Alleva, David G.2014-03-142014-03-141994-09-01etd-12142006-131852http://hdl.handle.net/10919/40420Macrophages (Mφ) are a major immune cell involved in anti-tumor responses. Mφ activities such as tumor cytotoxicity. presentation of tumor-associated antigens, and stimulation of anti-tumor lymphocytes are all involved in the battle against tumor growth. However, other Mφ activities such as cell growth promotion, angiogenesis, and suppression of anti-tumor lymphocytes aid in tumor growth. This dissertation discusses how tumors control Mφ activities to create favorable environments for tumor growth. Assessment of tumor- and Mφ-derived molecules has enabled me to design models of communication between tumors, Mφ, and other immune cells. A major research focus was to determine how tumor-derived molecules induce Mφ suppressor activity and control Mφ cytotoxicity. Tumor growth induced Mφ to suppress T lymphocyte proliferation by increasing Mφ production of the suppressor molecules prostaglandin E₂ (PGE₂), nitric oxide (NO), and tumor necrosis factor-α (TNF-α). A major finding was that TNF-α's normal up-regulatory action on T-cell proliferation switched to a suppressor action when Mφ were present. The autocrine action of increased TNF-α levels during tumor growth stimulated Mφ PGE₂ and NO synthesis, which suppressed T-cell proliferation.xxiv, 404 leavesBTDapplication/pdfenIn CopyrightLD5655.V856 1994.A545MacrophagesTumors -- GrowthDissertationhttp://scholar.lib.vt.edu/theses/available/etd-12142006-131852/