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Why mother with Rh- sensetize not sensetize to the fist fetus with Rh plus but sensetize to the second one?
When Rh negative mother carries Rh positive fetus, mother's immune system will not react because most of the time , during the first pregnancy ,fetomaternal blood will not mix. This will happen at the time of parturition and when mother's immune system detects Rh + , it starts producing antibodies and for this it takes at least 3 week and this will have memory. So in her second pregnancy if in case fetomaternal blood are encountered, mothers immune system start destroying the blood cells of the fetus. This case is known as ErythroBlastosis Foetalis or Hemolytic Disease in new born (HDN)
What is the placenta barrier?
The placenta is an organ that connects the developing fetus to the uterine wall. The placenta supplies the fetus with oxygen and food, and allows fetal waste to be disposed via the maternal kidneys. The placenta develops from the same sperm and egg cells that form the fetus, and functions as a fetomaternal organ with two components, the fetal part (Chorion frondosum), and the maternal part (Decidua basalis).
What is the basic principle of the antigen-antibody reaction?
-the principle of antigen-antibody reaction is a process of the immune system in which immunoglobulin-coated B cells recognize a specific antigen and stimulate antibody production. T cells also play an essential role in the reaction. An antigen-antibody reaction begins with the binding of antigens to antibodies to form antigen-antibody complexes. These complexes may render toxic antigens harmless (neutralization), agglutinize antigens on the surface of microorganisms, or activate the complement system by exposing the complement binding sites on antibodies. Certain complement protein molecules immediately bind to these sites and trigger the activity of the other complement protein molecules, which cause antigen-bearing cells to lyse. Antigen-antibody reactions may start immediately with antigen contact or as much as 48 hours later. They normally produce immunity but may also be responsible for allergy, autoimmunity, and fetomaternal hematologic incompatibility. In the immediate allergic response, the antigen-antibody reaction activates certain enzymes and causes an imbalance between those enzymes and their inhibitors
How does Rhogam prevent erythroblastosis fetalis?
If an Rh-negative woman gives birth to an Rh-positive baby, she is given an injection of Rhogam within 72 hours of the birth. This immunoglobulin destroys any fetal blood cells in her bloodstream before her immune system can react to them. In cases where this precaution is not taken, antibodies are created, and future pregnancies may be complicated. Because antibody production does not usually begin in a previously unsensitized mother until after delivery, erythroblastosis in subsequent children can be prevented by giving the mother an injection of Rhogam within 72 hours of delivery. The preparation must be given after each pregnancy-whether it ends in delivery,The anti-Rh antibodies from the preparation destroy fetal RBCs in the mother's blood before they can sensitize the maternal immune system. If a massive fetomaternal hemorrhagehas occurred, additional injections of the preparation may be necessary. This treatment has a failure rate of about 1-2 percent, apparently due to the mother's sensitization during pregnancy rather than at delivery. Therefore, all mothers who have Rh-negative blood and no apparent sensitization (as indicated by antibody titer) should be treated with a standard 300g dose of Rh(D) immune globulin (Rhogam) at about 28 weeks of gestation. The exogenous antibodies in the mother's circulation are gradually destroyed over the next three to six months, and the mother remains unsensitized. Rhogam should also be given after any episode of bleeding and after delivery should be as nontraumatic as possible. The placenta should not be removed manually to avoid squeezing fetal cells into the maternal circulation. A newborn born with erythroblastosis should be attended to immediately by a pediatricianwho is prepared to perform an exchange-transfusionat once if required.By NITIN BAYALM.Sc. Molecular Biology & BiotechnologyTEZPUR CENTRAL UNIVERSITY, ASSAm
