Physiological inputs through β₂ARs are involved in lymphocyte recirculation. (A) Flow cytometric analysis of B cell distributions in mixed BM chimeras generated with 50% Adrb2^+/+ or Adrb2^−/− (CD45.2⁺), plus 50% WT (CD45.1⁺) cells. Data show percentages of CD45.2⁺ B cells (CD19⁺IgD^hiCD95⁻) in spleen, mesenteric LNs (mLNs), lymph, and blood. (B) Adrb2^+/− or Adrb2^−/− spleen cells were labeled with CFSE and transferred to WT mice. 2 d later, the recipient mice were treated with integrin-neutralizing antibodies for 14 h. Fractions of transferred lymphocytes remaining in mesenteric LNs were determined as ratios relative to those in mice that did not undergo integrin blockade. (C) Adrb2^+/− or Adrb2^−/− (CD45.2⁺) and WT (CD45.1⁺) spleen cells were labeled with CFSE, co-transferred to WT (CD45.2⁺) recipients and enumerated in mesenteric LNs 90 min after transfer. Normalized ratios of CD45.2⁺ cells relative to CD45.1⁺ cells were obtained by dividing observed ratios by the ratio of input populations. (D) Chemical depletion of adrenergic nerves was performed by i.p. injection of 6-OHDA into WT mice, and then mice were subjected to integrin blockade for 14 h. Fractions of lymphocytes remaining in mesenteric LNs were determined as ratios relative to those in vehicle- or 6-OHDA–treated mice that did not undergo integrin blockade. Data are representative of three experiments (A), or pooled from three (B) or two (C and D) experiments. Each symbol represents an individual mouse. Bars indicate means. **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; ns, not significant. P-values were obtained by one-way ANOVA with Bonferroni’s post-test (A) or unpaired Student’s t test (B–D).