Active homeostatic regulation of DC numbers. (A) Schematic representation of the mixed bone marrow (BM) chimeras used in this study. (B) Numbers of CD11c^hi MHC-II⁺ cDC (gated as shown in Figure 2C top) per spleen in mixed BM chimera mice after continuous DT application. Results are expressed as mean value ± SEM; **P < .01; #not statistically significant, analysis of variance (ANOVA). (C) Phenotypic analysis of expanded cDCs in spleen after 11 days of DT application (DT day 11) compared with DCs from untreated mice (No DT). Shown are FACS dot plots showing the percentage of cDCs (C top), cDC subpopulations (C middle), and CD11b expression on DCs (C bottom) from 1 representative mouse spleen. Cells were gated as indicated on top of FACS plots, and numbers indicate percentages in gates shown. (D) Representative histogram overlays of I-A^b, CD40, CD80, CD86 expression by splenic CD11c^hi MHC-II⁺ cDCs after no DT treatment (full line) or 11 days of DT administration (open line). (E) Specific increase of DTR⁻ eGFP⁺ cells in the DC compartment after prolonged depletion of DTR⁺ DCs. Shown are FACS dot plots from 1 representative mouse spleen. For each cell population, an equal number of total cellular events are shown for groups “no DT” and “11” days of DC depletion. Numbers in the dot plot indicate the percentage within the cDC (CD11c^hi MHC-II⁺), B-cell (CD19⁺) and T-cell (CD3⁺) populations. All experiments were repeated 3 times with similar results using 4 to 5 mice per group.