Fetal and Neonatal Immunity

Question 1

Immunity in the fetus

Answer 1

• immune system is fully formed at birth and all acquired responses are primary
• obtain immunoglobulins from mother by direct placental transfer or by ingestion of colostrum
• failure of passive transfer results in constant infections
• milk provides constant supply of IgA

Question 2

Antibodies provided by the mother

Answer 2

• IgG: selectively distributed in teh body and transported from maternal to fetal circulation by FcRn in the placenta
• IgA: predominates in secretions of mucosal epithelia and passed to fetus by transcytosis mediated by poly-ig-receptor

Question 3

IgG transport from the blood into extracellular spaces

Answer 3

Fluid-phase endocytosis of IgG from blood by endothelial cells of blood vessel –> acidic pH of endocytic vesicle causes the association of IgG with FcRn, protecting it from proteolysis –> basic pH of extracellular fluid on basolateral face of endothelial cell dissociates IgG from FcRn

Question 4

Transcytosis of IgA across eptihelia

Answer 4

Binding of IgA to receptor on basolateral face of epithelial cell –> receptor mediated endocytosis of IgA –> transport of IgA to apical face of epithelial cell –> receptor is cleaved, IgA is bound to mucus thru the secretory piece

Question 5

There is a transient decrease in levels of _____ in the 1st year of life

Answer 5

IgG

• completely eradicated in the fetus by 9 months
• fetus only has IgM for a short period of time = vulnerability

Question 6

What is the one natural situation that leads to production of anti-MHC antibodies?

Answer 6

Pregnancy

- paternal HLA isoforms that differ from mother’s HLA type have potential to stimulate an alloreactive immune response

Question 7

____ is an immunologically privileged organ

Answer 7

Uterus

Question 8

Transfer of disease by immune effectors

Answer 8

Mother with Graves disease makes anti-TSHR antibodies –> during pregnancy, antibodies cross the placenta into the fetus –> newborn infant also suffers from Graves’ –> plasmapheresis removes maternal anti-TSHR antibodies and cures infant

Question 9

Hemolytic disease of the newborn

Answer 9

Immune complex-mediated inhibition of naive B cells is used to prevent hemolytic anemia of the newborn
= passive immunization with anti-Rhesus IgG
- pregnant RhD women are infused with purified human RhD-specific abs during the 28th week of pregnancy = mothers immune system responds to primary RhD antigen in secondary exposure fashion

Question 10

Thymus in calves develops around _____

Answer 10

41 days

Question 11

Hemochorial placenta

Answer 11

Humans, primates

- IgG levels in infant are comparable to those of its mother (100% transfer)

Question 12

Endotheliochorial

Answer 12

Dogs, cats

- 5-10% of IgG may be transferred

Question 13

Syndesmochorial (ruminants) and epitheliochorial (horses, pigs)

Answer 13

Passage of Ig is totally prevented, newborns are entirely dependent on antibodies received thru colostrum

Question 14

Mammalian placentation

Answer 14

Classified on basis of maternal layers retained in placenta

- more layers (epitheliochorial), the more restricted the movement of blood between mother and fetus

Question 15

Ruminant vs non ruminant milk

Answer 15

Ruminant: mostly IgG, some IgA, little IgM

Nonruminant: Mostly IgA, some IgG, little IgM

Question 16

6 weeks

Answer 16

Maternal antibodies are declining and calf antibodies are being formed

Question 17

Maternal antibodies inhibit _____

Answer 17

Vaccination
- may bind to injected antigens and accelerate their clearance, or they may bind to critical epitopes and prevent activation of B cell and antibody production

Question 18

Birth of a persistently infected calf

Answer 18

BVDV in early pregnancy –> cow and calf infected –> only dam becomes immune –> calf born persistently infected –> superinfection with second BVDV biotype = fatal mucosal disease

Question 19

FcRn transports ____ and poly-ig-receptor transports ____

Answer 19

IgG; IgA

Question 20

Babies born to mothers with ____ will not show disease symptoms

Answer 20

T cell-mediated autoimmune diseases

- lymphocytes cannot pass from maternal to fetal circulation

Question 21

In hemolytic anemia, immune complexes of fetal RBCs coated with _____ prevent a primary B cell response from being made to the Rh antigen

Answer 21

IgG