Respiratory (oxidative) burst
What it means
When a phagocyte engulfs a microbe, membrane NADPH oxidase reduces O₂ to superoxide (O₂•⁻) — a sharp rise in oxygen consumption (the 'burst'). Superoxide is dismutated to H₂O₂; myeloperoxidase then converts it to hypochlorous acid (HOCl, 'bleach') → potent oxygen-DEPENDENT microbicidal killing inside the phagolysosome.
Worked example
Defective NADPH oxidase = chronic granulomatous disease — recurrent catalase-positive infections (Staph, Aspergillus); diagnosed on an abnormal NBT / DHR (dihydrorhodamine) flow test.
In the exam
As a macrophage ingests a bacterium, a burst of oxygen consumption releases free radicals into the phagolysosome.
What settles it
Respiratory burst → superoxide FIRST (then H₂O₂ → HOCl). Lysozyme and defensins are oxygen-INDEPENDENT killing, NOT products of the burst.
Classically confused with
Lysozyme
Source: StatPearls — Chronic Granulomatous Disease