What is the term for the ability of a pathogen to alter its surface antigens to evade host recognition?

• A. Antigenic variation
• B. Antibody diversification
• C. Immune evasion
• D. Antigen processing

Answer: (A)

Antigenic variation is the ability of a pathogen to alter its surface antigens to evade host recognition. By changing the proteins that the immune system uses to identify the invader, the pathogen can avoid being neutralized by existing antibodies and T-cell responses, allowing persistent infection or reinfection as the immune system continually encounters new variants. This mechanism is what underlies many cases of immune escape in viruses like influenza (which mutates surface proteins) and invaluable examples in parasites and bacteria that switch coats or surface structures.

Antibody diversification refers to the host's process of generating a wide array of antibodies, not to the pathogen changing itself. Immune evasion is the broad idea of avoiding immune detection, which includes antigenic variation but is not the specific mechanism. Antigen processing describes how immune cells break down and present antigens, not how pathogens alter their own surfaces.