title: Cellular immune responses towards regulatory cells.
abstract: This thesis describes the results from two published papers identifying spontaneous cellular immune responses against the transcription factors Foxp3 and Foxo3. The tumor microenvironment is infiltrated by cells that hinder effective tumor immunity from developing. Two of these cell types, which have been linked to a bad prognosis for patients, are regulatory T cells (Treg) and tolerogenic dendritic cells (DC). Tregs inhibit effector T cells from attacking the tumor through various mechanisms, including secreted factors and cell-to-cell contact. Tregs express the transcription factor Foxp3, which is necessary for their development and suppressive activities. Tolerogenic DCs participate in creating an environment in the tumor where effector T cells become tolerant towards the tumor instead of attacking it. The transcription factor Foxo3 was recently described to be highly expressed by tolerogenic DCs and to programme their tolerogenic influence. This thesis describes for the first time the existence of spontaneous cellular immune responses against peptides derived from Foxp3 and Foxo3. We have detected the presence of cytotoxic T cells that recognise these peptides in an HLA-A2 restricted manner in cancer patients and for Foxp3 in healthy donors as well. In addition, we have demonstrated that the Foxp3- and Foxo3-specific CTLs recognize Foxp3- and Foxo3-expressing cancer cell lines and importantly, suppressive immune cells, namely Tregs and in vitro generated DCs. Cancer immunotherapy is recently emerging as an important treatment modality improving the survival of selected patients. The current progress is largely owing to targeting of the immune suppressive milieu that is dominating the tumor microenvironment. This is being done through immune checkpoint blockade with CTLA-4 and PD-1/PD-L1 antibodies and through lymphodepleting conditioning of patients and ex vivo activation of TILs in adoptive cell transfer. Several strategies are being explored for depletion of Tregs and for modulation of Treg and DC suppressive activity, including CD25 antibodies and chemotherapy. The research presented in this thesis offer an alternative approach to targeting suppressive cells subsets, by activating the immune system against proteins expressed by these cell types.
authors.affiliation: stinekiaer@gmail.com.
authors.forename: Stine Kiær
authors.initials: SK
authors.lastname: Larsen
mesh_terms: D006801:Humans; D007111:Immunity, Cellular; D007158:Immunologic Techniques; D007167:Immunotherapy / Q000379:methods*; D009369:Neoplasms / Q000276:immunology / Q000628:therapy; D050378:T-Lymphocytes, Regulatory / Q000502:physiology*; D059016:Tumor Microenvironment / Q000276:immunology