Which of the following is a property of endotoxin?

• A. It is highly antigenic and induces strong antibody responses
• B. It is secreted actively by living bacteria
• C. It is found in Gram-positive bacteria cell walls
• D. It is a component of the outer membrane of Gram-negative bacteria

Answer: (D)

Verified step by step guidance

1. Understand what endotoxins are: Endotoxins are lipopolysaccharide (LPS) components found in the outer membrane of Gram-negative bacteria.
2. Recall that endotoxins are not secreted actively by bacteria; instead, they are released when the bacterial cell wall is disrupted or the bacteria die.
3. Recognize that endotoxins are generally less antigenic compared to exotoxins, meaning they do not induce strong antibody responses.
4. Note that endotoxins are not found in Gram-positive bacteria because these bacteria lack an outer membrane; instead, they have a thick peptidoglycan layer.
5. Conclude that the defining property of endotoxins is their presence as a structural component of the outer membrane of Gram-negative bacteria.