The effect of Fe3+ bound lactoferrin (LF) on chemiluminescence (CL) generation in human monocytes in the presence and absence of opsonized zymosan was examined. Fe3+ bound LF (10-6 or 10-7 M) augmented the CL response in the presence but not the absence of zymosan. In contrast, Apo LF, Fe3+ bound transferrin and Fe3+ itself had no significant effect. It appears that the effect of LF on zymosan-induced chemiluminescence is dependent on iron and is receptor specific. The augmentation of CL by LF was inhibited by superoxide dismutase (SOD) and ETYA (fatty acid cyclooxygenase and lipoxygenase inhibitors), but not indomethacin (fatty acid cyclooxygenase inhibitor). Thus the enhancement of CL by LF depends on superoxide anion production and is related to the lipoxygenase pathway. The significance of this observation in terms of microbicidal or tumoricidal mechanisms remains to be determined.
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