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Platelet-dependent generation of chemotactic activity in serum
The Journal of Experimental Medicine
|June 1, 1973
Summary
Human platelets release a protein that activates complement, specifically the fifth component (C5), to attract immune cells. This process mimics leukocyte function and suggests platelets
Area of Science:
- Immunology
- Hematology
- Biochemistry
Background:
- Platelets are known for their role in hemostasis and thrombosis.
- Their potential involvement in inflammatory processes is less understood.
- Leukocytes are key mediators of chemotaxis through complement activation.
Purpose of the Study:
- To investigate whether human platelets can generate chemotactic activity.
- To elucidate the mechanism of platelet-mediated chemotaxis.
- To determine the role of complement activation in this process.
Main Methods:
- Extraction of a protein fraction from human platelet lysosomal granules.
- Incubation of the platelet factor with fresh human serum.
- Assay of chemotactic activity for polymorphonuclear leukocytes.
- Investigation of complement component involvement (C3, C5) and effect of heat or antibody treatment on serum.
Main Results:
- A platelet protein fraction induced chemotactic activity in fresh serum.
- This activity was released upon platelet aggregation (collagen, epinephrine) and during blood clotting.
- Complement component C5, but not C3, was responsible for generating chemotactic activity when incubated with the platelet factor.
- Heat-inactivated serum or serum treated with anti-C5 antibody abolished activity.
Conclusions:
- Human platelets possess a factor that stimulates chemotaxis via complement activation.
- Platelet-derived factor activates the fifth component of complement (C5).
- Platelets may play a role in initiating inflammatory responses by attracting leukocytes.