**Core Concept**
Chemotherapy-induced agranulocytopenia is a life-threatening condition characterized by a severe reduction in neutrophil count due to chemotherapy agents that target rapidly dividing cells, including bone marrow cells. This results in an increased susceptibility to infections.

**Why the Correct Answer is Right**
The treatment of choice for chemotherapy-induced agranulocytopenia is granulocyte-colony stimulating factor (G-CSF), which stimulates the bone marrow to produce more neutrophils. G-CSF works by binding to its receptor on the surface of hematopoietic cells, triggering a signaling cascade that leads to the release of mature neutrophils into the circulation. This increases the neutrophil count and reduces the risk of infections.

**Why Each Wrong Option is Incorrect**

* **Option A:** This option is incorrect because antibiotics are not effective in treating agranulocytopenia, as they do not address the underlying cause of the low neutrophil count.
* **Option B:** This option is incorrect because corticosteroids, while useful in some cases of neutropenia, are not the first-line treatment for chemotherapy-induced agranulocytopenia.
* **Option C:** This option is incorrect because blood transfusions are not effective in treating agranulocytopenia, as they do not increase the production of new neutrophils.

**Clinical Pearl / High-Yield Fact**
It is essential to recognize that chemotherapy-induced agranulocytopenia is a medical emergency requiring prompt treatment with G-CSF to prevent life-threatening infections. G-CSF should be initiated as soon as possible after the diagnosis of agranulocytopenia is made.

**Correct Answer: D. G-CSF**