RESUMEN
Dendritic cells (DCs) are professional APCs involved in the initiation of both immunity and immunological tolerance. In autoimmune diseases or graft rejections, most reactive lymphocytes are effector/memory cells. It is believed that memory T cells are more resistant to tolerance induction than naive lymphocytes; however, studies on mechanisms for their efficient tolerization are still scarce. In this study, we generated human monocyte-derived DCs by culture with GM-CSF and IL-4 (control DCs), as well as tolerogenic DCs (tDCs) by adding IL-10, IL-10/TGF-beta1, or IL-10/IL-6. Cells were maturated with TNF-alpha/PGE(2). Compared with control DCs, tDCs had similar expression of HLA-DR, CD80, and CD86, lower expression of CD40, higher levels of macrophage markers, enhanced endocytic ability, increased secretion of IL-6, IL-10 (only tDCs generated with IL-10 and tDCs generated with IL-10/IL-6), and PGE(2), and lower secretion of IL-12 and IL-23. In vitro, tDCs had the capacity to induce anergy in tetanus toxoid-specific memory CD4(+) T cells, whereas the proliferative response to an unrelated Ag was intact. Anergy could be reverted upon exposure to IL-2. tDC-primed T cells have low suppressive ability. Nevertheless, the generation of both anergic and regulatory T cells was more efficient with tDCs generated with IL-10/TGF-beta1. Microarray-based gene expression profiling reflected modulated expression of several transcripts in tDCs. Surface CLIP-HLA-DR complexes and intracellular thrombospondin-1 were increased in the three tDCs. CD39 was highly expressed only in tDC-TGF, which correlated with increased adenosine production. We propose that these molecules, together with IL-10 and prostanoids, are key factors to induce Ag-specific tolerance in memory T cells.
