Prenatal and Neonatal Immunity Flashcards
primordial stem cell
- progenitor stem cell compartment
- responsible for providing the pre-thymic cells that seed the thymus
- 1st lymphoid organ to begin to develop, in utero, T cells are the first lymphocytes
to appear
what happens to the progenitor stem cell compartment early in prenatal development?
takes up residence in the fetal liver and then seeds bone marrow, then develop spleen and lymph nodes where IgM- bound B cells appear, followed by cell of innate immune system and complement proteins, last lymphoid tissues to develop are MALT ( peyer’s patch)
true or false: at parturition, neonates have an immunocompetent immune system that is immune protective
false, not immune protective
why is the thymus early in life large?
huge number of T cells are trafficking through the thymus to seed the secondary lymphoid tissues (i.e. spleen and lymph nodes)
what are the two ways maternal passive immunity can be conveyed?
in ovo or colostrum
the more closely the placental tissues are in contact with the maternal vascular tissues the easier it is for the maternal antibodies to cross the placental tissue, via a special _____ receptor, and gain access to the fetal circulation, in utero.
FcRn
which species do not get passive immunity via placenta
ruminants. horses, pigs
which species is discoid hemochorial placenta found in?
humans/primates, rodents (mice and rats)
discoid hemochorial placenta
the fetal placenta chorion has eroded through the maternal endothelium of the blood vessels
allowing it to be in direct contact with the maternal blood. This occurs because the maternal
endometrial epithelium, connective tissue and uterine endothelium are lost or absent. Mediated
via a FcRn receptor, maternal IgG can cross the placenta into the fetal circulation. Note, this is
the only isotype that can cross the placenta. So, with this type of placenta, maternal passive
immunity is primarily conveyed in utero provided the gestation time reaches full term. In
humans, maternal passive immunity (IgG) starts to be conveyed across the placenta within the 3-
4 month of gestation
zonary endotheliochorial placenta
common in dogs,
cats and elephants. Zonary implies that placenta exists as a tissue band (complete or incomplete)
around the fetus. With this type of placenta, the syncytial trophoblasts of the chorion are contact
with the maternal uterine blood vessels, but not in direct contact with the maternal blood. With
this type of placenta, the endometrial epithelium and connective tissue are eroded or lost, but the
uterine endothelium is retained. As a result, a limited amount of maternal IgG can cross the
placenta into fetal circulation, but not enough to convey adequate passive immunity. Thus, in
these species suckling from the mammary gland to obtain colostrum is also important.
cotyledonary epitheliochorial,
cows,
sheep, goats, llamas and alpacas. Cotyledonary describes a placenta that has multiple discrete
sites of uterine wall attachments called cotyledons. The maternal sites are called caruncles. With
this type of placenta, all 3 of the maternal layers are retained resulting in no maternal IgG
crossing the placenta, in utero. Thus, in these species, suckling from the mammary gland is the
only way in which maternal passive immunity is conveyed and only occurs post parturition
diffuse epitheliochorial
horses and pigs.
Diffuse implies that practically the whole surface of the allantochorion functions as the placenta.
Since it is epitheliochorial in nature, similar to the placenta found in ruminants, all 3 of the
maternal layers are retained resulting in no maternal IgG crossing the placenta, in utero. Again,
as in the ruminants, suckling from the mammary gland is the only way in which maternal passive
immunity is conveyed and only occurs post parturition
colostrum
rich in lactoferrin, lysozyme, lactoperoxidase, α-lactalbumin, β-lactoglobulin, fat, growth factors
and of most important antibodies (IgG, IgA and IgM). After the colostrum is consumed during
the 1st suckling, it converts over to milk rich in IgA with some IgG, more so in veterinary
species
human colostrum content
concentrated amount
of proteins and other nutrients (i.e. fats, carbohydrates, minerals and vitamins
rich in IgA and
this continues as the mammary secretion changes to milk. The logical rationale for this is that the
maternal IgG is conveyed in utero during gestation. Thus, after a normal birth the infant should
have adequate levels of maternal passive immunity systemically and most of the maternal milk is
geared toward nutrient uptake and supporting healthy GI development. Although some maternal
IgG is conveyed prenatally in species with zonary endothelial placentas, it is not sufficient for
optimal maternal passive immunity. So, suckling colostrum is important for these species in
particular in those species that have multiple offspring (i.e. dogs and cats). Lastly, those species
with either cotyledonary or diffuse epitheliochorial placentas only acquire maternal passive
immunity via colostrum. Thus, suckling colostrum soon after birth is extremely important for
survival of the neonates. If these neonates don’t receive colostrum then they are characterized as
having Failure of Passive Transfer and usually require medical intervention.
positive breast feeding effects
Maternal milk provides signals to the gut and to the immune system to facilitate
immune response and memory. There is also sufficient documentation that breastfeeding appears
to decrease the incidence of immune-based disorders (i.e. allergies, ear infections and atopic
diseases). In humans, in is believed to also have an important impact on infant maternal bonding
