Fetal and Neonatal Immunity Flashcards
Immunity in the fetus
- 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
Antibodies provided by the mother
- 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
IgG transport from the blood into extracellular spaces
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
Transcytosis of IgA across eptihelia
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
There is a transient decrease in levels of _____ in the 1st year of life
IgG
- completely eradicated in the fetus by 9 months
- fetus only has IgM for a short period of time = vulnerability
What is the one natural situation that leads to production of anti-MHC antibodies?
Pregnancy
- paternal HLA isoforms that differ from mother’s HLA type have potential to stimulate an alloreactive immune response
____ is an immunologically privileged organ
Uterus
Transfer of disease by immune effectors
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
Hemolytic disease of the newborn
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
Thymus in calves develops around _____
41 days
Hemochorial placenta
Humans, primates
- IgG levels in infant are comparable to those of its mother (100% transfer)
Endotheliochorial
Dogs, cats
- 5-10% of IgG may be transferred
Syndesmochorial (ruminants) and epitheliochorial (horses, pigs)
Passage of Ig is totally prevented, newborns are entirely dependent on antibodies received thru colostrum
Mammalian placentation
Classified on basis of maternal layers retained in placenta
- more layers (epitheliochorial), the more restricted the movement of blood between mother and fetus
Ruminant vs non ruminant milk
Ruminant: mostly IgG, some IgA, little IgM
Nonruminant: Mostly IgA, some IgG, little IgM
6 weeks
Maternal antibodies are declining and calf antibodies are being formed
Maternal antibodies inhibit _____
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
Birth of a persistently infected calf
BVDV in early pregnancy –> cow and calf infected –> only dam becomes immune –> calf born persistently infected –> superinfection with second BVDV biotype = fatal mucosal disease
FcRn transports ____ and poly-ig-receptor transports ____
IgG; IgA
Babies born to mothers with ____ will not show disease symptoms
T cell-mediated autoimmune diseases
- lymphocytes cannot pass from maternal to fetal circulation
In hemolytic anemia, immune complexes of fetal RBCs coated with _____ prevent a primary B cell response from being made to the Rh antigen
IgG
