Impaired oxidative burst does not affect human monocyte tumoricidal activity

Area of Science:

• Immunology
• Cell Biology

Background:

• Human peripheral blood monocytes exhibit selective lysis of neoplastic cells.
• The oxidative burst, involving hydrogen peroxide and superoxide anion, has been hypothesized to mediate this monocyte tumoricidal activity.

Purpose of the Study:

• To investigate the role of the oxidative burst in mediating monocyte-mediated tumor cell lysis.

Main Methods:

• Studied two patients with chronic granulomatous disease (CGD) with impaired oxidative burst function.
• Assessed monocyte tumoricidal activity using 51Cr-release assays against K562, WEHI-164, and Daudi target cells.
• Evaluated tumoricidal activity of oxygen-deprived normal donor monocytes.

Main Results:

• A CGD patient with no detectable oxidative burst showed high monocyte tumoricidal activity against K562 and Actinomycin D-treated WEHI-164 cells.
• Another CGD patient with a reduced oxidative burst (15% of normal) efficiently killed Daudi targets.
• Normal monocytes, when deprived of oxygen and unable to produce an oxidative burst, still exhibited normal tumoricidal activity.

Conclusions:

• Reactive oxygen metabolites are not the primary mediators of tumor cell lysis by human peripheral blood monocytes.
• Monocyte tumoricidal activity can occur independently of a significant oxidative burst.