T-lymphocytes are

Options

A. Formed in thymus
B. Formed in bone marrow and preprocessed in thymus
C. Formed in thymus and preprocessed in bone marrow
D. Formed and preprocessed in bone marrow

Answer

**Step-by-Step Solution:**

1. **Understanding T-Lymphocytes**: T-lymphocytes, also known as T-cells, are a type of white blood cell that plays a crucial role in the immune system, particularly in cell-mediated immunity (CMI).

2. **Formation of T-Lymphocytes**: T-lymphocytes are initially formed in the bone marrow, which is a primary lymphoid organ.

3. **Maturation Process**: After their formation in the bone marrow, T-lymphocytes migrate to the thymus, which is another primary lymphoid organ, where they undergo maturation. This process is essential for them to become fully functional immune cells.

4. **Evaluating the Options**:
- Option 1: Formed in thymus - Incorrect, as they are formed in bone marrow.
- Option 2: Formed in bone marrow and processed in thymus - Correct, as they are formed in bone marrow and mature in thymus.
- Option 3: Formed in thymus and processed in bone marrow - Incorrect, as they do not form in the thymus.
- Option 4: Formed and processed in bone marrow - Incorrect, as they require the thymus for maturation.

5. **Conclusion**: The correct answer is option 2: "formed in bone marrow and processed in thymus."