Residence time of MDSC subpopulations in tumor-bearing mice. (A) Parabiotic mice were established between C57BL/6 (CD45.2) and congenic B6. SJL (CD45.1) mice, and 3LL tumors were subcutaneously inoculated to each parabiont 40 days after surgery. Seven days after tumor inoculation, parabionts were surgically separated, and then the chimerism of neutrophils and monocytes was analyzed at various times after separation. (B) Representative CD45.1 profiles in macrophages and neutrophils in the tumor and spleen after separation. (C) Chimerism of neutrophils (circles) and monocytes/ Mφs (square) in tumor (red), spleen (green), blood (blue), and bone marrow (black) at various time points after surgical separation. Each time point represents the mean (± SD) of 3 mice.