Read the given statements and select the incorrect one.

Options

A. An exaggerated immune response on exposure to pollen, dust, etc., in some individuals is due to release of histamine and serotonin from mast cells.
B. Immunodeficiency diseases are due to failure of immune system to distinguish between self and nonself cells.
C. During HIV injection, RNA genome of virus replicates to form viral DNA which gives incorporated into host cell's DNA.
D. Cancer cells resist induction of cell death and promotes tumour development.

Answer

To solve the question of identifying the incorrect statement among the given options, we will analyze each statement step by step.

### Step-by-Step Solution:

1. **Statement Analysis**:
- **Statement 1**: "An exaggerated immune response on exposure to pollen, dust etc. in some individuals is due to the release of histamine and serotonin from the mast cell."
- This statement describes hypersensitivity reactions, which are indeed caused by the release of histamine and serotonin from mast cells. This statement is **correct**.

2. **Statement 2**: "Immunodeficiency diseases are due to failure of the immune system to distinguish between self and non-self cells."
- This statement is misleading. Immunodeficiency diseases are characterized by a weakened immune system, which fails to protect the body from infections. The failure to distinguish between self and non-self cells is characteristic of autoimmune diseases, not immunodeficiency diseases. Therefore, this statement is **incorrect**.

3. **Statement 3**: "During HIV infection, the RNA genome of the virus replicates to form viral DNA which gets incorporated into host cell DNA."
- This statement accurately describes the process of HIV infection, where the viral RNA is reverse transcribed into DNA and then integrated into the host cell's DNA. This statement is **correct**.

4. **Statement 4**: "Cancer cells resist induction of cell death and promote tumor growth."
- This statement is true as cancer cells often evade apoptosis (programmed cell death), allowing them to proliferate uncontrollably. This statement is **correct**.

5. **Conclusion**:
- After analyzing all the statements, the only incorrect statement is **Statement 2**: "Immunodeficiency diseases are due to failure of the immune system to distinguish between self and non-self cells."

### Final Answer:
The incorrect statement is: **Immunodeficiency diseases are due to failure of the immune system to distinguish between self and non-self cells.**

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