Figure 1.

Selective CD28 blockade reverses lymphopenia-induced differentiation of memory CD4⁺ T cells in the lymph node. (A) Fully MHC-mismatched skin from BALB/c donors were grafted onto C57BL/6 recipients. Recipients were treated with or without 0.2mg anti-CD4 and 10μg anti-CD8 one day prior to transplant and with or without 100μg anti-CD28dAb on days 0, 2, 4, 6, and weekly thereafter. Mice were euthanized six weeks post-transplant and lymphoid cells from the blood, lymph node, spleen, bone marrow, kidney, liver, and lung were analyzed by flow cytometry. Immediately prior to euthanasia fluorescently labeled anti-CD4 and anti-CD8 antibody were administered IV to label circulating T cells. (B) Representative flow cytometry plots of CD4⁺ and CD8⁺ T cells on day 21 in the blood. (C) Frequency of CD4⁺ and CD8⁺ T cells in the blood over time. (D) Left, absolute count of CD4⁺ T cells per mL of blood over time. Right, absolute count of CD4⁺ T cells at day 21 and day 42. (E) Left, absolute count of CD8⁺ T cells per mL of blood over time. Right, absolute count of CD8⁺ T cells at day 21 and Day 42. (F) Proportion of CD44 expressing CD4⁺ and CD8⁺ T cells in the blood over time. (G) Proportion of CD44 expressing CD4⁺ and CD8⁺ T cells in the blood at day 21 and in the blood, spleen, and lymph node at day 42. Experiment shown is representative of 2 independent experiments with a total of 8-10 mice per group. *p < 0.05, **p < 0.01, ***p < 0.001, ****P < 0.0001 by one way ANOVA correcting for multiple comparisons.