Inhibition of HLA-DR expression on activated human blood eosinophils by transforming growth factor-beta1.

1998 
Peripheral blood, bronchoalveolar lavage and sputum eosinophils of patients with asthma but not peripheral blood eosinophils from normal controls have been shown to express human leucocyte antigen (HLA)-DR on their cell surface. Cytokines implicated in the activation of eosinophils, such as interleukin (IL)-3 and granulocyte‐macrophage colony-stimulating factor (GM-CSF), can up-regulate HLA-DR expression. However, little is known about antagonistic factors that might down-regulate HLA-DR expression on eosinophils. In this study we investigated whether transforming growth factor-b (TGF-b), which has been shown to reduce survival of activated eosinophils, can also modulate HLA-DR expression on eosinophils. For this purpose, isolated peripheral blood eosinophils were stimulated with IL-3 and GM-CSF for 24 h and HLA-DR expression was measured by flow cytometry. We found that while isolated eosinophils expressed low levels of surface HLA-DR, incubation with GM-CSF and IL-3 increased HLA-DR expression on eosinophils. TGF-b alone did not change HLA-DR expression on isolated eosinophils. However, co-incubation of eosinophils with TGF-b and either GM-CSF or IL-3 significantly decreased HLA-DR expression compared to eosinophils incubated with either GM-CSF or IL-3 alone and this was not reversed by addition of IL-5. This effect of TGF-b on IL-3-induced HLA-DR expression was attenuated dose-dependently in the presence of monoclonal anti-TGF-b antibodies. Our results suggest that TGF-b can reduce cytokine-induced HLA-DR expression on eosinophils and could thus influence eosinophil activation.
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