Induction and expansion of immunoregulatory macrophages in mice bearing a murine mammary adenocarcinoma

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)


Microbiology and Immunology

First Committee Member

Diana M. Lopez - Committee Chair


Using an immunogenic non-metastatic murine mammary adenocarcinoma (D1-DMBA-3) induced in BALB/c mice by dimethylbenzathracene, it was found that splenocytes from tumor bearers have depressed lymphocyte responses to mitogens and antigens, including tumor associated antigens (TAA). In addition, decreased levels of natural killer and T cell cytotoxic activities were observed in the tumor bearing mice. Macrophages from tumor bearing mice appear to be responsible for the suppression of T and D cell responses to Con A, LPS and TAA observed in tumor bearers. These macrophages also lose the capacity to lyse several tumor cell lines.Increased levels of macrophage progenitors have been observed in blood, bone marrow, lung and liver after tumor implantation. In addition, a significant enhancement of colony stimulating activity (CSA) of the granulocyte-macrophage lineage was detected in the sera from tumor bearing mice. A cell line established in vitro from the D1-DMBA-3 in vivo tumor produces high levels of a factor with CSA. Partial purification of the CSA from the tumor cell line supernatants using CentriCell ultrafiltration and Sephacryl S-300 chromatography revealed that the m.w. of the colony-stimulating factor (CSF) is 30-35,000 kD. CSA from tumor cell supernatants can be neutralized by anti serum to granulocyte-macrophage CSF (GM-CSF) but not with anti macrophage-CSF or anti granulocyte-CSF. Northern and Western blot analyses further confirmed that the tumor constitutively expresses and releases GM-CSF. Macrophages from bone marrow or spleen cells from normal mice cultured with tumor supernatant or rGM-CSF for 3-5 days strongly inhibit normal splenocyte responses to Con A and LPS. In addition, macrophages cultured with tumor supernatants or rGM-CSF reduce their capacity to lyse tumor. Daily i.p. injections for 3 weeks of 10,000 units of rGM-CSF into normal mice induced hemopoietic and immunologic alterations similar to those observed in tumor bearers. Tumor-derived GM-CSF stimulated endothelial cells to exhibit increased leukocyte binding, which may in turn influence leukocyte trafficking into the tumor. These data indicate that GM-CSF plays multiple roles in the regulation of the development, distribution, and function of leukocytes both in peripheral organs and within the tumor which leads to enhancement of tumor growth.


Biology, Cell; Health Sciences, Pathology; Health Sciences, Immunology

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