β₂AR stimulation inhibits lymphocyte egress from LNs. (A) Experimental design for β₂AR agonist administration and integrin blockade. During continuous administration of saline or β₂AR agonists, WT mice were treated with neutralizing antibodies against α4 and αL integrins for 22 h. Fractions of lymphocytes remaining in LNs after integrin blockade were determined as ratios relative to those in saline-treated mice that did not undergo integrin blockade. (B) Fractions of CD4⁺ T cells (CD4⁺) and B cells (CD19⁺IgD^hiCD95⁻) remaining in mesenteric LNs were determined upon treatment with saline or the indicated doses of clenbuterol or salbutamol. Data are shown as mean ± SEM for at least three mice. (C) CD45.1⁺ WT spleen cells were transferred to CD45.2⁺ WT mice that had been treated with saline, clenbuterol (0.4 mg/kg), or salbutamol (12 mg/kg) and enumerated in mesenteric LNs 90 min after transfer. Data are shown as the number of CD4⁺ T cells (CD4⁺) or B cells (CD19⁺) recovered in each recipient per 10⁶ transferred CD45.1⁺ populations. (D and E) BM chimeras generated using WT or Adrb2^−/− mice as donors (D) or recipients (E) were treated as in A. The remaining fraction of B cells (CD19⁺IgD^hiCD95⁻) is shown for each. Each symbol represents an individual mouse and bars indicate means (C–E). Data are pooled from two (B and E) or three (C and D) experiments. Sal, saline; Clen, clenbuterol; Salb, salbutamol. **, P < 0.01; ns, not significant. P-values were obtained by one-way ANOVA with Bonferroni’s post-test (C) or unpaired Student’s t test (D and E).