Q.76
Edema toxin of Bacillus anthracis
(A) . A zinc-dependent metalloprotease
(B) . Impairs ability of phagocytes to internalize bacteria
(C) . Induces a decrease in circulating lymphocyte population
(D) . Diminishes the neutrophil oxidative response to bacteria
Choose the correct answer from the options given below:
- Pathophysiology of Anthrax Toxins (Bacillus anthracis):
- Enzymatic Identity: Anthrax Edema Toxin is composed of Protective Antigen (PA) and Edema Factor (EF). EF is an intrinsic, calcium/calmodulin-dependent adenylate cyclase that dramatically elevates intracellular cAMP ($\gt 1,000$-fold), inducing massive tissue edema. Lethal Factor (LF), by contrast, is the zinc-dependent metalloprotease that cleaves MAP kinase kinases (MAPKKs) [Statement A is FALSE].
- Impairment of Phagocytosis: Markedly elevated cAMP levels disrupt cellular actin cytoskeletal dynamics, preventing macrophages and dendritic cells from phagocytosing and internalizing bacteria [Statement B is TRUE].
- Lymphocyte Depletion: EF suppresses T-cell and B-cell receptor-mediated activation and induces apoptosis, decreasing circulating lymphocyte numbers [Statement C is TRUE].
- Neutrophil Deactivation: Strongly impairs the generation of reactive oxygen species (oxidative burst) and migratory chemotaxis in neutrophils [Statement D is TRUE].
Correct option: (4) (B), (C) and (D) only.
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