AIPGMEE 2016 Pathology MCQ

A 5-year-old child has a history of recurrent bacterial
infections, including pneumonia and otitis media. Analysis
of leukocytes collected from the peripheral blood shows a
deficiency in myeloperoxidase. A reduction in which of the
following processes is the most likely cause of this child’s increased
susceptibility to infections?
A Hydrogen peroxide (H2O2) elaboration
B Hydroxy-halide radical (HOCl–) formation
C Failure of migration resulting from complement
deficiency
D Phagocytic cell oxygen consumption
E Prostaglandin production

Answer - B Myeloperoxidase is present in the azurophilic granules
of neutrophils. It converts H2O2 into HOCl–, a powerful
oxidant and antimicrobial agent. Degranulation occurs
as phagolysosomes are formed with engulfed bacteria in
phagocytic vacuoles within the neutrophil cytoplasm. Oxygen
consumption with an oxidative or respiratory burst after
phagocytosis is aided by glucose oxidation and activation
of neutrophil NADPH oxidase, resulting in generation of
superoxide that is converted by spontaneous dismutation
to H2O2. In contrast, prostaglandin production depends on
a functioning cyclooxygenase pathway of arachidonic acid
metabolism.