Poly(I:C)-Treated Human Langerhans Cells Promote the Differentiation of CD4+ T Cells Producing IFN-[gamma] and IL-10

• Published in: Journal of investigative dermatology Vol. 129; no. 8; p. 1963
• Main Authors: Furio, Laetitia, Billard, Hermine, Valladeau, Jenny, Péguet-navarro, Josette, Berthier-vergnes, Odile
• Format: Journal Article
• Language: English
• Published: London Elsevier Limited 01-08-2009
• ISSN: 0022-202X; 1523-1747
• DOI: 10.1038/jid.2009.21

Epidermal Langerhans cells (LCs) are the first dendritic cells to encounter skin pathogens. However, their function has recently been challenged, especially in the initiation of T-cell responses to viral antigens. We have previously reported that fresh immature human LCs express mRNA encoding TLR3. Here we analyze the response of highly purified human LCs to poly(I:C), a synthetic mimetic of viral dsRNA recognized by TLR3. We show that LCs exposed for 2 days to poly(I:C) under serum-free conditions up-regulated co-stimulatory molecules, a process associated with increased allostimulatory capacity. Furthermore, poly(I:C) significantly enhanced LC survival and induced them to produce CXCL10, IL-6, and IL-12 p40. Bioactive IL-12 p70, IL-1beta, IL-15, IL-18, and IL-23 were never detected, even after CD40 ligation. LC incubation in the presence of bafilomycin completely reversed the effect of poly(I:C) on LC phenotypic activation and survival, indicating that endosomal TLR3 is involved in this process. Most interestingly, we report here that poly(I:C)-treated LCs favored alloreactive CD4(+) T-cell differentiation toward a Th1 profile and concomitant differentiation of IL-10-producing CD4(+) T cells that might limit, at another time, the inflammatory response and subsequent tissue damage.