Concanavalin A capping in polymorphonuclear leukocytes

Beta-glucuronidase release from leukocytes in children

The release of beta-glucuronidase from polymorphonuclear leukocytes (PMNs) is important in the killing of bacteria and in producing tissue damage in acute inflammation. To investigate the effects of various diseases or drugs on degranulation, we studied the kinetics of beta-glucuronidase release from PMNs exposed to opsonized zymosan. PMNs of children with bacterial infections demonstrated increased degranulation. Within 5, 15, and 30 min the PMNs released 19 +/- 3%, 23 +/- 3%, and 26 +/- 3% of total beta-glucuronidase compared to 12 +/- 2%, 15 +/- 2%, and 16 +/- 2% of total beta-glucuronidase of control PMNs. Viral infections induced a significant delay of beta-glucuronidase release from PMNs. Maintenance therapy of acute lymphoblastic leukemia with 6-mercaptopurine and methotrexate, as well as administration of vincristine, diminished the degranulation. After 5, 15, and 30 min the PMNs released 8 +/- 1%, 10 +/- 1%, and 11 +/- 1%, as well as 6 +/- 3%, 8 +/- 2%, and 9 +/- 2% of total beta-glucuronidase. This study demonstrated that bacterial infections stimulate beta-glucuronidase release by PMNs. In contrast, cytostatic drugs inhibit lysosomal enzyme release, increasing the susceptibility to bacterial infections. The total enzyme activities were unchanged.

Concanavalin A distribution in polymorphonuclear leukocytes and alveolar macrophages during hyperoxia

Hyperoxia impairs cytoskeleton-dependent phagocytic functions in polymorphonuclear leukocytes (PMNs) and alveolar macrophages (AMs). To investigate the effect of different oxygen concentrations on the cytoskeleton, in particular the microtubule (MT) and microfilament (MF) system, the fluorescence pattern of Concanavalin A (Con A) receptors in AMs and PMNs was observed. Cells were obtained from guinea-pigs exposed to different oxygen concentrations. The exposure of guinea-pigs to oxygen concentrations of up to 50% induced in AMs and PMNs mainly spontaneous Con A capping, demonstrating an altered MT system. Oxygen tensions above 50% lead to an increased number of AMs and PMNs exhibiting a patchy Con A fluorescence distribution. Even in the presence of the microtubule-disrupting agent colchicine most AMs and PMNs were unable to form a Con A cap fluorescence distribution under these high oxygen tensions. This study demonstrates that the exposure of guinea-pigs to an oxygen concentration greater than 50% increases the relative number of AMs and PMNs demonstrating a patchy distribution of Con A. This patchy fluorescence pattern is associated with a severe cytoskeletal defect, i.e. MT and MF disruption. The various leukocyte function defects induced by hyperoxia, demonstrated in previous studies, are based on this MT and MF alteration in AMs and PMNs, representing an additional sepsis-promoting factor during hyperoxia.