Child acquires antibody against ABO antigen at which age
## **Core Concept**
The ABO blood group system is a critical aspect of transfusion medicine and involves the presence or absence of specific antigens on the surface of red blood cells. These antigens can trigger an immune response if introduced into a host who lacks them, leading to the production of antibodies. Infants are initially protected against ABO incompatibility reactions due to the placentally transferred maternal antibodies.
## **Why the Correct Answer is Right**
At birth, infants have IgG antibodies against ABO blood groups that are not their own, which they acquired from their mother through the placenta. However, these maternal antibodies typically disappear from the infant's circulation by around 6 months of age. The infant starts producing their own antibodies against ABO antigens they do not possess after this period. By around 6 months of age, infants begin to produce their own antibodies in response to exposure to environmental antigens.
## **Why Each Wrong Option is Incorrect**
- **Option A:** *This option is incorrect because it suggests the child acquires antibodies at birth, which is partially true but not exactly what the question seems to be aiming for; the focus is on when the child starts producing their own antibodies.*
- **Option B:** *This option suggests the age of 2 years, which is too late considering the typical timeline for the disappearance of maternal antibodies and the onset of self-production of antibodies.*
- **Option D:** *This option suggests the age of 10 years, which is far beyond the age by which infants typically start producing their own antibodies against ABO blood group antigens.*
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that newborns have passive immunity from maternal IgG antibodies, which can cause ABO incompatibility issues. By around 6 months, infants start to produce their own antibodies, making this a critical period for understanding transfusion medicine and potential hemolytic disease of the newborn.
## **Correct Answer:** . 6 months