Chemiluminescence of Human and Canine Polymorphonuclear Leukocytes in the Absence of Phagocytosis

Open Access
Publisher Website
Google Scholar
Abstract
Polymorphonuclear leukocytes (PMNs) have increased oxidative metabolism during phagocytosis and emit light (chemiluminescence, CL) as a result of metabolic activation. The present study examined PMN CL in the absence of phagocytosis using sodium fluoride (NaF), a nonparticulate agent and known stimulator of cellular oxidative metabolism. Normal human and canine PMNs were assayed in a CL spectrometer which permitted continuous sample mixing and constant temperature regulation during CL measurement. PMNs treated with 20 mM NaF demonstrated maximum CL responses of 10,000-20,000 cpm above background, 13-17 min after addition of NaF at 37°C. Temperature regulation of reaction mixtures was found to be a critical factor in assaying PMN CL responses to NaF, because a small decrease in temperature (i.e. 1.5°C) substantially depressed and delayed the CL response. Superoxide anion production correlated closely with CL responses in NaF-treated human PMNs. CL responses were completely suppressed in the presence of the oxidative metabolic inhibitors, iodoacetamide, and N-ethylmalemide; and were partially suppressed in the presence of either superoxide dismutase or sodium azide. CL responses of NaF-treated PMNs were significantly lower than responses generated by PMNs phagocytizing opsonized yeast. When NaF was evaluated for its effect on light generation from a singlet oxygen dependent CL reaction, it was found that NaF did not quench singlet oxygen light. This study demonstrates that PMN CL can occur in the absence of phagocytosis, and it proposes that a nonphagocytic PMN CL assay may be useful in evaluating leukocyte metabolic defects.