Related Experiment Videos
Comparative platelet inhibitory effects of human neutrophils and lymphocytes
F A Nicolini1, A C Wilson, P Mehta
1Department of Medicine, University of Florida College of Medicine, Gainesville.
Abstract:
The effects of isolated leukocytes (polymorphonuclear leukocytes [PMNLs] or neutrophils and lymphocytes) on platelet aggregation in platelet-rich plasma (PRP) were examined. Both PMNLs and lymphocytes decreased platelet aggregation in a concentration-dependent fashion. PMNL-induced, but not lymphocyte-induced, inhibition of platelet aggregation was more pronounced as the incubation time of PRP with PMNLs was prolonged. The platelet-inhibitory effect of PMNLs was enhanced by superoxide dismutase (SOD) and was attenuated by oxyhemoglobin and methylene blue. These agents, in contrast, had no effect on lymphocyte-mediated inhibition of platelet aggregation. Adenosine deaminase did not modulate the platelet inhibitory effects of either PMNLs or lymphocytes. The incubation of PMNLs with PRP was associated with an increase in cyclic guanine 5' monophosphate (cGMP) levels in PRP. Incubation of lymphocytes, however, did not result in an increase in cGMP levels in PRP. Neither PMNLs nor lymphocytes in PRP caused a reduction in thromboxane B2 (TXB2) or an increase in 6-keto-PGF1 alpha. Thus this study shows potent inhibitory effects of isolated PMNLs mediated by a substance with biologic characteristics of nitric oxide. However, the mechanism of lymphocyte-induced inhibition of platelets appears to be independent of prostaglandins, nitric oxide, or adenosine.
Insights
Isolated leukocytes, including polymorphonuclear leukocytes (PMNLs) and lymphocytes, inhibit platelet aggregation. PMNLs exhibit a time-dependent inhibition, potentially mediated by nitric oxide, while lymphocyte effects differ.
Area of Science:
- Immunology
- Hematology
Background:
- Leukocytes play a role in hemostasis and thrombosis.
- Understanding leukocyte-platelet interactions is crucial for cardiovascular research.
Purpose of the Study:
- To investigate the effects of isolated polymorphonuclear leukocytes (PMNLs) and lymphocytes on platelet aggregation.
- To elucidate the mechanisms underlying leukocyte-mediated platelet inhibition.
Main Methods:
- Platelet-rich plasma (PRP) was incubated with isolated PMNLs or lymphocytes.
- Platelet aggregation was measured.
- Effects of various agents (superoxide dismutase, oxyhemoglobin, methylene blue, adenosine deaminase) were assessed.
- Cyclic guanine 5' monophosphate (cGMP), thromboxane B2 (TXB2), and 6-keto-PGF1 alpha levels were measured.
Main Results:
- Both PMNLs and lymphocytes inhibited platelet aggregation in a concentration-dependent manner.
- PMNL-induced inhibition increased with incubation time and was modulated by agents affecting nitric oxide pathways.
- Lymphocyte-induced inhibition was not affected by these agents.
- PMNL incubation increased PRP cGMP levels, while lymphocyte incubation did not.
- Neither cell type altered TXB2 or 6-keto-PGF1 alpha levels.
Conclusions:
- Isolated PMNLs potently inhibit platelet aggregation, likely via nitric oxide.
- Lymphocyte-mediated platelet inhibition appears to involve mechanisms independent of nitric oxide, prostaglandins, or adenosine.