DISTINCT INTRACELLULAR LYSOZYME CONTENT IN NORMAL GRANULOCYTES AND MONOCYTES - A QUANTITATIVE IMMUNOPEROXIDASE AND ULTRASTRUCTURAL IMMUNOGOLD STUDY

Using two different immunological methods, we performed a quantitative estimation of lysozyme (LZ) in normal mature granulocytes and monocyt es. An immunoperoxidase reaction for LZ in granulocytes and monocytes of 10 healthy donors measured by a scanning microdensitometer as arbit rary units showed a significantly higher LZ content in granulocytes th an in monocytes. An ultrastructural immunogold reaction (IGR) for LZ p erformed on post-embedded thin sections showed a higher number of tota l gold grains in neutrophilic granulocytes than in monocytes. In monoc ytic granules we found a high density of gold grains per mu m(2), wher eas in granulocytic granules lower values were obtained. In granulocyt es, LZ was found in both primary myeloperoxidase (MPO)-positive and se condary MPO-negative granules, and in monocytes the granules showed we ak MPO reactivity and high LZ content. Granulocytes previously subject ed to phagocytosis of bacteria and latex particles showed release of L Z on degranulation inside the phagosome, whereas in monocytes the gran ules remained outside the phagosome and released LZ without degranulat ion. Our study demonstrated a significantly higher total LZ content in granulocytes, a higher granular LZ content in monocytes, and release of LZ from intact monocyte granules during phagocytosis.