To study in vivo CD8 T cell differentiation, we quantified the coexpression of multiple genes in single cells throughout immune responses. After in vitro activation, CD8 T cells rapidly express effector molecules and cease their expression when the antigen is removed. Gene behavior after in vivo activation, in contrast, was quite heterogeneous. Different mRNAs were induced at very different time points of the response, were transcribed during different time periods, and could decline or persist independently of the antigen load. Consequently, distinct gene coexpression patterns/different cell types were generated at the various phases of the immune responses. During primary stimulation, inflammatory molecules were induced and down-regulated shortly after activation, generating early cells that only mediated inflammation. Cytotoxic T cells were generated at the peak of the primary response, when individual cells simultaneously expressed multiple killer molecules, whereas memory cells lost killer capacity because they no longer coexpressed killer genes. Surprisingly, during secondary responses gene transcription became permanent. Secondary cells recovered after antigen elimination were more efficient killers than cytotoxic T cells present at the peak of the primary response. Thus, primary responses produced two transient effector types. However, after boosting, CD8 T cells differentiate into long-lived killer cells that persist in vivo in the absence of antigen.
CD8 single-cell gene coexpression reveals three different effector types present at distinct phases of the immune response
Abbreviations used: LCMV, lymphocytic choriomeningitis virus; PE, primary early; PL, primary plateau; PM, primary memory; PP, primary peak; SCD8, secondary response CD8; SM, secondary memory; Tc, T-cytotoxic; Tg, transgenic.
A. Peixoto and C. Evaristo contributed equally to this paper.
A. Peixoto's present address is CBR Institute for Biomedical Research and Department of Pathology, Harvard Medical School, Boston, MA 02115.
H. Veiga-Fernandes's present address is Division of Molecular Immunology, National Institute for Medical Research, London NW7 1AA, England, UK.
António Peixoto, César Evaristo, Ivana Munitic, Marta Monteiro, Alain Charbit, Benedita Rocha, Henrique Veiga-Fernandes; CD8 single-cell gene coexpression reveals three different effector types present at distinct phases of the immune response . J Exp Med 14 May 2007; 204 (5): 1193–1205. doi: https://doi.org/10.1084/jem.20062349
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