Chemical nature of antigens From a chemical standpoint, an antigen capable of eliciting an adaptive immune response may be composed of which type(s) of biomolecule?

Introduction / Context:
Antigens are substances recognized by the immune system, typically by antibodies or T-cell receptors after processing and presentation. Knowing the broad chemical classes that can be antigenic helps in vaccine design and diagnostic immunoassays.

Given Data / Assumptions:

• Antigens vary widely in size and complexity.
• They may be T-dependent (often proteins) or T-independent (often polysaccharides).
• Lipids and nucleic acids can also be antigenic when appropriately presented or complexed.

Concept / Approach:

Proteins are generally the most immunogenic due to size, complexity, and ease of processing/presentation. Polysaccharides can be strong antigens (e.g., bacterial capsules) though often elicit T-independent responses. Lipids may be recognized via CD1-restricted T cells or when conjugated to proteins (haptens). Nucleic acids can be antigenic when complexed with proteins or in autoimmune settings. Therefore, multiple chemical classes can serve as antigens.

Step-by-Step Solution:

Verification / Alternative check:

Clinical vaccines include protein toxoids and polysaccharide (or conjugate) antigens; glycolipids are recognized by NKT cells, confirming multiple classes can be antigenic.

Why Other Options Are Wrong:

• Restricting to any single class ignores diversity of antigens.
• “Nucleic acid only” is overly narrow and incorrect.

Common Pitfalls:

• Confusing antigenicity (binding) with immunogenicity (ability to induce a response); context, size, and carriers matter.

Final Answer:

Any of these