True statement regarding diphtheria is
**Core Concept**
Diphtheria is a bacterial infection caused by Corynebacterium diphtheriae, characterized by the production of a toxin that leads to localized and systemic complications. The toxin, diphtheria toxin, is a potent inhibitor of protein synthesis, causing cell death and tissue damage.
**Why the Correct Answer is Right**
The correct answer is related to the pathophysiology of diphtheria. Diphtheria toxin works by catalyzing the ADP-ribosylation of elongation factor-2 (EF-2), a crucial protein involved in protein synthesis. This modification prevents the translocation of the ribosome along the mRNA, leading to the accumulation of unfinished polypeptide chains and ultimately, cell death. The toxin is produced by the bacteria in response to environmental signals and is secreted into the surrounding tissue, where it causes damage.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the pathophysiology of diphtheria. While the toxin does cause cell death, it is not a result of an immune response.
**Option B:** This option is incorrect because it is not a characteristic of diphtheria toxin. The toxin is not a direct cause of inflammation.
**Option C:** This option is incorrect because it is not a true statement regarding diphtheria. The toxin is not produced in response to stress.
**Clinical Pearl / High-Yield Fact**
Diphtheria toxin is a classic example of a bacterial toxin that inhibits protein synthesis, leading to cell death. This mechanism of action is similar to that of other bacterial toxins, such as ricin and Pseudomonas aeruginosa exotoxin A.
**Correct Answer:** B.