MORPHOLOGICAL HETEROGENEITY OF MYELOPEROXIDASE-POSITIVE GRANULES IN NORMAL CIRCULATING NEUTROPHILS - AN ULTRASTRUCTURAL-STUDY BY CRYOSECTION

Ultrastructural localization of myeloperoxidase (MPO) in the granules of human circulating neutrophils was examined by cryosection. On caref ul comparison with the morphological characteristics of the granules b y conventional transmission electron microscopic study, large MPO-posi tive granules were divided into five types by immunocryoultramicrotomy using monoclonal antibody. Double staining of MPO and lactoferrin (or lysozyme) was also performed. Lactoferrin was generally detected in M PO-negative granules. Lysozyme immunostaining was present in MPO-posit ive and -negative granules. These data may suggest different functions among large MPO-positive granules of human circulating neutrophils.