IL-3 induces B7.2 (CD86) expression and costimulatory activity in human eosinophils

Area of Science:

• Immunology
• Cell Biology
• Allergy and Parasitic Diseases

Background:

• Eosinophils interact with T cells in allergic and parasitic diseases.
• Resting eosinophils lack MHC class II and B7 molecules, failing to stimulate T cells.
• Cytokines like IL-5 and GM-CSF can induce antigen-presenting capabilities in eosinophils.

Purpose of the Study:

• To investigate the role of Interleukin-3 (IL-3) in activating eosinophils for antigen presentation.
• To compare IL-3's effect with IL-5 and Granulocyte-Macrophage Colony-Stimulating Factor (GM-CSF) on eosinophil antigen presentation.
• To determine if eosinophils are capable of processing and presenting native antigens to T cells.

Main Methods:

• Eosinophils were treated with IL-3, IL-5, or GM-CSF.
• Expression of MHC class II and B7 molecules (B7.1, B7.2) on treated eosinophils was assessed.
• T cell proliferation assays were performed using superantigens and specific antigenic peptides or native antigens.

Main Results:

• IL-3-treated eosinophils expressed HLA-DR and B7.2, promoting T cell proliferation to superantigens and antigenic peptides.
• This proliferation was dependent on B7.2 and inhibited by anti-B7.2 monoclonal antibody (mAb).
• IL-3, IL-5, and GM-CSF treated eosinophils failed to present native antigens to T cells, indicating a processing deficiency.

Conclusions:

• Eosinophils activated by IL-3 can present superantigens and antigenic peptides to T cells, suggesting a role in immune modulation.
• Despite cytokine-induced expression of costimulatory molecules, eosinophils exhibit a deficiency in native antigen processing.
• Activated eosinophils may contribute to T cell activation in disease contexts through peptide and superantigen presentation.