Suv39h DKO results in thymic involution, selective loss of CD8⁺ T cells, myeloid skewing, and increased frequency of memory cells. (A) Frequencies of CD4⁺, CD8⁺, double negative (DN), and DP thymocytes from the thymus of Suv39h1 and h2 DKO and control bone marrow chimeras. (B) Representative images of the dissected thymus from WT, Suv39h1-deficient (h1KO), Suv39h2-deficient (h2KO), and DKO donor bone marrow chimeras. (C) Total thymocyte numbers obtained from mechanical homogenization and red-cell lysis of thymus tissue from donor cells of different genotypes. (D) Representative flow cytometry plots of T cells (PI⁻CD45.2⁺TCRβ⁺) from peripheral lymph nodes of DKO and control bone marrow chimeras. (E) Splenic frequencies of CD8⁺, CD4⁺ T cells, and B cells (CD19⁺) from bone marrow chimeras of different genotype donor cells. (F) Splenic frequencies of myeloid cells from bone marrow chimeras of different genotype donor cells. Total myeloid cells (CD11b⁺CD11c⁻), neutrophils (CD11b⁺Ly6g⁺Ly6c^mid), eosinophils (CD11b⁺SiglecF⁺SSC^hi), inflammatory monocytes/macrophages (CD11b⁺Ly6g⁻Ly6c^Hi), and resident monocytes/macrophages (CD11b⁺Ly6g⁻Ly6c^Lo) are shown. Frequencies of naive (CD62L⁺CD44⁻), central memory (CD62L⁺CD44⁺), and effector memory (CD62L⁻CD44⁺) CD8⁺ T cells from the (G) peripheral lymph nodes and (H) spleens of different donor genotypes. Data in panels C, E, F, and H are depicted as individual data points together with mean and SEM and were statistically analyzed by 1-way ANOVA with Sidak multiple comparisons test comparing each genotype with relevant control.