Apoptosis paves the detour path for CD8 T cell activation against intracellular bacteria

Cell Microbiol. 2004 Jul;6(7):599-607. doi: 10.1111/j.1462-5822.2004.00408.x.

Abstract

Intracellular bacteria such as Mycobacterium tuberculosis primarily infect macrophages. Within these host cells, the pathogens are confined to phagosomes and their antigens are secluded from the classical MHC I presentation pathway. Moreover, macrophages fail to express certain antigen presenting molecules like CD1 proteins. As a result of this intracellular lifestyle, the pathways for the induction of MHC I- and CD1-restricted CD8 T cells by such microorganisms remain elusive. Based on recent findings in tuberculosis and salmonellosis, we propose a new detour pathway for CD8 T cell activation against intracellular bacteria through apoptotic blebs from infected macrophages. Pathogen-derived antigens including proteins and lipids are delivered from infected cells to non-infected dendritic cells. Subsequently, these professional antigen presenting cells display microbial antigens through MHC I and CD1 to T cells. Thus, cross-priming mediated by apoptotic vesicles is not just a matter of antigen distribution, but an intrinsic immunological function due to the nature of phagosomally located intracellular bacteria. We consider infection-induced apoptosis the conditio sine qua non for antigen-specific CD8 T cell activation by phagosome-enclosed pathogens. This important new function of cell death in antibacterial immunity requires consideration for rational vaccine design.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Apoptosis*
  • CD8-Positive T-Lymphocytes / immunology*
  • Humans
  • Lymphocyte Activation / immunology*
  • Macrophages / microbiology*
  • Mycobacterium tuberculosis / immunology*
  • Salmonella / immunology*
  • Salmonella Infections / microbiology
  • Tuberculosis / microbiology