The Human Immunodeficiency Virus causes AIDS by:

Options

A. Depleting `CD_4^(+)` T-helper lymphocytes
B. Increasing `CD_4^(+)` T-helper lymphocytes
C. Depleting `CD_4^(-)` T-helper lymphocytes
D. Increasing`CD_4^(-)` T-helper lymphocytes

Explanation

**Step-by-Step Solution:**

1. **Understanding HIV and AIDS**: The Human Immunodeficiency Virus (HIV) is the virus responsible for causing Acquired Immunodeficiency Syndrome (AIDS). It is crucial to understand the relationship between the two.

2. **Entry of HIV into the Body**: HIV enters the human body through various means, such as unprotected sexual contact, sharing needles, or from mother to child during childbirth or breastfeeding.

3. **Replication in Macrophages**: Once inside the body, HIV targets immune cells, particularly macrophages. It utilizes these cells as a "viral factory" to replicate itself.

4. **Infection of T-helper Cells**: After replicating in macrophages, the new viral particles are released and infect T-helper cells (also known as CD4+ T-cells). These cells are crucial for the immune response.

5. **Depletion of T-helper Cells**: HIV specifically depletes T-helper cells by binding to the CD4 receptor on their surface. This leads to a significant reduction in the number of these cells in the body.

6. **Impact on Immune Function**: T-helper cells play a vital role in signaling B-cells to produce antibodies against pathogens. With the depletion of T-helper cells, the immune system becomes weakened, leading to immunodeficiency.

7. **Conclusion**: The depletion of CD4+ T-helper lymphocytes by HIV is the primary mechanism through which the virus causes AIDS. This results in a compromised immune system, making the individual more susceptible to infections and diseases.

**Final Answer**: The Human Immunodeficiency Virus causes AIDS by depleting CD4+ T-helper lymphocytes, leading to a weakened immune system.

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