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Many in vitro studies say yes. Back in the 1980s, Gideon Berke was one of the first to use video to track CTL (cytotoxic killer cells) killing target cells. He estimated one CTL was capable of killing 30 to 50 target cells serially. Since then, most studies use the same playbook, namely, in vitro suspension or cell pellet cultures of CTLs with their target cells. Such studies confirmed CTLs

  • Can kill multiple targets within a few minutes.
  • Can do this both serially as well as simultaneously.

Turns out CTL target killing capacity in vitro is higher than that in vivo. A Feb 2016 issue of Immunity has a paper from Reinhold Forster‘s lab where they used Two-photon excitation microscopy of explanted mouse lymph nodes to assess in vivo CTL killing of virus infected cells (In Vivo Killing Capacity of Cytotoxic T Cells Is Limited and Involves Dynamic Interactions and T Cell Cooperativity. Halle, S. et al. Immunity 44, 1–13, February 16, 2016. http://www.sciencedirect.com/sci…). This study finds

  • in vivo CTL target cell killing is much less efficient, killing an average of 2 to 16 virus-infected cells per day.
  • CTLs in vivo appear to cooperate with each other in killing their targets (see figure below).

Makes sense because in vivo CTLs have to navigate the complex topography of extracellular matrix and non-target cells in order to find their targets, engage and kill. However, need other studies to confirm these findings to be sure these are consistent features of CTL killing target cells in vivo.

Further reading:

Garcia, Victor, et al. “Estimating the in vivo killing efficacy of cytotoxic T lymphocytes across different Peptide-MHC complex densities.” PLoS Comput Biol 11.5 (2015): e1004178. http://www.ploscompbiol.org/arti…

Elemans, Marjet, et al. “Rates of CTL killing in persistent viral infection in vivo.” PLoS Comput Biol 10.4 (2014): e1003534. http://www.ploscompbiol.org/arti…

Elemans, Marjet, Nafisa-Katrin Seich Al Basatena, and Becca Asquith. “The efficiency of the human CD8+ T cell response: how should we quantify it, what determines it, and does it matter?.” PLOS Comput Biol 8.2 (2012): e1002381. http://www.ploscompbiol.org/arti…

Wiedemann, Aurelie, et al. “Cytotoxic T lymphocytes kill multiple targets simultaneously via spatiotemporal uncoupling of lytic and stimulatory synapses.” Proceedings of the National Academy of Sciences 103.29 (2006): 10985-10990. http://www.pnas.org/content/103/…

Stinchcombe, Jane C., et al. “The immunological synapse of CTL contains a secretory domain and membrane bridges.” Immunity 15.5 (2001): 751-761. http://ac.els-cdn.com/S107476130…