CD8⁺Tregs and CD4⁺Tregs have similar transcriptional profiles. Lethally irradiated (900 cGy) Balb/c mice were transplanted with B6 Rag-1 BM (5 × 10⁶) and flow-sorted CD4⁺ Foxp3⁻ (0.4 × 10⁶) and CD8⁺ Foxp3⁻ (0.2 × 10⁶) T cells from B6 Foxp3^EGFP animals. Mice were euthanized on day 7 posttransplantation, and donor-derived CD4⁺ Foxp3⁺, CD8⁺ Foxp3⁺, CD4⁺ Foxp3⁻, and CD8⁺ Foxp3⁻ T cells were sorted from the spleens and livers of recipients. (A) Unsupervised hierarchical clustering on differentially expressed genes from CD4⁺ and CD8⁺ Tregs and Tcons. Each column represents an individual sample, and each row represents a single gene. Expression values are scaled by rows with values greater than the mean shown in red and values less than the mean shown in blue, with intensity of color corresponding to relative level of expression. Data are from 3 replicates that were each derived from pooled samples from 7 mice. (B) Principal component analysis of CD4⁺ and CD8⁺ Treg and Tcon populations showing that populations primarily differ across principal component 2, with CD8⁺ Tregs more closely related to CD4⁺ Tregs than CD4⁺ and CD8⁺ Tcon populations. (C-D) Expression level of a canonical Treg-associated (Pacholczyk et al³¹  and Feuerer et al³⁹ ) and a Tcon (inverse Treg) gene signature across CD8⁺ Treg, CD8⁺ Tcon, CD4⁺ Treg, and CD4⁺ Tcon samples. (E-F) Venn diagram showing the number of genes significantly overexpressed (E) or underexpressed (F) in CD8⁺ T-cell populations relative to CD4⁺ T-cell populations. **P < .01; ***P < .001; ****P < .0001. PC2, Principal Component 2.