Neonate Immunity Flashcards
What is ontogeny?
The development of an individual organism or anatomical or behavioral feature from the earliest stage to maturity
What is the first lymphoid organ to develop?
thymus
What is the difference between short and long gestation in regards to immune system development?
Short gestation = primary lymphoid organs develop after birth
Long gestation = full development of the immune system at birth
Why is the immune system still vulnerable at birth even when fully developed?
The immune system is naive for several reasons including the fact that they are not exposed to antigens in utero unless there was an infection.
What drives the development of a good immune response by neonates?
Antigen driven by environmental exposure
What is the average time for fetal thymus development?
About 40 days post-conception
How long is the gestation period for foals, calves, and pigs?
foals: 340 days
calf: 280 days
pigs: 115 days
Why are neonates vulnerable to infection?
Innate immunity suppressed by fetal cortisol released during birth results in suppressed phagocytic function.
Adaptive immunity is naive and dependent on exposure to antigens.
Neonatal immune responses are biased toward Th2 immune responses and suppress Th1 immune responses.
What is the advantage of Th1 immune suppression in neonates?
IFN-y (produced by Th1 response)
CTLs could recognize foreign MHC I expressed by the fetus
What is the disadvantage of Th1 immune suppression in neonates?
Increased susceptibility to intracellular bacteria
What is passive immunity?
The transfer of active humoral immunity in the form of ready-made antibodies, from one individual to another
What maternal antibody is transferred across placental tissues?
IgG
What animals have free transfer of IgG across the placenta?
rodents, primates
What animals have no transfer of IgG across the placenta?
ruminants, horses, donkeys, pigs
What maternal antibody is transferred to the chicken egg?
IgY
What animals have slight transfer of maternal IgG? What percentage is it?
dogs and cats
5-10%
What animal has a hemoendothelial placentation and how many tissue layers?
rodents; 1
What animal has a hemochorial placentation and how many tissue layers?
primates; 3
What animal has a endotheliochorial placentation and how many tissue layers?
dogs and cats; 4
What animal has a syndesmochorial placentation and how many tissue layers?
ruminants; 5
What animal has an epitheliochorial placentation and how many tissue layers?
horse, donkeys, and pigs; 6
How is a neonate protected while the immune system becomes fully competent?
passive transfer- antibody (and cells) provided by an external source
How is passive immunity acquired?
maternal antibody via colostrum or placenta
administration of plasma containing antibodies (can be an injection)
What would you recommend for horse/cattle breeders do before foaling/calving?
vaccination
When are peak serum immunoglobulin levels normally reached?
12 to 24 hours
When do foals and calves begin to produce antibodies and when are they detectable?
Immediately upon exposure to antigens after birth
Detectable within 1-2 weeks of life and reach protective levels by 2 months
What is colostrum?
Mammary gland secretions occur late in pregnancy due to estrogens and progesterone
What is the primary antibody in colostrum of most domestic species?
IgG (65-90%)
Small amounts of IgA and IgM
What is the primary antibody in colostrum in primates?
IgA
What is the difference in composition of milk and colostrum?
Majority of Ig in milk in produced by lymphoid tissue and not transferred from serum like colostrum.
What is the predominant antibody in milk?
Ruminants- IgG1
Non-ruminants- IgA
What provides protection from enteritis in neonates?
Milk Ig (IgA/IgG1)
What provides systemic immunity in neonates?
colostral IgG
What receptor does IgG bind to on the intestinal epithelial cells of neonates?
Fc receptor (FcRn)
How much colostrum do calves and foals ingest on average?
2 Liters
What is gut closure?
After 24 hours, a new layer of enterocytes form that prevent absorption because they lack FcRn
How long do maternal antibodies last?
up to 6 months and degrades over time
What causes failure of passive transfer? (FPT)
production failure
ingestion failure of colostrum
failure of GI absorption of maternal immunoglobulins
What tests can be used to determine adequate passive transfer?
total protein
salt precipitation
ELISA (SNAP test)
Radial immunodiffusion assay (RID)
Why is the TP test precise?
globulins = TP-albumins
What kind of test is RID?
Radial immunodiffusion assay done on agar
How does age affect treatment for FPT?
<15hrs give 2-3 liters of colostrum
> 15 hrs and <3 weeks give plasma infusion
> 3 weeks watch and give antibiotics
When do you recheck a foal after treating for FPT? What are you rechecking?
12-24 hours after tx
checking IgG levels
