An electron microscopic study of human polymorphonuclear leukocyte injury induced by rabbit antiserum

Electron microscopic examination of human leukocytes treated with antiserum revealed marked degenerative changes. These changes appeared limited to PMN's. Initial alterations included loss of cytoplasmic density and focal aggregation of granules against the plasma membrane. Nuclear chromatin became homogeneous and less dense. There were no morphologic changes suggesting intracytoplasmic granule lysis. Degenerating PMN's apparently fragmented and released cytoplasmic structures into the medium. Portions of cell debris were ingested by undamaged PMN's and monocytes. The changes described above did not occur in divalent cation-depleted plasma, suggesting that the damage is complement-dependent. However, in preparations devoid of divalent cations, PMN's developed increased pseudopod activity and formed peculiar, lamellar vesicles thought to represent cell surface response to antiserum. It is postulated that antibodies directed against PMN's may damage these cells and cause release of lysosomal material.