Figure 2.

Peripheral lymph node (LN) cellularity is restricted in both adult and old heterochronic parabionts. (A) Data depict numbers and distribution of stromal (Ter119⁻ CD45⁻ CD35/21⁺) cell subsets within cervical LN in nonsurgical controls (NS) (right), and parabiosed mice (left) adult isochronic parabiosis, heterochronic parabiosis, and in old isochronic parabiosis. Shown are numbers of gp38⁻CD31⁻ double-negative (DN, open parts of the bar), gp38⁺CD31⁻ fibroblastic reticular cells (FRC, closed bar parts), gp38⁻CD31⁻ lymphoid endothelial cells (LEC, dark gray), and gp38-CD31+ blood endothelial cells (BEC, light gray). (B) Number of adult or old CD3 T cells (derived from total cell counts and CD3 flow cytometric staining) in nonsurgical control, isochronic parabionts, and heterochronic parabionts from pooled peripheral lymph nodes (LNs; brachial, inguinal, and popliteal) contralateral to the side of surgery. Open bars indicate cell numbers originating from old mice (always CD45.2), gray bars indicate cell numbers originating from adult CD45.1 mice, and black bars indicate cell numbers from adult wildtype (CD45.2) mice. n = 8–16 mice, pooled from two to three experiments. (C) Numbers of adult or old CD8 T cells in nonsurgical control, isochronic parabionts, and heterochronic parabionts in peripheral LN, from mice analyzed in panel B. (D) Numbers of adult or old CD4 T cells in nonsurgical control, isochronic parabionts, and heterochronic parabionts in peripheral LN, from mice analyzed in panel B. (E) Adult and old LN CD4 and CD8 T cell subset numbers following heterochronic parabiosis and separation surgery (contralateral brachial and inguinal LN shown); analysis was done as in panels B-D, on n = 5 animals/age group. Significance was determined by Mann–Whitney U-test for adult and old nonsurgical controls, whereas significance for parabionts was determined by two-way ANOVA with Sidak’s post-test. Statistical significance: *p < .05, ** p < .01, *** p < .001, **** p < .0001, and ns is not significant.