Earliest immunoglobulin to be synthesized by foetus in response to infection: September 2010
**Core Concept**
The development of the fetal immune system is crucial for protecting the fetus from infections. Immunoglobulins, or antibodies, are key components of the immune response, providing protection against pathogens. During fetal development, the immune system begins to mature, allowing the fetus to respond to infections.
**Why the Correct Answer is Right**
The earliest immunoglobulin synthesized by the fetus in response to infection is IgM. This is because IgM is the first immunoglobulin to be produced by the fetus, and it is essential for providing immediate protection against infections. IgM is produced by the fetus's B cells, which are activated by the presence of pathogens. The production of IgM is crucial for the development of the fetus's immune system, and it plays a significant role in the prevention of infections during fetal development.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because IgG is the most abundant immunoglobulin in the fetus, but it is not the first to be synthesized in response to infection. IgG is primarily transferred from the mother to the fetus through the placenta.
* **Option B:** This option is incorrect because IgA is an important immunoglobulin for mucosal immunity, but it is not the first to be synthesized by the fetus in response to infection.
* **Option C:** This option is incorrect because IgE is primarily involved in allergic reactions and parasite immunity, but it is not the first immunoglobulin to be synthesized by the fetus in response to infection.
**Clinical Pearl / High-Yield Fact**
The production of IgM by the fetus is a critical step in the development of the immune system, and it provides immediate protection against infections. This process is essential for the prevention of infections during fetal development, and it highlights the importance of the immune system in protecting the fetus from harm.
**Correct Answer:** A. IgM.