Related Experiment Videos
Characterization of polymorphonuclear leukocyte aggregation in vitro induced by heat-inactivated group B
Abstract:
We studied the aggregatory characteristics of human polymorphonuclear leukocytes (PMNs) in response to heat-inactivated group B streptococcus. PMNs suspended in physiologic salt solution do not aggregate to heat-inactivated group B streptococcus (GBS) unless the GBS is previously opsonized in autologous plasma. The aggregating activity of both opsonized GBS and activated plasma are reduced if the plasma is decomplemented before incubation with GBS. Pretreatment of PMNs with pronase inhibited opsonized GBS-induced aggregation, suggesting aggregation via cell membrane receptors for opsonic fragments of C3. Pronase pretreatment had no significant effect on aggregation induced by activated plasma or arachidonic acid. Unlike PMNs in physiologic salt solution, PMNs suspended in plasma aggregate when stimulated by unopsonized GBS. GBS aggregates PMNs via complement cascade activation, opsonization, and interaction with cell membrane receptors to stimulate cellular mechanisms resulting in PMN aggregation.
Insights
Human polymorphonuclear leukocytes (PMNs) aggregate to opsonized group B streptococcus (GBS) via complement C3 receptors. Unopsonized GBS also aggregates PMNs in plasma, indicating complement cascade activation is key for PMN aggregation.
Area of Science:
- Immunology
- Cell Biology
- Microbiology
Background:
- Polymorphonuclear leukocytes (PMNs) are crucial immune cells involved in pathogen clearance.
- Group B Streptococcus (GBS) is a significant pathogen, particularly in neonatal infections.
- Understanding PMN aggregation mechanisms is vital for developing effective immunotherapies.
Purpose of the Study:
- To investigate the aggregatory characteristics of human PMNs in response to GBS.
- To elucidate the role of complement opsonization and plasma in GBS-induced PMN aggregation.
- To identify the specific receptors and pathways involved in PMN aggregation.
Main Methods:
- Incubation of human PMNs with heat-inactivated GBS in various conditions (physiologic salt solution, autologous plasma).
- Opsonization of GBS with autologous plasma and subsequent incubation with PMNs.
- Complement depletion of plasma and its effect on GBS-induced PMN aggregation.
- Pronase pretreatment of PMNs to assess the role of cell membrane receptors.
Main Results:
- PMNs in physiologic salt solution did not aggregate with unopsonized GBS.
- Opsonization of GBS in autologous plasma was necessary for PMN aggregation in salt solution.
- Pronase pretreatment inhibited opsonized GBS-induced aggregation, suggesting C3 receptor involvement.
- PMNs suspended in plasma aggregated with unopsonized GBS, indicating complement cascade activation.
Conclusions:
- GBS aggregates PMNs through a mechanism involving complement cascade activation and opsonization.
- Cell membrane receptors for opsonic fragments of C3 play a significant role in GBS-induced PMN aggregation.
- Plasma facilitates GBS-induced PMN aggregation, highlighting the importance of complement in this process.