Towards the development of artificial antigen-presenting cell (APP3P.116)

Abstract

Abstract T cell programming into distinct T cell subsets depends in a large extent from the quality and quantity of the signal delivered to T cells by professional antigen presenting cells (APC). However, it is difficult to vary parameters of T cell stimulation using live APC. To calibrate the strength of naïve T cell stimulation, we are developing artificial antigen-presenting cell (APC) that display nanolipoprotein particles (NLPs) presenting pMHC and other ligands incorporated into lipid bilayers built on a glass beads. Soluble analogs of the pMHC assembled on NLPs permits to control the extent of the homotypic ligand clustering and to influence the strength of T cell stimulation. We have found that the apparent equilibrium binding constants of an agonist pMHC/NiNLPs were strongly dependent on pMHC density. A higher density of pMHC on NiNLPs resulted in a much stronger response even though the concentration of the pMHC/NiNLPs at the lower pMHC density was 10-fold higher. We have also demonstrated that bilayers on glass beads were fluid allowing the mobility of pMHC/NLPs on the surface of engineered APC. In a model experiment, T cells concentrated the ICAM-1/pMHC/NLPs conjugates at the contact surface indicating that these conjugates were able to move on the bilayers mimicking direction stimulation of the T cells with live APC. These and other data will be discussed to demonstrate the utility of engineered APC for stimulation of naïve T cells ex vivo.