The human immunodeficiency virus (HIV) causes AIDS by :

Options

A. Depleting `CD_(4)^(+)` -T- helper lymphocytes
B. Increasing `CD_(4)^(+)`-T- helper lymphocytes
C. Depleting `CD_(8)^(+)` -T- helper lymphocytes
D. Depleting `CD_(4)^(+)`-T- helper erythrocytes

Answer

### Step-by-Step Solution:

1. **Understanding HIV and AIDS**:
- The human immunodeficiency virus (HIV) is the causative agent of Acquired Immunodeficiency Syndrome (AIDS). AIDS is characterized by a significant weakening of the immune system.

2. **Mechanism of HIV Infection**:
- HIV primarily targets immune cells, particularly T-helper cells (also known as CD4+ T cells). These cells are crucial for orchestrating the immune response.

3. **Entry into Immune Cells**:
- HIV enters the body and infects macrophages first, using them as a means to replicate. It then specifically targets T-helper cells.

4. **Destruction of T-helper Cells**:
- Once inside the T-helper cells, HIV replicates and eventually leads to the destruction of these cells. This depletion of T-helper cells is critical because they play a vital role in activating other immune cells, including B-cells that produce antibodies.

5. **Consequences of T-helper Cell Depletion**:
- The loss of T-helper cells results in a weakened immune response. This means that the body becomes less capable of fighting off infections and diseases, leading to the opportunistic infections that are characteristic of AIDS.

6. **Identifying the Correct Option**:
- Among the options provided, the correct answer is that HIV causes AIDS by depleting T-helper lymphocytes (CD4+ T cells). The other options regarding CD8+ T cells and erythrocytes are incorrect.

### Final Answer:
The human immunodeficiency virus (HIV) causes AIDS by depleting T-helper lymphocytes (CD4+ T cells), leading to a weakened immune response.

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