Progenitors formed in bone marrow but differentiating elsewhere are

Options

A. Pre-NK cells
B. Pre-erythroblasts
C. Pre-T cells
D. Myeloblasts

Answer

To answer the question "Progenitors formed in bone marrow but differentiating elsewhere are," we will analyze the options provided and determine the correct answer step by step.

### Step-by-Step Solution:

1. **Understanding Progenitors**: Progenitors are precursor cells that give rise to specific types of cells. In the context of this question, we are looking for progenitor cells that originate in the bone marrow.

2. **Identifying the Options**:
- **Option 1: Pre-NK cells**: These are natural killer cells, which are primarily derived from the bone marrow but do not specifically differentiate elsewhere.
- **Option 2: Pre-erythroblast**: These are precursors to red blood cells (erythrocytes) and they both originate and differentiate in the bone marrow.
- **Option 3: Pre-T cells**: These are progenitors of T lymphocytes that are formed in the bone marrow but migrate to the thymus for differentiation and maturation.
- **Option 4: Myeloblast**: These are precursors to granulocytes and also originate and differentiate in the bone marrow.

3. **Analyzing Pre-T Cells**: Pre-T cells are specifically formed in the bone marrow and then migrate to the thymus, where they undergo further differentiation into mature T cells. This is a crucial point, as it aligns with the question's requirement of progenitors formed in the bone marrow but differentiating elsewhere.

4. **Conclusion**: Based on the analysis, the only option that fits the criteria of being a progenitor formed in the bone marrow but differentiating elsewhere is **Option 3: Pre-T cells**.

### Final Answer:
**Option 3: Pre-T cells**

---