Article Figures & Data
Figures
- FIGURE 1.
Schematic of TRM homeostasis model. Cells are recruited at a constant rate r, self-renew through division at rate p, and are lost at rate d, leading to exponentially distributed residence times within the tissue. Extensions of this model include different residence time distributions or decomposing the decay rate into distinct terms for cell death and tissue egress (107).
- FIGURE 2.
Impact of heterogeneity on population dynamics. (A) Assuming precursor input is negligible, homogeneity in the net loss rate across the population leads to a single exponential decay function (Eq. 2). (B) Conversely, if there is heterogeneity in net loss among cell subsets (e.g., because of different death rates), then the observed decay (dashed line) reflects the sum of the decay kinetics of each subset (red and blue lines).
- FIGURE 3.
Mathematical analysis of published TRM data. Eq. 2 fitted to data from (66) (A) and (67) (B). Solid lines are the model predictions, points are the data, and gray shaded regions are prediction envelopes obtained by sampling parameters from their 95% confidence intervals. Least-squares optimization was performed on the log-scale and residuals were normally distributed (using the Shapiro–Wilk test), except those for the nasal tissues (NT). The NT fits are thus included for approximate comparison only. Note that we use the above approach to illustrate how a simple model can be applied to experimental data. In a more thorough analysis, these predictions would then be compared with those from alternative models to identify the most parsimonious description of the data. Code for the above analysis can be found at https://github.com/SineadMorris/TRMecology.
Tables
- Table I. Experimental estimates of CD8+ TRM population parameters in different murine tissues and infection settings
Tissue System Time Detectable (d) Population t1/2a Self-Renewal References Lungs Influenza <210 5–7 d No BrdU uptake detected (7, 67, 77) Liver Malaria >100 28–36 d (11, 68) LCMV >120 (17) FRT HSV >80 (5, 35) LCMV >120 (17) Intestine Yersinia pseudotuberculosis >120 (16) LCMV >120 (17) Brain VACV >120 <1% BrdU+ in 1 wk (74) LCMV >240 9% Ki67+ (12) Skin VACV >160 (6) LCMV >200 (67) HSV >540 <5% BrdU+ in 1 wk (3, 4, 56, 81) Time detectable represents the maximum observed duration of TRM persistence; tissues are approximately arranged in order of increasing estimates.
↵a t1/2 estimates do not account for any ongoing recruitment from circulating subsets.
LCMV, lymphocytic choriomeningitis; VACV, vaccinia virus.
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