Abstract 3533: Acquisition of antigen presenting cell functions by Vγ9Vα2-T cells requires trogocytosis

Abstract

Abstract Invariant Natural Killer T (iNKT) cells are an important immunoregulatory T cell subset that is restricted by the CD1d Ag-presenting molecule. When activated by the glycolipid α-galactosylceramide (α-GalCer) iNKT produce large amounts of cytokines that play an important role in initiating and orchestrating antitumor immune responses. Early clinical trials with α-GalCer-pulsed monocyte derived dendritic cells (DC) have shown anecdotal antitumor activity in advanced cancer. It has been reported that phosphoantigen-responsive Vγ9Vα2-T cells could provide important advantages over DC with respect to clinical immunotherapeutic application, as Vγ9Vα2-T cells are more numerous compared to DC precursors, mature quickly (< 24 hr vs. 7-10 days for moDC) into professional APC, have better lymph node homing characteristics and a more uniform and consistent proinflammatory functional status. In order to assess whether Vγ9Vα2-T cells could be used as a novel Ag presenting platform for iNKT, we performed a phenotypic analysis of resting and phosphoAg-activated Vγ9Vα2-T cells and found that activation indeed resulted in an upregulation of Ag-presenting, co-stimulatory molecules and APC maturation markers. Importantly however, we found that the capacity of Vγ9Vα2-T to act as APC for iNKT cells did not result from de novo synthesis of relevant Ag presenting molecules by Vγ9Vα2-T cells, but was critically dependent on the presence of CD1d on phosphoantigen-expressing cells used for activation of Vγ9Vα2-T cells. Using lipophilic fluorochromes that are stably inserted into cellular membranes we could demonstrate a time-dependent and phosphoantigen-specific exchange of membrane patches between Vγ9Vα2-T cells and phosphoAg expressing cells with which the Vγ9Vα2-T cells interacted. This exchange of CD1d-containing membrane-fragments (termed trogocytosis) resulted in CD1d-expressing Vγ9Vα2-T cells that were subsequently able to activate iNKT cells in a CD1d-restricted and α-GalCer dependent fashion. We are currently performing fluorescent life-imaging techniques to provide direct evidence for trogocytosis. Furthermore, in preliminary experiments we have found that the acquisition of MHC-I restricted APC-functions by Vγ9Vα2-T cells also requires trogocytosis in order to stimulate CD8+ T cells. These findings provide evidence that apart from their known pro-inflammatory and cytolytic antitumor effector functions, Vγ9Vα2-T cells have a thus far unexplored important additional role within the tumor microenvironment by acting as APC propagating the presentation of tumor associated Ag to the immune system. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3533. doi:1538-7445.AM2012-3533