Related Experiment Videos
Aggregation of human polymorphonuclear leucocytes during phagocytosis of bacteria
Abstract:
The process of aggregation of human polymorphonuclear leucocytes (PMN) during the uptake of bacteria was studied. Radiolabelled S. aureus were opsonized in different sera, washed, resuspended in buffer and added to the PMN. Uptake of the bacteria and aggregation of the PMN were measured simultaneously. Maximal aggregation occurred within 6 min, when 5 X 10(6) PMN had phagocytosed 2.5 X 10(8) S. aureus. Also the effects of serum concentrations and different sera for opsonization of the bacteria on PMN aggregation were studied. Despite normal uptake, aggregation of PMN was low when bacteria were opsonized in complement-deficient sera. Furthermore when PMN were treated with pronase to inactivate complement receptors on the cell surface of the PMN, and bacteria preopsonized in immune serum were added, no change in uptake occurred, although the degree of aggregation halved compared to control PMN. So, interaction between the bacteria and the complement receptor of the PMN cell membrane is needed for triggering the process of aggregation. By using dansylcadaverin and diphenylamine to modulate lysosomal enzyme release, azide or PMN from a chronic granulomatous disease patient to study the effect of the formation of oxygen species, and theophylline, DB-cAMP or 8 Br-cAMP to increase cAMP levels, it was concluded that aggregation of PMN during phagocytosis was not dependent on oxygen metabolism, degranulation or cAMP levels of PMN.
Insights
Bacterial uptake by human polymorphonuclear leucocytes (PMN) triggers aggregation, but this process requires interaction with the PMN complement receptor. Oxygen metabolism, degranulation, and cAMP levels do not influence PMN aggregation during phagocytosis.
Area of Science:
- Immunology
- Cell Biology
- Microbiology
Background:
- Human polymorphonuclear leucocytes (PMN) play a crucial role in the innate immune response.
- Bacterial phagocytosis by PMN is a key mechanism for pathogen clearance.
- The process of PMN aggregation during bacterial uptake is not fully understood.
Purpose of the Study:
- To investigate the mechanisms underlying PMN aggregation during bacterial phagocytosis.
- To determine the role of complement receptors in PMN aggregation.
- To assess the involvement of oxygen metabolism, degranulation, and cAMP in PMN aggregation.
Main Methods:
- Studied aggregation of human PMN during uptake of radiolabelled S. aureus.
- Opsonized S. aureus in various sera and measured uptake and aggregation.
- Utilized pronase treatment to inactivate complement receptors on PMN.
- Investigated effects of lysosomal enzyme release modulators, oxygen species formation, and cAMP levels.
Main Results:
- Maximal PMN aggregation occurred within 6 minutes of phagocytosis.
- Aggregation was reduced when bacteria were opsonized in complement-deficient sera.
- Inactivating complement receptors halved PMN aggregation without affecting bacterial uptake.
- PMN aggregation was independent of oxygen metabolism, degranulation, and cAMP levels.
Conclusions:
- Interaction between bacteria and the complement receptor on the PMN cell membrane is essential for triggering aggregation.
- PMN aggregation during phagocytosis is not dependent on oxygen metabolism, degranulation, or cAMP levels.