Source and inhibition of uPA-mediated MDSC recruitment. Normal BALB/c mice were injected intraperitoneally 8 times every other day with either saline as control, or 1 μg recombinant uPA. Two hours after the last injection, the BM, spleen, blood, and IP cells were harvested and stained for (A) dendritic cells (CD11c) and (B) macrophages (F4/80), and analyzed by flow cytometry. (C) Normal BALB/c mice were injected intraperitoneally 2 times every other day with either saline as control, or 1 μg recombinant uPA. Two days after the last injection, the BM, spleen, blood, and IP cells were harvested and stained for MDSC analysis by flow cytometry. (D) FVB and FVB MMP-9^−/− mice were injected intraperitoneally with 1 μg recombinant uPA, or saline as control, 2 times every other day. The IP cells were harvested 2 hours after the last injection and stained for MDSC analysis by flow cytometry. (E) Normal BALB/c mice were injected intraperitoneally with 1 μg recombinant uPA alone, or in conjunction with 12 μg recombinant PAI-1. Two hours later, IP cells were harvested and stained for MDSC analysis by flow cytometry. Error bars representing SEM and P values are provided.