Immune tolerance in pregnancy
Immune tolerance in pregnancy or maternal immune tolerance is the
.Mechanisms
Placental mechanisms
The placenta functions as an immunological barrier between the mother and the fetus, creating an immunologically privileged site. For this purpose, it uses several mechanisms:
- It secretes
- Also, there is the presence of small lymphocytic suppressor cells in the fetus that inhibit maternal cytotoxic T cells by inhibiting the response to interleukin 2.[2]
- The placental
- It forms a immunoevasive action was the initial normal behavior of the viral protein, in order to avail for the virus to spread to other cells by simply merging them with the infected one. It is believed that the ancestors of modern viviparous mammals evolved after an infection by this virus, enabling the fetus to better resist the immune system of the mother.[6]
Still, the placenta does allow maternal
Other mechanisms
Still, the placental barrier is not the sole means to evade the immune system, as foreign fetal cells also persist in the maternal circulation, on the other side of the placental barrier.[9]
The placenta does not block maternal IgG antibodies, which thereby may pass through the human placenta, providing immune protection to the fetus against infectious diseases.
One model for the induction of tolerance during the very early stages of pregnancy is the
Regulatory T cells also likely play a role.[11]
Also, a shift from cell-mediated immunity toward humoral immunity is believed to occur.[12]
Insufficient tolerance
Many cases of
- Rhesus D antigen on their baby's red blood cells. It occurs if the mother is Rh negative and the baby is Rh positive, and a small amount of Rh positive blood from any previous pregnancy has entered the mother's circulation to make their produce IgG antibodies against the D antigen (Anti-D). Maternal IgG is able to pass through the placenta into the fetus and if the level of it is sufficient, it will cause destruction of D positive fetal red blood cells, leading to development of the anti-Rh type of hemolytic disease of the fetus and newborn(HDFN). Generally, HDFN becomes worse with each additional Rh incompatible pregnancy.
- One cause of pre-eclampsia is an abnormal immune response towards the placenta. There is substantial evidence for exposure to partner's semen as prevention for pre-eclampsia, largely due to the absorption of several immune modulating factors present in seminal fluid.[13][14]
Pregnancies resulting from
Infertility and miscarriage
Immunological responses could be the cause in many cases of infertility and
Antiphospholipid antibodies are targeted toward the
Antinuclear antibodies cause an inflammation in the uterus that does not allow it to be a suitable host for implantation of the embryo. Natural killer cells misinterpret the fetal cells as cancer cells and attack them. An individual that presents with reproductive autoimmune failure syndrome has unexplained infertility, endometriosis, and repetitive miscarriages due to elevated levels of antinuclear antibodies circulating.[16] Both the presence of antiphospholipids antibodies and antinuclear antibodies have toxic effects on the implantation of embryos. This does not apply to anti-thyroid antibodies. Elevated levels do not have a toxic effect, but they are indicative of a risk of miscarriage. Elevated anti-thyroid antibodies act as a marker for females who have T-lymphocyte dysfunction because these levels indicate T cells that are secreting high levels of cytokines that induce inflammation in the uterine wall.[16]
Still, there is currently no drug that has evidence of preventing miscarriage by inhibition of maternal immune responses; aspirin has no effect in this case.[17]
Increased infectious susceptibility
The increased immune tolerance is believed to be a major contributing factor to an increased susceptibility and severity of infections in pregnancy.
Interspecific pregnancy
If the mechanisms of rejection-immunity of the fetus could be understood, it might lead to
References
- PMID 22992082.
- ^ S2CID 22815679.
- ^ "Placenta 'fools body's defences'". BBC News. 2007-11-10.
- ^ ISBN 978-0-7216-0004-8Published: September 2003
- S2CID 4367889.
- ^ Luis P. Villarreal (Sep 2004). "Can Viruses Make Us Human?" (PDF). Proceedings of the American Philosophical Society. 148 (3): 314. Archived from the original (PDF) on 2005-03-02.
- ^ Magnetic immunodiagnostic method for the demonstration of antibody/antigen complexes especially of blood groups Archived 2012-02-29 at the Wayback Machine Yves Barbreau, Olivier Boulet, Arnaud Boulet, Alexis Delanoe, Laurence Fauconnier, Fabien Herbert, Jean-Marc Pelosin, Laurent Soufflet. October 2009
- ^ MSD manuals > Perinatal Anemia Last full review/revision Oct 2020
- PMID 18384774.
- ^ S2CID 22626737.
- S2CID 33530468.
- ^ Jamieson DJ, Theiler RN, Rasmussen SA. Emerging infections and pregnancy. Emerg Infect Dis. 2006 Nov. Available from https://www.cdc.gov/ncidod/EID/vol12no11/06-0152.htm
- ^ Robertson, Sarah. "Research Goals --> Role of seminal fluid signalling in the female reproductive tract". Archived from the original on 2012-03-29.
- PMID 12896827.
- ^ PMID 20543201.
- ^ ISBN 978-1-58829-270-4
- PMID 20335572.
- ^ PMID 24897084.
- ^ Darwin's children LeVay, Simon. (1997, October 14). from The Free Library. (1997). Retrieved March 06, 2009