Fig. 5: Ineffective T cell activation and in vivo immunity in the absence of CD99.

a, b Comparison of in vitro activation of CD8⁺ T cells from WT and Cd99^−/− mice. Flow cytometry profiles of CFSE dilution (n = 5 mice per group) (a) and the expression of CD69, CD25, and CD44 (n = 5 mice per group) (b) by anti-CD3/CD28 stimulated WT and Cd99^−/− T cells. Plots of the proportions (%) of T cells in each diluted CFSE peak (a) and marker-positive cells (b). Data a, b are pooled from two independent experiments (n = 2–3 mice/group/experiment). c In vivo activation of WT and Cd99^−/− J15 CD8⁺ T cells. Flow cytometry profiles of female Thy1.2⁺ WT or Cd99^−/− J15 CD8⁺ T cells in the spleens of adoptive hosts (Thy1.1⁺). The numbers of CD8⁺Thy1.2⁺ cells in the spleen on days 3 and 7 post-immunization are plotted (n = 7 mice per group) using data pooled from three independent experiments (n = 2–3 mice/group/experiment). d Comparison of allograft-rejection between female WT and Cd99^−/− B6 recipients. Representative images of male BALB.B tail-skin (red arrow) rejected (dotted line) or surviving (solid line), and syngeneic B6 tail-skin (black arrow) on the tail of a WT or Cd99^−/− B6 recipient on day 14 post-transplantation. Kaplan-Meier survival plot of the grafts, with median survival time (MST) shown in parentheses. Flow cytometric profiles of H60-tetramer- or H4-tetramer-binding CD11a⁺ CD8 T cells in blood on day 12 post-transplantation. Plots of the percentage of tetramer-binding cells in blood CD8 T cells. Data represent two independent experiments (n = 9 mice/group/experiment). e B16F10-OVA tumor growth in B6 mice to which were transferred naive CD45.1⁺ WT or Cd99^−/− OT-I CD8 T cells. Tumor sizes and percentages of OVA-tetramer-binding CD45.1⁺ cells in blood CD8 T cells are plotted. Representative flow cytometric profiles of OVA-tetramer-binding CD45.1⁺ CD8 T cells on day 10 post-transfer. Data represent two independent experiments (n = 5 mice/group/experiment). Data a–e are shown as mean ± SEM. Statistical significance was assessed using unpaired two-tailed t-test (a–e), and log-rank (Mantel-Cox) test (d graft survival). Exact p-values are presented in the figure. Source data are provided as a Source Data file.