Characterization of BM-transplanted chimeric mice. (A) Flow cytometric analysis of donor myeloid progenitor cells in the BM of bitransgenic (Tg) or wild-type (WT) BM-transplanted recipient mice. Tg→WT: BM transplantation from c-fms-rtTA/(TetO)₇-CMV-MMP12 bitransgenic mice (CD45.1⁺) to wild-type (CD45.2⁺) chimeric mice; WT→Tg: BM transplantation from wild-type mice (CD45.2⁺) to bitransgenic (CD45.1⁺) chimeric mice; +DOX, doxycycline treated; −DOX, doxycycline untreated; n = 7-10, *P < .05. (B) Flow cytometric analysis of donor CD11b⁺GR-1⁺ cells from the BM and spleen of bitransgenic and wild-type transplanted chimeric mice, n = 7-10; *P < .05. (C) CFSE-labeled wild-type CD4⁺ T cells were stimulated with anti-CD3 mAb plus anti-CD28 mAb for 3 days in the presence or absence of donor CD45.1⁺ or CD45.2⁺ CD11b⁺Gr-1⁺ cells isolated from BM-transplanted chimeric mice. The ratio between CD11b⁺Gr-1⁺ cells:CD4⁺ T cells was 1:5. Proliferation of labeled CD4⁺ T cells was analyzed by flow cytometry. Peaks represent cell division cycles. (D) The concentration of IL-2 in the above cultured medium was measured by ELISA, n = 7-10; **P < .01. (E) The concentrations of IL-6 and IL-10 were measured from the plasma of bitransgenic and wild-type transplanted chimeric mice, n = 7-10; *P < .05, **P < .01.