Hypoxemia/reoxygenation down-regulates interleukin-8-stimulated bactericidal activity of polymorphonuclear neutrophil by differential regulation of CD16 and CD35 mRNA expression.
BACKGROUND
The purpose of this study was to determine the effects of hypoxemia/reoxygenation (H/R) on the regulation of interleukin-8 (IL-8)-stimulated human polymorphonuclear neutrophil (PMN) bactericidal activity.


METHODS
Venous human whole blood was rendered normoxic (Pvo2 saturation 60% to 80%), hypoxemic (Pvo2 saturation, less than 15%), or H/R (Pvo2 saturation more than 97%) by dialyzing the blood against a gas mixture of N2/H2/CO2 +/- 30% O2. Two hundred microliter aliquots from each study group were incubated with IL-8 (50 ng/ml) for 45 minutes before fluorescein isothiocyanate-conjugated mouse antihuman CD16 or CD35 antibodies were added. Bactericidal activity was measured with the release of 51Cr from labeled bacteria at 1:1, 5:1, and 10:1 PMN-target ratios. Steady-state mRNA levels for CD16 and CD35 were quantified by Northern blot analyses.


RESULTS
H/R reduced PMN bactericidal activity compared with hypoxemic levels for staphylococcus aureus (48 +/- 5.6 versus 27 +/- 3.3) and Escherichia coli (58 +/- 7.1 versus 33 +/- 4.2). H/R reduced the surface expression of CD16 but not CD35 (mean channel fluorescence CD16, 610 +/- 70 versus 310 +/- 30 for hypoxemia versus H/R; p < 0.01). After H/R was performed, IL-8 decreased mRNA levels for CD16 but not for CD35 compared with levels seen during hypoxemia + IL-8.


CONCLUSIONS
H/R down-regulates IL-8-stimulated PMN bactericidal activity by decreasing steady-state mRNA levels and surface expression of CD16. PMN bactericidal capability after H/R + IL-8 is primarily complementary and not Fc gamma receptor dependent.
Knowles
R
R
Department of Surgery, Brown University School of Medicine, Rhode Island Hospital, Providence 02903, USA.
Keeping
H
H
Nguyen
K
K
Graeber
T
T
D'Amico
R
R
Simms
H
H
D001770:Blood Bactericidal Activity; D015152:Blotting, Northern; D015870:Gene Expression / Q000276:immunology; D006801:Humans; D000860:Hypoxia / Q000276:immunology / Q000503:physiopathology*; D016209:Interleukin-8 / Q000502:physiology*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D019255:NADPH Oxidases; D009504:Neutrophils / Q000201:enzymology / Q000276:immunology*; D010100:Oxygen / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017463:Receptors, Complement 3b / Q000235:genetics*; D017452:Receptors, IgG / Q000235:genetics*
D016209:Interleukin-8; D012333:RNA, Messenger; D017463:Receptors, Complement 3b; D017452:Receptors, IgG; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; D010100:Oxygen