Which of the following is not typical of an immunogenic antigen?

• A. Viral protein.
• B. Foreign nucleic acid.
• C. Molecules not made by the host organism.
• D. Cytoplasmic proteins commonly found in host skin cells.

Answer: (D)

Verified step by step guidance

1. Understand the concept of an immunogenic antigen: An immunogenic antigen is a substance that can provoke an immune response in the body. Typically, these are foreign substances that the immune system recognizes as non-self.
2. Identify the characteristics of typical immunogenic antigens: They are usually foreign to the host, such as viral proteins or foreign nucleic acids, and are not naturally produced by the host organism.
3. Analyze the options given: Viral proteins and foreign nucleic acids are examples of substances that are foreign to the host and can trigger an immune response.
4. Consider the option 'Molecules not made by the host organism': This aligns with the definition of an immunogenic antigen, as these molecules are foreign and can provoke an immune response.
5. Evaluate the option 'Cytoplasmic proteins commonly found in host skin cells': These proteins are naturally occurring within the host's own cells and are not foreign, making them atypical as immunogenic antigens.