tLN supports lymphocyte recirculation. Three to 4 weeks after syngenic LN engraftment to C57BL/6 ear pinnae, tLNs and control LNs were harvested for sectioning and immunofluorescent staining. Control LNs and tLNs were compared for expression of the vascular endothelial cell marker (A) VCAM-1 (green) and (B) the chemokine CCL21 (green). Sections were also stained for CD4⁺ cells (blue) and IgM⁺ B cells (red). Images shown are representative of 3 replicate mice. To confirm recirculation, CD45.1 LNs were engrafted on CD45.2 recipients, and expression of CD45.1 and CD45.2 by control and tLN cells was assessed by flow cytometry. Scale bars denote 50 μm. (C) Representative flow cytometric plots show levels of CD45.1 and CD45.2 for both control and tLN.