Figure 5. Kaede-red CD4⁺ T cells reenter the circulation from draining LNs.

(a) CCR7 and CD62L expression on CD4⁺ CD44^hi E-sel-Fc⁺ T cells within the blood of resting C57Bl/6 mice. Leukocytes recovered from the blood were gated on CD3⁺ CD4⁺ CD44^hi memory T cells and on CD3⁺ CD4⁺ CD44^lo-int naïve T cells (top left panel). The CD44^hi T cell population was then gated on E-sel-Fc⁺ cells (top right panel). Middle and bottom histograms depict CCR7 and CD62L expression on CD4⁺ CD44^lo-int naïve T cells, CD4⁺ CD44^hi bulk memory T cells, and on CD4⁺ CD44^hi E-sel-Fc⁺ memory T cells. Each plot is from 6 mice pooled and is representative of 3 independent experiments. Graphs depict the average percent of each CD3⁺ CD4⁺ T cell population in the blood that express CCR7 or CD62L. Black bars depict the percent of CD3⁺ CD4⁺ T cells that express intermediate CCR7 or CD62L and white bars show the percent of CD3⁺ CD4⁺ T cells that express high CCR7 or CD62L. (b) Shaved abdominal skin of Kaede transgenic mice was exposed to 420 nm light for 5 minutes on 3 consecutive days. Flow cytometric analysis of Kaede-green and Kaede-red expression on CD3⁺ CD4⁺ T cells recovered from the blood, non-draining cervical LNs and draining axillary LNs 48 h after the final photoconversion. Data are representative of 3 experiments with 8 mice/group total. (c) The right ear of Kaede transgenic mice was injected with 10 μL of a 1:1 PBS:CFA emulsion, and then the shaved abdominal skin was photoconverted as in (a). Flow cytometry plots depict Kaede-green and Kaede-red expression by CD3⁺ CD4⁺ T cells recovered from the CFA-injected distal ear skin 48 h after the final photoconversion. Numbers in plots are average percent Kaede-red T cells of CD3⁺ CD4⁺ T cells recovered from the ear, and are calculated from 3 experiments with 8-14 mice total/group. Data shown are of 6 mice pooled/group.