Flt3L expands pDCs and cDCs in the spleen and bone marrow. Rapamycin blocks cDC expansion (but not pDC expansion). Total numbers of pDC (CD11c⁺PDCA-1⁺) (A) and cDC (CD11c^hi) (B) DC subsets in DO11.10-tg Rag-2^−/− BALB/c mice per 10⁶ splenocytes. Mice (n = 6-10) were treated 3 times per week for 3 weeks IP with Flt3L, Flt3L/OVA_323-339, Flt3L/OVA_323-339/ rapamycin, or Flt3L/irrelevant peptide (FIX peptide). Enumeration of pDCs (C) and cDCs (D) as a percentage of total DCs (CD11c⁺). (E) Representative dot plot of naïve DO11.10-tg Rag-2^−/− BALB/c mice splenocytes showing gating scheme for pDCs and cDCs. Total numbers of pDC (CD11c⁺PDCA-1⁺) (F) and cDC (CD11c^hi) (G) DC subsets in DO11.10-tg Rag-2^−/− BALB/c mice per 10⁶ bone marrow cells. Mice (n = 6-10) were treated 3 times per week for 3 weeks IP with Flt3L, Flt3L/ OVA_323-39, Flt3L/OVA_323-339/ rapamycin, or Flt3L with an irrelevant peptide (FIX peptide). Enumeration of pDCs (H) and cDCs (I) as a percentage of total DCs (CD11c⁺). (J) Representative dot plot of naïve DO11.10-tg Rag-2^−/− BALB/c mice bone marrow cells showing gating scheme for pDCs and cDCs. Plots are representative of data from 6 animals per experimental group. Statistical differences were determined by 2-way ANOVA with Bonferonni’s posttest comparisons.