Fig. 1. Recently activated CD4 cells home to downstream LNs in vivo.

a Experimental setup to investigate lymphocyte migration through lymphatic vessels. Recipient B6 mice received OTII⁺ cells expressing the green-to-red photo-convertible fluorescent protein Dendra2 (D2) and were immunized with LPS-matured OVA-loaded DCs into the right foodpad. Five days later, the right pop LN was photo-converted by exposure to UV light (see also Supplementary Fig. 1). Representative FACS plots from the left non-photo-converted (green background) and right photo-converted (red background) pop LNs and from non-photo-converted (green background) downstream para-aortic and renal LNs analyzed 24 h after UV exposure. Plots are gated on D2, D2-OTII⁺, or D2-RED⁺OTII⁺ cells as indicated. b Frequency of D2-RED⁺OTII⁺ cells among all living cells and c absolute cell counts of D2-RED⁺OTII⁺ cells per LN (pop popliteal, para para-aortic, br brachial, m mesenteric, D2 Dendra2). Representative (a) or pooled (b, c) data of nine mice analyzed in three independent experiments.