Question

Suppose you have two A-B-type exotoxins, A-B and A’-B’. A-B binds specifically to all MHC-II+ cells and blocks vesicle trafficking. A’-B’ binds specifically to all MHC-I+ cells and stops protein synthesis.

A. What would a hybrid toxin, A’-B, do to fibroblast (skin) cells? Provide your rationale.

B. What would a hybrid toxin, A-B’, do to fibroblasts? Provide your rationale.

C. What would a hybrid toxin, A’-B, do to macrophages? Provide your rationale.

D. What would a hybrid toxin, A-B’, do to macrophages? Provide your rationale.

Answer 1

A.) A'-B toxin will bind specifically to all MHC-I + cells ( such as fibroblast) and will block vesicle trafficking , secretion of  extracellular matrix rich in collagens will get blocked.

B.) A-B' toxin will hardly bind to healthy fibroblast cells because Healthy fibroblast cells do not express class II MHC molecules but this toxin can bind to inflammed fibroblast cells, expressing class II MHC and stop protein synthesis.

C.) A'-B toxin will bind to macrophages and will block protein synthesis and various pro inflammatory molecules . Being professional APCs ,they express both class I and class II MHC molecules.

D.) A-B' toxin will bind to macrophages and block vesicle trafficking.