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Abstracts of the 18th Annual Meeting of the American Society of Transplantation (AST), May 15-19, 1999, Chicago, Illinois

DIFFERENTIAL EFFECTS OF DENDRITIC CELLS OVEREXPRESSING MAMMALIAN IL-10 ON ORGAN ALLOGRAFT AND ANTI-TUMOR IMMUNITY

Lu, L; Lee, W C; Li, W; Wan, Y; Xing, Z; Gauldie, J; Thomson, A W; Fung, J J.; Qian, S

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Abstract 966

IL-10 has been shown to inhibit the maturation of dendritic cells (DC) by downregulation of MHC class II, co-stimulatory and adhesion molecule expression. Administration of mouse bone marrow (BM)-derived DC propagated in GM-CSF and TGFβ1 ('TGFβ DC'), that are phenotypically immature (MHC class II+, CD40low, CD80low, CD86low), prolongs donor-specific mouse cardiac allograft survival. Overexpression of IL-10 in 'TGFβ DC' might enhance their tolerogenicity. In the present study, genes encoding murine IL-10 were transduced into B10 (H-2b) BM-derived 'TGFβ DC' using adenoviral (Ad) vectors (LacZ as reporter). Their immunostimulatory properties were determined in vitro by MLR and CTL generation assays, and in vivo by their influence on rejection of B10 cardiac allograft survival in C3H (H-2k) recipients, as well as their influence on growth of B16F10 murine melanoma (H2b) in B6 (H2b) mice. 'TGFβ DC' transduced with Ad-LacZ at 50-100 MOI (multiplicity of infection) did not affect the in vivo DC migration pattern, as detected by tissue staining for both donor MHC class II and X-gal following footpad injection into C3H mice. Ad-IL-10-transduced 'TGFβ DC' producing 6.2 ng IL-10/106 cells/d displayed downregulation of MHC class II expression compared with Ad-LacZ controls (from 46.6 to 33.3%), CD80 (from 39.6 to 27.1%), and CD86 (from 27.2 to 18.7%). Transduction with Ad-IL-10 however, enhanced DC allostimulatory activity in MLR assay (cpm 22773 ± 797 vs 11617 ± 1274 in Ad-LacZ controls at S:R ratio = 1:20), CTL (38.5 ± 3.4% vs 10.3 ± 0.9% in Ad-LacZ controls at E:T ratio of 100:1) and NK cell activity (46.3 ± 4% vs 14.6 ± 0.9% in Ad-LacZ controls at R:T ratio of 100:1). Administration of (2 × 106) B10 BM-derived Ad-IL-10 transduced 'TGFβ DC' to C3H recipients 7d before receiving B10 cardiac grafts exacerbated graft rejection (median survival time 3.5 days [n = 6] vs 13 days [n = 5]) in Ad-LacZ controls. In contrast, IL-10 transduction inhibited the anti-tumor effect of antigen-pulsed DC (B16F10-DC). All animals immunized with IL-10 transduced B16F10-DC had tumor growth in 40 days, while all animals treated with non-IL-10-transduced B16F10-DC were tumor free. The generation of tumor specific CTL in spleen cells from animals immunized by B16F10-DC transduced with Ad-IL-10 was significantly inhibited (10% vs 53% in mice immunized with non-transduced B16F10-DC at E:T ratio of 90:1). These findings reflect the complex (multifunctional) immune regulatory properties of IL-10, and support our previous observation that the immunosuppressive action of IL-10 appears more effective on indirect antigen recognition (tumor antigen recognition) than on direct (allo) recognition.

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