Final Report Summary - CD8 T CELLS (Development and differentiation of CD8 T lymphocytes)
This project had two main related objectives- #1: that of providing better strategies to ensure the rapid reconstitution of the peripheral and the gut T cell compartments, and #2 that of comparing immune responses and determine the conditions to obtain efficient memory generation. The first objective was fully accomplished. We did identify the thymus T cell populations that generate the gut intra-epithelial T cells (Nature Mucosal Immunology 4, 93-101, recommended reading, PubMed), and demonstrated that thymus transplants may be used to rapidly reconstitute the peripheral T cell pool (J. Exp. Med. 209: 1401-1408. See Journal Cover; See Mini-review on this article by Thomas Boehm in the same number -pages 1397-1400; See Nature Reviews Highlights. Recommended reading Faculty of 1, 000). This later Ms. changed the current dogma, that thymocytes were short-lived and the required continuous renewal from precursors present in the BM. We determined that in the absence of bone-marrow precursors the thymus populations self-renewed, reconstituting a fully normal peripheral T cell pool. These data raise the possibility that thymus transplants can be used to reconstitute the peripheral T cell pools, with major advantages over the transplantation of the bone-marrow, what should have major impact in the therapy of T cell deficiency. Lastly, we also described the cartography of gene expression in early thymocytes. This extensive data questions several of the main concepts on early thymocyte differentiation (published in PLoS1).
With relation to Objective 2, we studied the role of clonal dominance in CD8 differentiation (J. Virology), and characterized in detail an new population of effector T cells that we dominated “inflammatory effectors” These cells are induced immediately after activation, secrete a major burst of inflammatory cytokines and chemokines, and have a major capacity to recruit T and accessory cell types to the site where they were present (Frontiers in Immunology). We showed that 56 of these cells injected into a lymph-node could recruit up to 107 cells in 24h. These cells also induced the local up-regulation of S1P, preventing T cells to leave the organ, what promotes the interactions between antigen-specific T cells and dendritic cells presenting the Ag (Ag+DC). We developed a model allowing the visualization by 2P intra-vital microscopy of the T/ Ag+DC interactions. These interactions were visualized for the first time by in vivo imaging. They show that in contrast to CD4 T cells, which make initial short T/DC contacts. CD8 T cells form immediate stable T/ Ag+DC complexes. Moreover, upon Ag+DC binding CD8 T cells acquire DC membranes at the cell surface by trogocytosis, present Ag directly to CD4 T cells, recruit them by direct contact to Ag+DC binding and are able to induce their extensive division. Lastly, the presence of CD8 potentiates CD4 responses leading to their precocious expression of activation markers, chemokines and cytokines.
Therefore, in contrast to current believes, CD4 and CD8 interact directly, and modulate the respective functions (in preparation). Lastly, we determined the importance of DNA repair in lymphocyte accumulation during immune responses. We described that CD8 T cells developed unique mechanisms of DNA repair which allow their survival during division, guaranteeing DNA integrity, i.e. preventing transformation (submitted). We found that “in vitro” and “in vivo” read-outs did not reveal the same functions, and how TCR-down modulation prevented the visualization of endogenous antigen-specific cells during immune responses (submitted).
With relation to Objective 2, we studied the role of clonal dominance in CD8 differentiation (J. Virology), and characterized in detail an new population of effector T cells that we dominated “inflammatory effectors” These cells are induced immediately after activation, secrete a major burst of inflammatory cytokines and chemokines, and have a major capacity to recruit T and accessory cell types to the site where they were present (Frontiers in Immunology). We showed that 56 of these cells injected into a lymph-node could recruit up to 107 cells in 24h. These cells also induced the local up-regulation of S1P, preventing T cells to leave the organ, what promotes the interactions between antigen-specific T cells and dendritic cells presenting the Ag (Ag+DC). We developed a model allowing the visualization by 2P intra-vital microscopy of the T/ Ag+DC interactions. These interactions were visualized for the first time by in vivo imaging. They show that in contrast to CD4 T cells, which make initial short T/DC contacts. CD8 T cells form immediate stable T/ Ag+DC complexes. Moreover, upon Ag+DC binding CD8 T cells acquire DC membranes at the cell surface by trogocytosis, present Ag directly to CD4 T cells, recruit them by direct contact to Ag+DC binding and are able to induce their extensive division. Lastly, the presence of CD8 potentiates CD4 responses leading to their precocious expression of activation markers, chemokines and cytokines.
Therefore, in contrast to current believes, CD4 and CD8 interact directly, and modulate the respective functions (in preparation). Lastly, we determined the importance of DNA repair in lymphocyte accumulation during immune responses. We described that CD8 T cells developed unique mechanisms of DNA repair which allow their survival during division, guaranteeing DNA integrity, i.e. preventing transformation (submitted). We found that “in vitro” and “in vivo” read-outs did not reveal the same functions, and how TCR-down modulation prevented the visualization of endogenous antigen-specific cells during immune responses (submitted).