Lecture 11- Immunity in the Fetus and Neonate Flashcards
Fetuses and newborn animals have _____ of disease problems
lots
What are the 5 characteristics of the fetal/newborn immune system?
- no memory
- Confronted with many antigens
- All responses are primary
- have genes to generate B and T cells but yet to know which to use
What 4 reasons explain why the fetal/newborn immune system does not work very well at first?
- Have to grow fast
- Have to be able to run away from dangers
- Cannot put their efforts only on the immune system
- Divert protein synthesis on many things
When does the development of the prenatal immune system begin?
Early in gestation in all mammals.
Fetal growth is accompanied by _______.
Development of specialized cells.
What is the relationship between shorter gestation and immune system development?
Shorter gestation = less developed immune system at birth.
Describe the development of the immune system at each trimester.
1st: little function, just developing
2nd: developing self tolerance
3rd: immune system has everything functional but not yet effective
What is the outcome of infection of the fetus during trimester 1 or 2?
Most likely death.
What diseases can fetuses become immunocompetent to while in utero?
Ab to bovine viral diarrhea virus infection by bovine fetuses.
What are the components of the development of the prenatal immune system?
- Presence of primordial thymus
- Differentiation of specific CD lines during gestation
- Development and differentiation of other WBC population during gestation
When does the presence of the primordial thymus occur in fetal lambs and calves?
27-30 days into gestation.
What can a persistently infected fetus result in?
Immunologic tolerance.
What are the 3 results of intrauterine infection?
- Normal fetus
- Death of fetus
- Persistently infected fetus
How do fetuses become infected?
Transplacental infection.
What does the outcome of a fetal infection depend on?
- Virulence and type of organism
- Dose of organism
- Age of fetus
What are the possible outcomes of a fetal infection?
- Death: abortion or stillborn
- Malformation, congenital abnormalities
- Successful immune response
What is seen in the calf with BVDD?
Emaciated persistently infected calf.
Are normal animal fetuses and neonates immunocompetent?
Yes.
What is susceptibility to an infection in normal fetuses/neonates due to?
Unprimed immune system.
Describe the components of the slowly developing immune system of mammals.
- Less complement at birth than adults
- CD4, CD8, and CTR gamma-delta less than peak level
When does the immune system mature in mammals?
When the animal approaches sexual maturity (5-6 months).
What compensates for the impaired PMN phagocytosis in neonate cattle?
Very high leukocytes and PMNs and very active monocytes with high bacteria uptake.
Describe a neonate’s response to an antigen.
Slow, weak, and easily overcome.
What are the components of passive transfer of immunity in neonates?
- Antibody
- Cells
- Cytokines
What does immaturity of the immune system in neonates lead to?
- Moderation of disease but not prevention
- No placental Ab transfer in food animals
What is the most important example of passive immunity in newborn food animals?
Colostrum.
What does natural passive immunity provide the neonate with?
Immediate short-term protection; delays its ability to mount an optimum active immune response to vaccines.
What are examples of immune transfer from mother to child?
- Transplacental
- Colostrum
- Milk
- Eggs
What are the 2 ways IgG can be transferred to the fetus?
Placental or through colostrum.
How is IgG transferred through the placenta?
IgG selectively transferred from plasma across the placenta to the fetus in utero.
How is IgG transferred through the colostrum?
IgG selectively transferred from plasma and concentrated in colostrum; IgG absorbed from colostrum through gut to neonate’s bloodstream within the first 24 hours of birth.
What is the predominant Ig in serum, colostrum, and ruminant milk?
IgG.
What is the predominant Ig in non-ruminant milk?
IgA.
Colostrum contributes to _____________ immunity while milk contributes to ______________ immunity.
systemic, intestinal.
How are Ig’s able to be absorbed rather than degraded in the neonatal GIT?
- Low proteolytic activity
- Trypsin inhibitors in colostrum
Describe the specialized gut epithelial cells in the newborn.
- Receptor mediated: FcR on gut epithelial cells and taken up by pinocytosis
- Non-selective pinocytosis of macromolecules
When is absorption of colostral antibody the highest?
First 6 hours.
When does absorption of colostral antibody stop?
By the first approx. 24 hours.
What happens when the absorption of colostrum stops?
Specialized epithelial cells replaced by normal epithelial cells; closure time is influenced by the amount of colostrum.
What is the transfer of maternal immunity influenced by?
Type of placentation; placenta are classified according to the number of layers that separate fetal circulation from the maternal circulation.
What are the 3 types of placenta?
- Epitheliochorial
- Endotheliochorial
- Hemochorial
What species have an epitheliochorial placenta?
Horse, cow, pig, sheep.
What species have an endotheliochorial placenta?
Dog and cat.
What species have a hemochorial placenta?
