Abstract
Heparin is bound with heparin-binding sites on certain cells, which induces proliferation and differentiation signals. In addition, heparin is bound with heparin-binding domains of various cytokines, which enhances the interaction between cytokines and target cells. Monocytes have been demonstrated to posses heparin-binding sites on cell surfaces. In the present study, we investigated the effects of heparin (including low molecular weight heparin) and heparan sulfate on antigen presentation and antigen-specific CTL induction of monocyte-derived DCs. Peripheral blood CD14+ cells were cultured to generate immature and mature DCs with various concentrations of heparin, low molecular weight heparin or heparan sulfate. Cultured cells were analyzed for DC-associated surface phenotypes by flow cytometry and evaluated for allogeneic antigen presenting ability by mixed leukocyte culture. In order to evaluate the effects of heparin on monocyte-derived DCs to generate antigen-specific CTL, DCs were generated from HLA-A2402 donors by serum-free culture with heparin, transfected with in vitro transcribed WT-1 mRNA on day 6 and cultured with the addition TNF-α/IL-1α/IL-6/IFN-γ/PGE2 for further 1 day. WT-1 mRNA-transfected DCs were used for priming autologous lymphocytes in co-culture at the stimulator:responder ratio of 1:10. Lymphocytes were primed with the same DCs 2-3 times in the interval of 5-7 days. CD8+ T cells were separated and used as effector cells in 51Cr-release assay. WT-1 expressing and HLA-A24+ cell line MegO1 was used as target cells. In order to evaluate the association of MHC molecules in the cytotoxicity, 51Cr-lebelled target cells were treated with anti-MHC class I or class II monoclonal antibody before cytotoxicity assay. In order to evaluate the antigen specificity of the generated CTL, unlabelled target cells were added to the cytotoxicity assay. By the addition of heparin, the expression of CD1a and CD80 on both immature and mature DCs was markedly enhanced and the allogeneic antigen presenting ability was elevated in both immature and mature DCs. By the addition of low molecular weight heparin, the expression of CD1a was enhanced and antigen presenting ability was elevated also. By the addition of heparan sulfate, similar results of elevated antigen presentation were obtained. By the priming of lymphocytes with WT-1 mRNA transfected DCs generated from monocytes by the serum-free culture with heparin, cytotoxic capability against WT-1 expressing target cells was demonstrated in the primed lymphocytes. The cytotoxic capability of the lymphocytes was blocked by the treatment of the target cells with anti-MHC class I monoclonal antibody and the addition of unlabelled target cells in the cytotoxicity reaction. The present study demonstrated that heparin/low molecular weight heparin/heparan sulfate could enhance the antigen presentation and antigen-specific CTL induction of monocyte-derived DCs. These findings suggest the usefulness of heparin for generating efficient DCs for DC-based immunotherapy and the involvement of heparan sulfate in immunological defense mechanism.
Binding of hyaluronate to the surface of cultured cells.