Figure 2. Tumor-Infiltrating DC Are Bone Marrow Derived.

(A–F) Bone marrow chimeric mice were used to assess the origin of CD11c⁺ mDC infiltrating into the tumor. (A,C,E) WT mice are depicted on the left panels; chimeras are as follows: WT mice adoptively transferred with GFP^+/+ bone marrow; or GFP^+/+ mice adoptively transferred with WT bone marrow; GFP^+/+ mice are depicted on the right panels. GL26 cells were implanted in all mice 10 wk after irradiation and treated 17 d later with Ad-Flt3L and Ad-TK. 7 d after the treatment, tumor-infiltrating immune cells and splenocytes were isolated; flow cytometry was performed to detect total GFP⁺ splenocytes (A and B), GFP⁺ tumor-infiltrating microglia (C and D), or GFP⁺ tumor infiltrating mDC (E and F).

Representative dot plots show (A) GFP⁺ (upper boxes, GFP⁺, CD45^hi) or GFP⁻ splenocytes (lower boxes, GFP⁻, CD45^hi); (C) GFP⁺ microglia (upper boxes, GFP⁺, CD45^Int) or GFP⁻ microglia (lower boxes, GFP⁻, CD45^Int); and (E) GFP⁺ mDC (upper boxes, GFP⁺, CD11c⁺) or GFP⁻ mDC (lower boxes, GFP⁻, CD11c⁺) infiltrating into the brain tumors.

The normalized percentage of GFP⁺ splenocytes (B), tumor-infiltrating GFP⁺ microglia (D), and tumor-infiltrating GFP⁺ mDC (F) are shown for each type of chimeric mouse (*, p < 0.05; Mann-Whitney U-test).