Adaptive Immunity During Pregnancy
The cornerstone of the immune system is the recognition of "self" versus "non-self". Therefore, the mechanisms which protect the human fetus (which is considered "non-self") from attack by the immune system, are particularly interesting. Although no comprehensive explanation has emerged to explain this mysterious, and often repeated, lack of rejection, two classical reasons may explain how the fetus is tolerated. The first is that the fetus occupies a portion of the body protected by a non-immunological barrier, the uterus, which the immune system does not routinely patrol. The second is that the fetus itself may promote local immunosuppression in the mother, perhaps by a process of active nutrient depletion. A more modern explanation for this induction of tolerance is that specific glycoproteins expressed in the uterus during pregnancy suppress the uterine immune response (see eu-FEDS).
During pregnancy in viviparous mammals (all mammals except Monotremes), endogenous retroviruses (ERVs) are activated and produced in high quantities during the implantation of the embryo. They are currently known to possess immunosuppressive properties, suggesting a role in protecting the embryo from its mother's immune system. Also viral fusion proteins apparently cause the formation of the placental syncytium in order to limit the exchange of migratory cells between the developing embryo and the body of the mother (something an epithelium will not do sufficiently, as certain blood cells are specialized to be able to insert themselves between adjacent epithelial cells). The immunodepressive action was the initial normal behavior of the virus, similar to HIV, the fusion proteins were a way to spread the infection to other cells by simply merging them with the infected one (HIV does this too). It is believed that the ancestors of modern viviparous mammals evolved after an infection by this virus, enabling the fetus to survive the immune system of the mother.
The human genome project found several thousand ERVs classified into 24 families.
Read more about this topic: Adaptive Immune System
Famous quotes containing the words adaptive, immunity and/or pregnancy:
“The shift from the perception of the child as innocent to the perception of the child as competent has greatly increased the demands on contemporary children for maturity, for participating in competitive sports, for early academic achievement, and for protecting themselves against adults who might do them harm. While children might be able to cope with any one of those demands taken singly, taken together they often exceed children’s adaptive capacity.”
—David Elkind (20th century)
“Mistakes, scandals, and failures no longer signal catastrophe. The crucial thing is that they be made credible, and that the public be made aware of the efforts being expended in that direction. The “marketing” immunity of governments is similar to that of the major brands of washing powder.”
—Jean Baudrillard (b. 1929)
“The frequency of personal questions grows in direct proportion to your increasing girth. . . . No one would ask a man such a personally invasive question as “Is your wife having natural childbirth or is she planning to be knocked out?” But someone might ask that of you. No matter how much you wish for privacy, your pregnancy is a public event to which everyone feels invited.”
—Jean Marzollo (20th century)