In Vivo Killing Capacity of Cytotoxic T Cells Is Limited and Involves Dynamic Interactions and T Cell Cooperativity

• Published in: Immunity (Cambridge, Mass.) Vol. 44; no. 2; pp. 233 - 245
• Main Authors: Halle, Stephan, Keyser, Kirsten Anja, Stahl, Felix Rolf, Busche, Andreas, Marquardt, Anja, Zheng, Xiang, Galla, Melanie, Heissmeyer, Vigo, Heller, Katrin, Boelter, Jasmin, Wagner, Karen, Bischoff, Yvonne, Martens, Rieke, Braun, Asolina, Werth, Kathrin, Uvarovskii, Alexey, Kempf, Harald, Meyer-Hermann, Michael, Arens, Ramon, Kremer, Melanie, Sutter, Gerd, Messerle, Martin, Förster, Reinhold
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 16.02.2016; Elsevier Limited; Cell Press
• Subjects: Animals; Antigens; Apoptosis; Calcium Signaling; Cell Communication; Cells, Cultured; Confidence intervals; Cytokines; Cytotoxicity; Cytotoxicity, Immunologic; Experiments; Fibroblasts; Herpesviridae Infections - immunology; Humans; Immune Evasion; Infections; Lymphatic system; Lymphocytes; Mathematical models; Mice; Mice, Inbred C57BL; Mice, Knockout; Microscopy; Microscopy, Fluorescence, Multiphoton; Muromegalovirus - immunology; Perforin - genetics; Perforin - metabolism; Rodents; Statistical analysis; T cell receptors; T-Lymphocyte Subsets - immunology; T-Lymphocyte Subsets - virology; T-Lymphocytes, Cytotoxic - immunology; T-Lymphocytes, Cytotoxic - virology; Vaccinia - immunology; Vaccinia virus - immunology; Viral infections; Viruses
• ISSN: 1074-7613; 1097-4180
• DOI: 10.1016/j.immuni.2016.01.010

According to in vitro assays, T cells are thought to kill rapidly and efficiently, but the efficacy and dynamics of cytotoxic T lymphocyte (CTL)-mediated killing of virus-infected cells in vivo remains elusive. We used two-photon microscopy to quantify CTL-mediated killing in mice infected with herpesviruses or poxviruses. On average, one CTL killed 2–16 virus-infected cells per day as determined by real-time imaging and by mathematical modeling. In contrast, upon virus-induced MHC class I downmodulation, CTLs failed to destroy their targets. During killing, CTLs remained migratory and formed motile kinapses rather than static synapses with targets. Viruses encoding the calcium sensor GCaMP6s revealed strong heterogeneity in individual CTL functional capacity. Furthermore, the probability of death of infected cells increased for those contacted by more than two CTLs, indicative of CTL cooperation. Thus, direct visualization of CTLs during killing of virus-infected cells reveals crucial parameters of CD8+ T cell immunity. [Display omitted] •Two-photon imaging indicates that CTLs kill 2–16 virus-infected cells per day•CTLs form kinapses rather than stable synapses when killing virus-infected cells•Some CTL contacts trigger long-lasting calcium fluxes in virus-infected cells•CTLs can cooperate during killing of virus-infected cells According to in vitro assays, T cells are thought to kill rapidly and efficiently. Using two-photon microscopy, Forster and colleagues have found that killing capacities of single cytotoxic T lymphocytes (CTLs) in vivo are heterogeneous and limited. Quantification of target-cell-death probabilities identified efficient cooperative killing when multiple CTLs attacked a virus-infected cell.