Immunodeficiency makes a person highly susceptible to infection. It is caused by

Options

A. lack of B cells
B. lack of T cells
C. lack of both B and T cells
D. Lymphoma cells and bone marrow cells

Answer

**Step-by-Step Solution:**

1. **Understanding Immunodeficiency**: Immunodeficiency refers to a state where the immune system's ability to fight infections is compromised or entirely absent. This makes individuals more vulnerable to infections that a healthy immune system would typically combat effectively.

2. **Identifying the Cause**: The question asks what causes immunodeficiency. The options provided are:
- Lack of B-cells
- Lack of T-cells
- Lack of both B and T-cells
- Lymphoma cells in the bone marrow

3. **Role of B-cells and T-cells**:
- **B-cells** are responsible for producing antibodies, which are crucial for identifying and neutralizing pathogens.
- **T-cells** play a vital role in cell-mediated immunity. They help activate B-cells and directly kill infected host cells.

4. **Evaluating the Options**:
- A lack of **B-cells** would impair antibody production, leading to increased susceptibility to infections.
- A lack of **T-cells** would hinder the activation of B-cells and the overall immune response.
- A lack of **both B and T-cells** would severely compromise the immune system, making the individual highly susceptible to infections.
- The presence of **lymphoma cells** in the bone marrow could indicate a type of cancer affecting the immune system but does not directly answer the question about immunodeficiency.

5. **Conclusion**: The most comprehensive cause of immunodeficiency is the lack of both B and T-cells, as both are essential for a functional immune response.

**Final Answer**: The correct option is the lack of both B and T-cells.

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