Lysozyme in human neutrophils and plasma. A parameter of myelopoietic activity

Lysozyme was found to be present in all three types of human neutrophil granules (azurophil-, specific- and gelatinase granules) as determined by subcellular fractionation, employing a three-layer Percoll gradient and measurement of lysozyme by a novel ELISA. The content of lysozyme was also measured in plasma. In contrast to other neutrophil granule proteins (lactoferrin, NGAL, and gelatinase), plasma lysozyme was unaffected by increase in the number of circulating neutrophils induced by intravenous administration of methylprednisolone to healthy individuals. Also in contrast to lactoferrin, NGAL, and gelatinase, plasma lysozyme was found to rise 1 week prior to detectable increases in the number of circulating neutrophils in patients undergoing allogeneic bone marrow transplantation. We conclude that plasma lysozyme is a parameter of myelopoietic activity and may be useful as a marker for bone marrow repopulation after transplantation.