Hanges During CTL Target Cell KillingFigure 3. LCI tracks target cell death during T cell mediated cytotoxicity. (A ) Images of a single cytotoxic event occurring immediately after the 10781694 start of imaging (t = 0 is approximately 30 min after plating CTLs onto target cells), (A ) intensity images at t = 0 and 5 h of imaging demonstrating CTL mediated target cell killing. Yellow boxes in (A) and (C), indicate the subregion in images (B) and (D). Arrows in (B) and (D) indicate the target cell tracked by mass profiling in (E ). (E) LCI mass profile of selected target cell after initiation of persistent contact with a target cell at the start of imaging. (F ) LCI mass profile of dying target cell. (I) Measured total mass vs. time for target cell shown in (E ). (J) Normalized mass of killed and healthy target cells over time. Normalized mass is mass divided by initial mass. Healthy cells show roughly 15 increase in normalized mass over 4 h (blue line indicates mean of n = 311 healthy M202 cells, grey region indicates +/2 SD). Killed target cells (red lines) show a decrease in mass of 20 to 60 over 1? h. (K) intensity image of stage location shown in (A) and (C) after 18 h of imaging, showing nearly complete death of target cells. (L) Intensity image of stage after 18 h of imaging M202 cells plated with untransduced (F5-) CD8+ T 16985061 cells showing viability of target cells plated with nonspecific T cells. (M) Normalized mass vs. time for n = 2058 healthy M202 cells treated with untransduced, control CTLs, showing roughly 15 increase in mass over 4 h. doi:10.1371/journal.pone.0068916.gD). Cytotoxic events are detectable despite the presence of nonspecific or unresponsive T cells within the broader population. LCI provides quantitative maps of the mass distribution within target cells during T cell mediated cytotoxic events (Figure 3E ). These mass distributions from successive image frames can be integrated to yield measurements of target cell mass over time (Equation 1 and Figure 3I). Individual cytotoxic events due to recognition of CTLs are confirmed by a characteristic decrease in target cell mass following prolonged contact (30 min to 2 h) with a corresponding CTL (Figure 3I and Movie S1). Target cell mass decreased by 20 to 60 over a period of 1? h when successfully attacked by a CTL, as compared to an increase in total target cell mass of 15 over 4 h when not killed by CTLs (Figure 3I ). Despite contact between T cells and target cells, there was no response in control experiments using HLAmismatched, antigen Title Loaded From File irrelevant target cells (lacking MART1) or non-specific T cells (Figure 3 K , Figure S1C and Figure S3C ). This indicates that target cell death was due to the presence of antigen-specific CTLs and that the rate and extent of target cell mass decrease due to T cell mediated cytotoxicity is directly quantifiable using LCI. T cell mediated cytotoxicity is evident within the first 30 min and confirmed within the first 2?4 h following the Title Loaded From File addition of CTLs, indicating the speed of the LCI approach in measuring T cell mediated cytotoxicity (Movie S1). An estimated 95 of target cells were dead by 18 h after the addition of CTLs, while greater than 95 of control target cells appeared healthy at 18 h (Figure 3 K and Figure S3).Mass Changes During CTL Target Cell KillingFigure 4. LCI measures CTL mass and mass accumulation rate during T cell mediated cytotoxicity. (A). Mass versus time of an activated CTL and corresponding target cell. t = 0.Hanges During CTL Target Cell KillingFigure 3. LCI tracks target cell death during T cell mediated cytotoxicity. (A ) Images of a single cytotoxic event occurring immediately after the 10781694 start of imaging (t = 0 is approximately 30 min after plating CTLs onto target cells), (A ) intensity images at t = 0 and 5 h of imaging demonstrating CTL mediated target cell killing. Yellow boxes in (A) and (C), indicate the subregion in images (B) and (D). Arrows in (B) and (D) indicate the target cell tracked by mass profiling in (E ). (E) LCI mass profile of selected target cell after initiation of persistent contact with a target cell at the start of imaging. (F ) LCI mass profile of dying target cell. (I) Measured total mass vs. time for target cell shown in (E ). (J) Normalized mass of killed and healthy target cells over time. Normalized mass is mass divided by initial mass. Healthy cells show roughly 15 increase in normalized mass over 4 h (blue line indicates mean of n = 311 healthy M202 cells, grey region indicates +/2 SD). Killed target cells (red lines) show a decrease in mass of 20 to 60 over 1? h. (K) intensity image of stage location shown in (A) and (C) after 18 h of imaging, showing nearly complete death of target cells. (L) Intensity image of stage after 18 h of imaging M202 cells plated with untransduced (F5-) CD8+ T 16985061 cells showing viability of target cells plated with nonspecific T cells. (M) Normalized mass vs. time for n = 2058 healthy M202 cells treated with untransduced, control CTLs, showing roughly 15 increase in mass over 4 h. doi:10.1371/journal.pone.0068916.gD). Cytotoxic events are detectable despite the presence of nonspecific or unresponsive T cells within the broader population. LCI provides quantitative maps of the mass distribution within target cells during T cell mediated cytotoxic events (Figure 3E ). These mass distributions from successive image frames can be integrated to yield measurements of target cell mass over time (Equation 1 and Figure 3I). Individual cytotoxic events due to recognition of CTLs are confirmed by a characteristic decrease in target cell mass following prolonged contact (30 min to 2 h) with a corresponding CTL (Figure 3I and Movie S1). Target cell mass decreased by 20 to 60 over a period of 1? h when successfully attacked by a CTL, as compared to an increase in total target cell mass of 15 over 4 h when not killed by CTLs (Figure 3I ). Despite contact between T cells and target cells, there was no response in control experiments using HLAmismatched, antigen irrelevant target cells (lacking MART1) or non-specific T cells (Figure 3 K , Figure S1C and Figure S3C ). This indicates that target cell death was due to the presence of antigen-specific CTLs and that the rate and extent of target cell mass decrease due to T cell mediated cytotoxicity is directly quantifiable using LCI. T cell mediated cytotoxicity is evident within the first 30 min and confirmed within the first 2?4 h following the addition of CTLs, indicating the speed of the LCI approach in measuring T cell mediated cytotoxicity (Movie S1). An estimated 95 of target cells were dead by 18 h after the addition of CTLs, while greater than 95 of control target cells appeared healthy at 18 h (Figure 3 K and Figure S3).Mass Changes During CTL Target Cell KillingFigure 4. LCI measures CTL mass and mass accumulation rate during T cell mediated cytotoxicity. (A). Mass versus time of an activated CTL and corresponding target cell. t = 0.
