Neutrophilic Leukocytes in Immunologic Reactions: Evidence for the Selective Release of Lysosomal Constituents

The release of lysosomal bioactive factors is essential to the role of the neutrophilic leukocyte as a mediator of tissue injury in immunologic inflammatory lesions. The lysosomal release process was studied by exposing rabbit neutrophils to phagocytosable immune complexes, non-phagocytosable immune complexes and antineutrophil antibody and measuring the kinetics of release of a lysosomal marker enzyme (β glucuronidase). All three types of immunologic stimuli produced a rapid, selective release of the lysosomal marker. This release preceded that of a cytoplasmic marker enzyme (lactic dehydrogenase) and was not associated with a general increase in cell membrane permeability as judged by trypan blue dye exclusion. In contrast when neutrophils were exposed to a cytotoxic chemical, N-ethylmaleimide, the opposite pattern was observed. Lactic dehydrogenase was rapidly released while release of β glucuronidase was greatly delayed. These studies indicate that there is a non-cytotoxic, non-cytolytic mechanism for the immunologically induced release of neutrophil lysosomal bioactive factors. This process may be similar to the non-cytolytic release mechanisms described for other cells such as platelets and mast cells.