Which substance , on introduction into human body forms antibodies

Options

A. antigen
B. antibody
C. histamine
D. both A and B

Answer

**Step-by-Step Text Solution:**

1. **Understanding the Question**: The question asks which substance, when introduced into the human body, leads to the formation of antibodies.

2. **Defining Antigens**: An antigen is a foreign substance that triggers an immune response in the body. It is recognized by the immune system, which then produces antibodies specifically designed to bind to that antigen.

3. **Identifying Antibodies**: Antibodies, also known as immunoglobulins, are proteins produced by the immune system in response to antigens. They help identify and neutralize pathogens like bacteria and viruses.

4. **Analyzing the Options**:
- **Option A: Antigen**: This is the correct answer because antigens are the substances that induce the immune response and lead to the production of antibodies.
- **Option B: Antibody**: This is incorrect because antibodies are the result of the immune response, not the substance that induces it.
- **Option C: Histamine**: This is also incorrect as histamine is a chemical involved in allergic reactions and does not lead to the formation of antibodies.
- **Option D: Both A and B**: This is incorrect because only option A (antigen) is correct.

5. **Conclusion**: The substance that, when introduced into the human body, forms antibodies is the antigen.

**Final Answer**: Antigen

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