Partial purification and biological properties of an eosinophil-activating factor

Area of Science:

• Immunology
• Parasitology
• Cell Biology

Background:

• Eosinophils play a crucial role in host defense against parasites and virus-infected cells.
• The mechanisms by which eosinophils are activated and enhance their cytotoxic functions are not fully understood.

Purpose of the Study:

• To identify and characterize a protein that enhances eosinophil-mediated killing of antibody-coated schistosomula of Schistosoma mansoni.
• To investigate the functional effects of this protein on eosinophil activity, including degranulation and respiratory burst.

Main Methods:

• Partial purification of eosinophil-activating factor (EAF) from cultured peripheral blood mononuclear cell supernatants using Sephacryl S-200 and DEAE-cellulose chromatography.
• Assessment of EAF's effect on eosinophil-mediated killing of antibody-coated schistosomula and herpes simplex virus-infected Chang liver cells.
• Measurement of eosinophil superoxide and hydrogen peroxide production, and degranulation in response to EAF.

Main Results:

• EAF was partially purified and characterized as an acidic protein with a molecular mass of approximately 40 kDa.
• EAF enhanced eosinophil killing of antibody-coated schistosomula and virus-infected cells.
• EAF stimulated eosinophil degranulation, leading to the release of eosinophil peroxidase and eosinophil cationic protein, but the enhancement of respiratory burst activity did not fully explain the increased killing capacity.

Conclusions:

• Eosinophil-activating factor (EAF) enhances eosinophil effector functions.
• EAF's primary mechanism for increasing parasite and virus-infected cell killing involves promoting eosinophil degranulation and the release of cytotoxic granule proteins.
• These findings identify EAF as a key mediator in eosinophil-mediated immunity.