No life without death--apoptosis as prerequisite for T cell activation.
Winau, F;
Hegasy, G;
Kaufmann, SHE;
Schaible, UE;
(2005)
No life without death--apoptosis as prerequisite for T cell activation.
Apoptosis, 10 (4).
pp. 707-715.
ISSN 1360-8185
DOI: https://doi.org/10.1007/s10495-005-2940-6
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The orchestrated death of infected cells is key to our understanding of CD8 T cell activation against pathogens. Most intracellular bacteria including Mycobacterium tuberculosis, the etiologic agent of tuberculosis, remain enclosed in phagosomes of infected macrophages. CD8 T cells play a critical role in defense of infection and recognize antigens originating from the cytosol presented by MHC-I molecules. Since mycobacteria do not gain access to the cytosolic MHC-I presentation pathway, the fundamental question as to how CD8 T cells encounter mycobacterial antigens remains to be solved. In this review, we focus on solutions for this enigma and describe the detour pathway of T cell activation. Mycobacteria induce cell death of infected macrophages which thereby leave a last message by releasing apoptotic vesicles. Subsequently, these antigen-containing entities are engulfed by dendritic cells which process the mycobacterial cargo for efficient antigen presentation and CD8 T cell activation. Since the dying infected cell is the origin of a protective T cell response destined to preserve life and individuality, the detour pathway represents an altruistic principle at a cellular level which corresponds to the macroscopic world where death is the precondition to perpetuate the living.