Man and rodents.
What are the layers that separate the maternal and fetal blood from mom to fetus?
Maternal epithelium, CT, endometrial epithelium, chorionic epithelium, CT, fetal endothelium.
What is transferred from mother to child via the placental route in humans and primates?
IgG high (IgM, IgD, and IgA).
What is transferred from mother to child via the placental route in dogs and cats?
5-10% IgG.
What is transferred from mother to child via the placental route in ruminants (syndesmochorial)?
No placental transfer of Ig (transfer through colostrum).
What are the characteristics of colostrum?
- Secretions of mammary gland just before and after parturition (replaced by milk after 48 hours)
- High levels of protein mostly from the circulation
- IgG and IgM prominent from circulation
- IgA mostly from local production
What is the prominent Ig in primates, pigs/horses, and ruminants?
Primates: IgA
Pigs/horses: IgA
Ruminant: IgG, 30%.
What does the lack of transplacental transfer of Ab’s in ruminant fetus lead to?
Neonatal agammaglobulinaemia.
What do ruminant neonates heavily depend on for immunity due to lack of transplacental transfer of Ab’s?
Colostral Ab’s and immune cells (B cells, CD8 cells, macrophages, and neutrophils) which are all functional after absorption.
What is the ideal time for absorption of colostral Ab’s?
First 6 hours after parturition.
What is the amount of colostral Igs absorbed and available to the newborn directly proportional to?
Their levels in the colostrum and the amount of colostrum consumed before gut closure.
What is the half-life of maternal antibodies in horses and cattle?
21 days.
What is the half-life of maternal antibodies in cats and dogs?
8-10 days.
What does the half-life of maternal antibodies influence?
Vaccination schedules.
What is failure of passive transfer?
Condition in which neonates do not acquire protective serum levels of maternal Ab’s; inadequate transfer of colostral Ab’s to the neonate.
What is the consequence of neonates with FPT?
Most likely to develop clinical infections of the intestines, lungs, or joints.
What are the common causes of FPT?
- Mother may produce insufficient amounts
- Premature birth
- Insufficient colostrum accumulation
- Excessive dripping
- Premature lactation
- Inadequate intake by neonate due to multiple births
- Poor mothering
- Mastitis
- Failure of intestinal absorption
- Timing of ingestion
What % of foals fail to absorb a good quantity of intestinal Ab’s?
25%.
What amount of intestinal absorption of Ab’s is expected?
800 mg/dl; if less than 400 mg/dl there is severe infection.
How do you prevent FPT in piglets?
Clipping of needle teeth.
How is FPT treated within the first 24 hours of birth?
- Oral colostrum (best)
- Oral serum/plasma
- Oral commercial colostrum substitute
How is FPT treated after the first 24 hours of birth?
- IV serum or plasma (20 mL/kg)
- IP or SC serum, plasma, or whole blood
- IV, IO, or SC commercial Ig
What is a colostrometer?
Measures Ig content of colostrum with a specific gravity of > 1.050.
What is the adequate level of maternal Ig’s in colostrum?
> or equal to 5000 mg/dl.
How do you diagnose FPT?
ZnSO4 turbidity test kit.
Maternal antibodies are absorbed in intestine maximum level in ____________ hours after birth.
12-24 hours.
How long does it take for the canine distemper AB to reach insignificant level in puppies?
10-12 weeks.
Describe the transfer of passive immunity in chicks.
- IgG from blood or absorbed into the bloodstream from the yolk
- IgA locally secreted in oviduct or ingested from albumin to protect the intestines.
How is IgG absorbed for passive immunity in chickens?
Transferred from the hen’s serum to the yolk; absorbed with the yolk and appears in the chick’s serum.
How are IgA and IgM absorbed for passive immunity in chickens?
- Found in albumin
- Embryo acquires IgA and IgM when it swallows amniotic fluid.
Where are Ig’s within the egg?
- IgA and IgM in the albumin
- IgG in the yolk.
What is the role of the ovary of the avian oviduct?
A series of individual ova that swell with yolk material; one mature ovum is released at ovulation.
What is the role of the infundibulum of the avian oviduct?
Engulfs the released ovum from the body cavity; also the site of fertilization of the ova by sperm.
What is the role of the magnum of the avian oviduct?
A thick albumin secreted around the yolk.
What is the role of the isthmus of the avian oviduct?
The inner and outer shell membranes are secreted.
What is the role of the uterus (shell gland) of the avian oviduct?
Watery fluid is added to the albumin (plumping) then egg shell is slowly deposited around the egg.
What is the role of the vagina of the avian oviduct?
Semen is stored in tubules and released at ovulation; the musculature controls the time of egg laying.
What is the role of the cloaca of the avian oviduct?
The vent through which the egg passes as it is laid.
