The activated eosinophil in allergy and asthma

Area of Science:

• Immunology
• Cell Biology

Background:

• Human eosinophils are implicated in allergic inflammation.
• Eosinophil activation involves surface receptor changes, lipid generation, and cytotoxicity.
• Immunoglobulin (IgE, IgG) and complement pathways mediate eosinophil activation.

Purpose of the Study:

• To investigate the activation mechanisms of human eosinophils.
• To identify key mediators involved in eosinophil recruitment and activation in allergic inflammation.

Main Methods:

• In vitro studies assessing eosinophil activation by pharmacological mediators.
• Evaluation of chemotactic responses to various cytokines and platelet-activating factor (PAF).
• Correlation of in vivo eosinophil infiltration with T cell activation markers (CD4+, IL-2 receptor+).

Main Results:

• Eosinophils are activated by various mediators via IgE-, IgG-, and complement-dependent pathways.
• Platelet-activating factor (PAF) is a potent eosinophil activator and chemoattractant, but not selective.
• Cytokines like IL-1, IL-2, GM-CSF, TNF, IFN-γ, and IL-5 showed weak in vitro chemotaxis for eosinophils.
• In vivo, eosinophil infiltration in allergic reactions correlates with local activated T cell accumulation.

Conclusions:

• Lipid mediators like PAF initially recruit and activate granulocytes.
• Subsequent selective activation of eosinophils by cytokines may explain their infiltration in allergic inflammation.
• The interplay between lipid mediators and cytokines is crucial in orchestrating eosinophil responses in allergy.