what?

A

B lympocytes

25
Q

What is the crucial role played by IgM?

A

fetus can produce immunoglobulin in response to TORCH infections after 19-20 wk GA; protection against blood borne pathogens

26
Q

Compared to adults, what is the specificity of IgM?

A

less specificity

27
Q

What is the major immunoglobulin synthesized in the first month of postnatal life?

A

IgM

28
Q

Where are T lymphocytes produced?

A

in the thymus

29
Q

What is the role of the T lymphocytes?

A

to recognize foreign antigens by interacting with a major histocompatibility complex antigen

30
Q

Why are MHC important to T cells?

A

It is the only way that t cells can recognize infected cells is through MHC identification

31
Q

What does the release of lymphokines achieve?

A

recruits macrophage, lymphocytes and phagocytes and inhibits viral replication

32
Q

What is the function of helper T cells?

A

to release lymphokines and recruit antibodies

33
Q

What is cell mediated immunity comprised of?

A

T cells, natural killer cells and B cells

34
Q

What are the types of T cells?

A

helper T cells and suppressor cells

35
Q

What is the function of the suppressor cells?

A

turn off antibody reactions

36
Q

What is the function of the cytotoxic (natural killer) cells?

A

they are lethal to tissues invaded by viruses and destroy cancer cells and other foreign invaders

37
Q

What is the function of the lymphokines?

A

activate helper T cells and are endogenous pyrogens

38
Q

Why are neonates at increased risk for infections?

A

1) dec fx ability of T lymphocytes
2) immature T lymphocyte receptors
3) lymphokine production reduced
4) suppressor cell activity is dormant
5) dec cytotoxic activity
6) dec number of T cells

39
Q

When do T cells appear in the neonate?

A

do NOT cross the placenta; immunity can take 4-6 weeks postnatally to develop

40
Q

What is the function of the complement system?

A

1) back up to immunoglobulins
2) attach antibody “tail” after contact with antigen
3) proteins connect in a cascade and attach antigen destroying it
4) assists with inflammation and opsonization

41
Q

What is the state of the complement system of the neonate?

A

few protein components (in term infant, levels are 50-75% that of an adult; 28wk GA infant they are 10-30%)

42
Q

What is the result of an impaired complement system?

A

decreased opsonization, decreased chemotatic activity and decreased cell lysis

43
Q

What are common G+ cocci in neonates?

A

Strep A, B, D pneumoniae, staph, staph a, staph epi

44
Q

What are common G- cocci in neonates?

A

Neisseria, Neisseria meningitidis, Neisseria gonorrhoeae

45
Q

What are common G+ rods in neonates?

A

Listeria, diphtheriae, clostridium, c.diff, c. tetani, corynebacterium

46
Q

What are common G- rods in neonates?

A

enterobacteriaceae, E.coli, Klebsiella, Shigella, Proteus, Salmonella, H influenza, Psesudomonas

47
Q

What is the antibiotic of choice for staph aureus?

A

cephalosporin+ methicillin/ vanc/ clindamycin

48
Q

What is the antibiotic of choice for strep a & B?

A

Penicillin G or amp

49
Q

What is the antibiotic of choice for pseudomonas?

A

gent + ticarcillin

50
Q

By 1 year of age, total immunoglobulin levels are what precent of adult values?

A

60%

51
Q

What are the levels of IgG postnatally?

A

significant inc in first 6 months, adult levels by 5-6 years

52
Q

What are the levels of IgA postnatally?

A

20% of adult levels at 1 year of age, complete levels by adolesence

53
Q

What are the levels of IgM postnatally?

A

50% of adult levels by 6 months, 75-80% adult levels by 1 year

54
Q

What are the levels of complement postnatally?

A

increased to adult levels by 6-12 months

55
Q

When is T cell function mature?

A

by 3-6 mos

56
Q

When does an infant’s risk of infection decrease?

A

after 2-3 months of age

57
Q

What is the level of function of a neutrophil postnatally?

A

chemotaxic ability is decreased until 2 years of age, monocyte chemotaxis decreased until 6-12mo

Embryology Immune System (1 decks)

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