Immunology Of Pregnancy

Question 1

Rh factor

Answer 1

“Rhesus factor”

• a subset of antigens found on RBCs
• 85% of population is Rh+

is relevant in pregnancy since if a mother is Rh- and the first fetus is Rh+, the mother will develop antibodies to the Rh+ antigens (which can kill the 2nd fetus if its Rh+

Question 2

Hemolytic disease of a newborn

“Immune hydrops fetalis or HDFN”

Answer 2

A Rh- mother develops antibodies against the Rh+ fetus
- the first fetus is fine (since the antibodies are developing) but the second Rh+ fetus = hemolytic anemia and death usually)

• prevention = RhoGAM shots = Anti-D antibody coats the Rh antigen before the mother can start making her own (coats the fetal blood cells to prevent hemolytic anemia)*
• can also give fetal blood transfusions through umbilical cord if its too late from RhoGAM

Question 3

Ways that the mother is exposed to fetal blood

Answer 3

Delivery of the baby

Injury to the stomach during pregnancy

Aminocentesis

Early pregnancy complications

Question 4

Neonatal Fc receptors (FcRn)

Answer 4

Are soluble receptors athe maternal-placental interface (syncytiotrophoblasts) that bind the Fc region of maternal IgG.
- purpose is to keep maternal IgG inside the fetus to protect the fetus

Other ways are

• transport the IgG over placental tissue via transcytosis
• releases bound IgG into fetal blood circulation

Question 5

What is the dominant TH subset used in each trimester?

Answer 5

1st trimester
- TH1 = inflammation

2nd trimester
- TH2 = growth

3rd trimester
- TH1 = inflammation

Question 6

What are the ways the placenta acts as a”barrier and immune privileged” zone

Answer 6

Placental mechanical barrier
- prevents movement of immune cells into developing fetus (NOT all though)

Immune suppression during pregnancy occurs

• theory suggests that autoimmune diseases regress during pregnancy but come back after
• however pregnant females are no more or less susceptible to infections than non pregnant females

MHC class 1 is missing from trophoblasts (making it harder to mount an inflammatory response on placental tissues) 
- instead expresses HLA-G on trophoblasts 

Local and systemic cytokine shifts from TH1 and TH2 cytokine profile

• during TH1 = more susceptible for disease states
• TH2 = anti-inflammatory

Checkpoint proteins are expressed at the placental barrier
- the purpose of these is to induce “positive” effects on T-reg cells (Turns up Tregs which in turn turns down the general immune response at the placental interface)

Question 7

What immune cells surround the trophoblast

Answer 7

Tregs = systemic expansion during pregnancy occurs (believed that HLA-G stimulates Tregs)

NK cells (70% and most common)
- dont show cytotoxic activity against the trophoblast (HLA-C/G is the reason)

Macrophages (25%)
- are M2 macrophages

Dendritic cells (2%) 
- important for implantation and local cytokine involvement

Question 8

Indole amine-2,3-deoxygenase (IDO)

Answer 8

Is an enzyme involved in tryptophan catabolism
- one effect is to activate Treg cells

if you knock out the enzyme in pregnant females = spontaneous abortion believed to be due to autoimmunity = therefore this protects the fetus!!