CCR7 expression is crucial for lymphoma cell homing to SLOs and lymphomagenesis. (A) Surface expression of maturation/differentiation markers, chemokine receptors, and adhesion molecules on B220⁺ gated tumor cells derived from LNs of lymphomatous Wt Eμ-Myc or CCR7^−/− Eμ-Myc transgenic mice was assessed by flow cytometry (n = 4-7 mice per marker; isotype control; shaded curve). (B) Quantitative RT-PCR of chemokine and LT transcripts in tumor cells of Wt Eμ-Myc (n = 3 or 4) or of CCR7^−/− Eμ-Myc (n = 3) transgenic mice. Transcript expression was normalized to glyceraldehyde-3-phosphate dehydrogenase. (C) Chemotaxis of tumor cells derived from Wt Eμ-Myc transgenic mice or from CCR7^−/− Eμ-Myc transgenic mice toward CCL21 (100nM) and CXCL12 (25nM). Error bars represent SD for 3 or 4 independent experiments with triplicates per each group. *P ≤ .05; **P ≤ .01. (D) Tumor-free survival of mice that received 1 × 10⁵ tumor cells derived from Wt Eμ-Myc transgenic mice or from CCR7^−/− Eμ-Myc transgenic mice. Pooled data of 3 independent experiments are shown (n = 5-8 mice per group in each independent experiment. (E) Infiltration of Wt Eμ-Myc compared with CCR7^−/− Eμ-Myc tumor cells into peripheral blood (PBL), spleen, and LNs of recipient congenic Wt mice on day 6, and tumor cell infiltration into PBL, spleen, LN, bone marrow (BM), and thymus of recipient congenic Wt mice on days 11 to 14 was quantitated by flow cytometry analysis after intravenously tumor cell application. Percentage of infiltrating tumor cells per organ was determined by gating on B220⁺/CD45.2⁺ double-positive cells (n = 4 mice per group on day 6; n = 5-14 mice (PBL, spleen, and LN) and n = 3-5 mice (BM, thymus) per group on days 11 to 14. *P ≤ .05; **P ≤ .01.