Fetal & Neonatal Immunity

Question 1

Describe the immune system development.

Answer 1

-thymus develops first then secondary lymphoid organs
-B cells made after spleen & lymph nodes
-cell mediated IR & antibody production = late fetal life
-TCR diversity = limited in fetus & neonate
>low cytokine

Question 2

Describe the IS & intrauterine infections.

Answer 2

-fetus less capable of mounting IR bc adaptive IS not fully functional
-mild/innaparent infections in mother can be severe/lethal in fetus
>bluetongue virus, infectious bovine rhinotracheitis, bovine viral diarrhea, toxoplasmosis
-resp to infection determined by state of immunological development of fetus

Question 3

Describe BVDV.

Answer 3

-preg cows infected w a noncytopathatic BVDV early in conception (120d) = give birth to calves tolerant to BVDV
-cows infected w noncytopathic BVDV between (120-200d) give birth to normal calves
-infection of preg cows w cytopathic BVDV in first 100d of conception = abortion, reabsorption, mummification fetus
-malformations in calves originating from mom infected w cytopathic BVDV between 100-150d from conception
-calves from mothers infected w cytopathic BVDV after 150d from conception may be born normal

Question 4

Describe IR on newborn mammals.

Answer 4

-birth: animals move from sterile environment to one w many pathogens
-capable of mounting innate & adaptive IR
>adaptive mech not fully functional
-adaptive immune = primary resp
>slow resp & low conc of antibodies
>innate IR critical for survival in first wks of life
newborn relies on passive immune transfer from mom

Question 5

Describe innate immunity on newborn mammals.

Answer 5

-several antimicrobial molecules
-TLR
-neutrophils
>deficient bactericidial activity
>cortisol
-serum deficient in C3 & complement components
>C3 in newborn pigs reaches adult levels by 14d by age
-macrophages present but immature
>capable of phagocytizing bacteria = less efficient at killing, until after 7-10d
-fewer NK cells
>resp more strongly to IL2 or IL15 = more cytotoxic

Question 6

Describe adaptive immunity on newborn mammals.

Answer 6

-resp predom Th2 based
-delayed development IL12 making DC1
-activities of IL4 & IL13 from DC2
-newborn foal unable to express IFNy
>placental damage
>6-12 mo reach adult level
-high lymphocyte counts than adults
>low CD8 count

Question 7

Describe immunity transfer: from mom to offspring.

Answer 7

dependent on type of placenta
-hemochorial = primates
>allows maternal IgG transfer (not IgM, IgA, IgE)
-endotheliochorial = dog & cat
>5-10% of IgG directly transferred from the mother to puppy/kitten
>mostly thru colostrum
-syndesmochorial = ruminants & epitheliochorial = horses & pigs
>no transplacental passage of Ig molecules
>transfer dependent on colostrum

Question 8

Describe colostrum absorption.

Answer 8

-low protease activity in digestive tract
-allow Ig to reach SI intact
-binding w FcRn receptor on intestinal epi cells
-taken up by intestinal epi cells & transferred to lacteals & intestinal capillaries
-reach bloodstream

Question 9

Describe intestinal permeability of colostrum absorption.

Answer 9

1. selectivity of intestinal permeability
   >horse/pig
   -absorb IgG & IgM; IgA in intestine
   >ruminants
   -no selectivity
2. duration of intestinal permeability
   -highest in first 6h (no longer than 24h)
   -no more expression of FcRn

Question 10

Describe passive transfer.

Answer 10

-absorption of IgG from colostrum required for gen of systemic immunity
-intake of IgA or IgG1 from milk required for protection against enteric disease

Question 11

Describe production failure of passive transfer.

Answer 11

production failure
-premature birth
-premature lactation
-individual variation
>28% of mares make low quality colostrum
>measure SG
>1.06-1.08 = 3000 to 8500 mg/dL of IgG
><3000 mg/dL = inadequate

Question 12

Describe ingestion failure of passive transfer.

Answer 12

-multiple births
>colostrum prod dont rise in proportion to # of newborns
-poor mothering
-weakness in newborn
-poor suckling drive
-physical problems

Question 13

Describe absorption failure of passive transfer.

Answer 13

-concern in foals
>good husbandry = 25% foals fail to absorb enough lg
>economic value
-similar prob w alpacas

Question 14

Describe diagnosing the failure of passive transfer.

Answer 14

-ideal: IgG >800 mg/dL
-failure of passive transfer - IgG <400mg/dL
>partial failure: IgG >400-<800mg mg/dL
-test after 18-24h after birth

Question 15

Describe the management of failure of passive transfer.

Answer 15

-75% of foals w 200-400 mg/dL of IgG stay healthy
-IgG conc <200 mg/dL = foals not nursed within 6h of birth & received colostrum w IgG of less than 1000 mg/dL = receive additional colostrum
-colostrum store frozen @-15 to -20c (1y)
-fresh colostrum from primiparous mares used
-foals older than 15h = IV plasma infusion