The antigen present in pathogen is

Options

A. A specific protein involved in metabolism
B. Polysaccharide synthesised by it in the host
C. A specific protein or polysaccharide present on its coat
D. Any of the two A or B

Answer

**Step-by-Step Solution:**

1. **Understanding Antigens**: Antigens are substances that can provoke an immune response in the body. They are typically found on the surface of pathogens such as bacteria, viruses, and fungi.

2. **Types of Antigens**: The antigens present on pathogens can be specific proteins or polysaccharide molecules. These molecules are recognized by the immune system as foreign invaders.

3. **Recognition by the Immune System**: When a pathogen enters the body, the immune system does not recognize the entire pathogen but instead identifies the specific proteins or polysaccharides on its surface. This recognition is crucial for the immune response.

4. **Activation of the Immune Response**: Upon recognizing these antigens, the immune system gets activated. This leads to the sensitization of immune cells, which prepare to combat the pathogen.

5. **Antibody Formation**: The presence of antigens stimulates the formation of antibodies. Antibodies are specialized proteins produced by the immune system to neutralize or destroy the antigens.

6. **Conclusion**: Therefore, the antigens present in pathogens are primarily specific proteins or polysaccharides found on their surface. The correct answer to the question is that these antigens are the protein or polysaccharide coat of the pathogen.

**Final Answer**: The antigen present in the pathogen is a specific protein or polysaccharide molecule on its surface.

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