24- Fetal and Neonatal Immunity

Question 1

How is tolerance of the fetus by the dam achieved?

Answer 1

• Progesterone: high levels near trophoblast are immunosuppressive at fetal-maternal interface
• Increased complement regulatory proteins: block activation and thus complement-mediated cytolysis of fetal/placental tissues
• TH2 response dominates: humoral response, lowers chance for TH1 mediated cytolysis of fetal tissue
• High levels of Tregs

Question 2

How is maternal-fetal tolerance achieved by the fetus?

Answer 2

• fetal cells down regulate MHC I (presents a smaller amount of self antigens)
• Th2 cytokines are expressed
• inhibit T-cells

Question 3

What is the timing for developing an adaptive immune response?

Answer 3

Adaptive immune response requires a population of primary and secondary lymphoid organs in the 1st trimester. Adaptive response increases slowly after population of lymphoid organs (thymus develops first)

Question 4

Fetal innate response and developing adaptive response can be passivley supplemented by maternal antibodies. How so?

Answer 4

• either absorbed pre-natally through placenta or ingested post-natally through colostrum
• placental absorption depends on placental type with 3 basic types seen in domestic species

Question 5

What are the types of placentas seen in domestic animals?

Answer 5

1) Epitheliochorial: swine, horses- NO Ig across the placenta to fetus, must get Ig from colostrum
- syndesmochorial- ruminants, maternal epithelial modified/fused but not lost)

2) Endotheliochorial: dogs, cats- loss of 2 layers

3) Hemochorial: primates, rabbits, guinea pigs- loss of 3 layers

Question 6

T/F: Species that maintain the maternal endometrial lining within the placenta transfer antibodies to fetus

Answer 6

FALSE- these placental types DO NOT transfer antibodies to fetus

Question 7

Colostrum has a mix of which antibodies?

Answer 7

IgG and IgA
Some IgM may be present, but it is too large to be absorbed by intestinal epithelium but they can remain in mucosa to prevent bad things from being absorbed

Question 8

Which is the only antibody that can pass through the placenta?

Answer 8

IgG

Question 9

IgG predominates in which species’ milk?

Answer 9

Ruminants, all other species IgA predominates

Question 10

What are some potential negative aspects of passive immunity?

Answer 10

Maternal antibody may impair neonatal adaptive immune response- response to vaccination, usually why vaccination is delayed until transfer of humoral immunity declines and neonates immune system is more mature

Question 11

What happens if maternal antibodies passed to the neonate recognize the neonatal tissue as foreign?

Answer 11

In damn, fetus may have a foreign blood type, dams could have antibodies against that blood type. The fetus is protected in utero because of placental layers, but once the foal nurses colostrum, the antibodies from the dam will attack foal’s “foreign” RBCs

AKA neonatal isoerythrolysis

Question 12

What is the most common source of immunodeficiency?

Answer 12

Failure of passive transfer (FPT)