title: CD8 T cell memory recall is enhanced by novel direct interactions with CD4 T cells enabled by MHC class II transferred from APCs.
abstract: Protection against many intracellular pathogens is provided by CD8 T cells, which are thought to need CD4 T cell help to develop into effective memory CD8 T cells. Because murine CD8 T cells do not transcribe MHC class II (MHC-II) genes, several models have proposed antigen presenting cells (APCs) as intermediaries required for CD4 T cells to deliver their help to CD8 T cells. Here, we demonstrate the presence of MHC-II molecules on activated murine CD8 T cells in vitro as well as in vivo. These MHC-II molecules are acquired via trogocytosis by CD8 T cells from their activating APCs, particularly CD11c positive dendritic cells (DCs). Transferred MHC-II molecules on activated murine CD8 T cells were functionally competent in stimulating specific indicator CD4 T cells. CD8 T cells that were "helped" in vitro and subsequently allowed to rest in vivo showed enhanced recall responses upon challenge compared to "helpless" CD8 T cells; in contrast, no differences were seen upon immediate challenge. These data indicate that direct CD8:CD4 T cell interactions may significantly contribute to help for CD8 T cells. Furthermore, this mechanism may enable CD8 T cells to communicate with different subsets of interacting CD4 T cells that could modulate immune responses.
authors: Department of Microbiology and Immunology, Yerkes National Primate Research Center and Emory University School of Medicine, Atlanta, Georgia, United States.
authors: Pablo A
authors: PA
authors: Romagnoli
authors: Mary F
authors: MF
authors: Premenko-Lanier
authors: Gilbert D
authors: GD
authors: Loria
authors: John D
authors: JD
authors: Altman
mesh_terms: D000818:Animals; D017951:Antigen Presentation / Q000276:immunology; D000938:Antigen-Presenting Cells / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002450:Cell Communication / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D007156:Immunologic Memory; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice
chemical_list: D000949:Histocompatibility Antigens Class II