Apoptotic cells selectively suppress the Th1 cytokine interferon γ in stimulated human peripheral blood mononuclear cells and shift the Th1/Th2 balance towards Th2

Abstract

Apoptotic cells are readily recognized and engulfed by phagocytes and usually do not induce inflammation or tissue damage. Furthermore, they can actively suppress a pro-inflammatory response in phagocytes: In the presence of apoptotic cells, activated monocytes/macrophages produce more of the anti-inflammatory and immunoregulatory cytokines IL-10 and TGF-β, but less of the pro-inflammatory cytokines TNFα, IL-1β and IL-12. This immunoregulatory effect is most likely mediated by several receptors on monocytes/macrophages including the thrombospondin receptor (CD36). In addition to the modulation of cytokine secretion, apoptotic cell material inhibited the expression of MHC class II molecules on the surface of monocytes/macrophages. Decreased MHC II expression appeared to be mediated predominantly by increased IL-10 secretion in a para-/autocrine manner. Here, we show that the functional modulation of antigen-presenting monocytes/macrophages by apoptotic cells also influences T cell activation and function. When human peripheral blood mononuclear cells were stimulated with recall antigens in the presence of apoptotic cells, interferonγ (IFNγ) secretion was markedly suppressed, whereas secretion of the Th2 cytokine IL-4 was not significantly altered. Hence, apoptotic cells shift the T cell cytokine secretion pattern towards a Th2-like response. This Th2 shift can largely be prevented by neutralizing IL-10, indicating an important role of this cytokine for modulating T cell cytokine secretion patterns.

• Apoptotic cells
• antigen presenting cells
• monocytes
• macrophages
• Th1 cells
• Th2 cells

Acknowledgements

This work is supported by the Interdisciplinary Center for Clinical Research (IZKF, project number N2) and the ELAN fonds of the University Hospital Erlangen to Reinhard Voll. Damian Maseda was supported by a stipend through the Research Training Grant GK592 from the Deutsche Forschungsgemeinschaft and by intramural funding from the University of Erlangen's ELAN program. ELAN Fonds of the University Hospital Erlangen to R. Voll.