Immunity in the Newborn

Question 1

in utero, what immune organ develops first?

Answer 1

the thymus

Question 2

after the thymus, what 2 immune organs develop in utero?

Answer 2

bone marrow and then secondary organs

Question 3

is lymphocyte development usually done by birth? is there a species exception?

Answer 3

usually not, but development is done in chickens at hatch

Question 4

describe the concept of intestinal microflora and their role in the immune system

Answer 4

there are commensal microbes interacting with epithelial immune cells in the intestines

Question 5

what are intestinal microflora essential for?

Answer 5

functional development of the immune system (innate immunity especially)

Question 6

when do microbes get into newborns?

Answer 6

immediately after birth

Question 7

describe the newborn innate immune response (3)

Answer 7

1. is the majority of the newborn immune response
2. newborns have antimicrobial molecules, or innate cellular components that are fully functional at birth
3. newborns are deficient in complement proteins

Question 8

when does an immune response become enhanced with complement proteins?

Answer 8

about two weeks after birth

Question 9

describe the newborn adaptive immune response

Answer 9

1. response is antibody skewed

2. requires maternal assistance

Question 10

describe how maternal assistance helps the adaptive immune response of newborns in mammals

Answer 10

there is passive transfer of antibodies via colostrum

Question 11

why is the adaptive immune response in newborns antibody skewed?

Answer 11

lymphocyte developent not done yet, and IFN-gamma may harm the placenta so it is not around yet either

Question 12

what does prenatal passive antibody transfer depend on?

Answer 12

placental structure

Question 13

describe prenatal passive transfer of antibodies in humans, including placenta type

Answer 13

have hemocorial placenta, so there is direct contact of fetus with maternal blood and so there is transfer of IgG

Question 14

describe prenatal passive transfer of antibodies in dogs and cats, including placenta type

Answer 14

endothelialchorial placenta type, so there is some contact with maternal capillaries, therefore there is transfer of SOME IgG, but only 10% of what is needed

Question 15

describe prenatal transfer of antibodies in ruminants, horses, and pigs, including placenta type

Answer 15

prevention of IgG transfer due to epitheliochorial placenta type, therefore these newborns are entirely reliant on colostrum for passive transfer of maternal antibodies

Question 16

describe how prenatal transfer of antibodies occurs in chickens

Answer 16

IgY (immunoglobulin yolk) is transfered in the egg yolk, so chickens are covered at hatch

Question 17

what do antibodies in colostrum represent?

Answer 17

what the mother was exposed to in her own environment; includes vaccines and contacted antigens

Question 18

in what two antibodies is colostrum rich?

Answer 18

IgG and IgA

Question 19

what percents of antibody content of colostrum is composed of IgG?

Answer 19

65-90%

Question 20

where do the IgG and IgA in colostrum come from?

Answer 20

the bloodstream

Question 21

what 3 things in colostrum rich in?

Answer 21

1. IgG and IgA
2. cytokines
3. lymphocytes, neutrophils, and macrophages

Question 22

what four cytokines are in high concentrations in colostrum?

Answer 22

1. IL-1
2. Il-6
3. TNF-alpha
4. IFN-gamma

Question 23

what happens to the IgG from colostrum once the newborn consumes it?

Answer 23

it is absorbed and enters the bloodstream

Question 24

what happens to the IgA from colostrum once the newborn consumes it? why?

Answer 24

it remains in the intestinal tract to prevent antigen entry through the tract; if something does enter, then IgG takes care of it

Question 25

why is absorption of colostrum so high immediately after birth? (3)

Answer 25

1. protease activity in the GI tract is low, so antibodies stay whole in the tract until they are absorbed
2. to enhance this effect, colostrum also contains protease inhibitors
3. Fc receptors on the intestinal epithelium allow for whole body absorption, and they are at their highest concentrations immediately after birth

Question 26

how do Fc receptors work to allow for absorption of whole antibodies?

Answer 26

1. Fc portion of antibody binds Fc receptors that allow for absorption of intact antibodies
2. antibodies are then transferred to the bloodstream

Question 27

does the concentration of Fc receptors in intestinal epithelium (that allow for absorption of whole antibodies) reamin higher after birth?

Answer 27

no; they are at their highest concentrations immediately after birth and then rapidly decline within 24 hours

Question 28

when do local IgA responses appear in newborns?

Answer 28

early on

Question 29

what do maternal anitbodies do in newborns in regards to the newborn’s own immune response

Answer 29

they inhibit systemic B lymphocyte responses, newborn’s body doesn’t have to do the work for a while

Question 30

what is the tricky thing about vaccinating newborns?

Answer 30

there is a critical window where mom’s anitbodies will be low enough to stimulate an adaptive response by the newborn itself but not so high that the baby response will be smothered by mom’s antibodies, but also want baby to be proected and not die when you vaccinate

Question 31

what do you do the help with the trickiness and critical window of vaccinating newborns around mom’s antibodies?

Answer 31

administer boosters to stimulate a more robust response with baby’s own immune system once mom’s antibodies die down