Expansion of myeloid immunosuppressive cells in the PB and spleen of BALB-neuT mice. (A) Correlation between age and increased percentages of Gr-1/Mac-1 double-positive cells in the PB of BALB-neuT females. Results are from 47 independent evaluations. (B-C) Correlation between tumor multiplicity and percentage of Gr-1/Mac-1/ER-MP12 triple-positive cells in the PB (B) and spleen (C) of tumor-bearing BALB-neuT females (□) and sibling BALB/c females (controls, ▪). Error bars indicate SD. (D-E) Proliferative response of splenocytes from individual BALB-neuT females with distinct tumor multiplicities to immobilized anti-CD3 (10 μg/mL) plus IL-2 (50 U/mL) (D) and allogeneic C57/Bl6 irradiated spleen cells (E). Results are expressed as percentage of control BALB/c proliferation on day 3 in panel D and day 5 in panel E. (F) Increased proliferative alloresponse of splenocytes from individual BALB-neuT females (□) upon removal of Gr-1/Mac-1 cells (▪), expressed as counts per minute ([cpm]; mean of 6 replicates ± SD).