Immunodeficiency in the host, caused by HIV is due to

Options

A. Depletion of helper T cells
B. Depletion of RBC
C. Increase of helper T cells
D. Depletion of platelets

Answer

### Step-by-Step Solution:

1. **Understanding HIV**: Human Immunodeficiency Virus (HIV) is a virus that specifically targets the immune system of the host, leading to immunodeficiency.

2. **Target Cells of HIV**: HIV primarily infects T helper cells, also known as CD4+ T cells. These cells are crucial for the immune response as they help activate other immune cells.

3. **Mechanism of Infection**: Once HIV enters the body, it binds to the CD4+ molecules on the surface of T helper cells. This binding allows the virus to enter the cells.

4. **Replication of HIV**: After entering the T helper cells, HIV replicates and produces more copies of the virus. This process eventually leads to the death of the infected T helper cells.

5. **Consequences of T Helper Cell Depletion**: As HIV continues to infect and kill T helper cells, the overall number of these cells decreases significantly. This depletion impairs the immune system's ability to respond to infections, leading to immunodeficiency.

6. **Conclusion**: Given the options provided, the correct answer to the question is **Option A: depletion of T helper cells**. This depletion is the primary reason for immunodeficiency in hosts infected with HIV.