title: The role of suppressor T cells in BCNU-mediated rejection of a syngeneic tumor.
abstract: The present investigation was initiated to determine the mechanism by which 1,3-bis(2-chloro-ethyl)-1-nitrosourea (BCNU) treatment of tumor-bearing mice results in a high percentage of surviving mice which are resistant to subsequent homologous tumor challenge. Spleen cells from C57BL/6 mice bearing the syngeneic LSA ascites tumor failed to demonstrate significant tumor-specific cytotoxic T lymphocyte (CTL) activity when stimulated in vitro with irradiated tumor cells. This lack of CTL activity correlated with the presence and high activity of two types of CTL-regulatory suppressor T cells (Ts), tumor-specific Thy-1+, Lyt-1-2+ and tumor-nonspecific Thy-1+, Lyt-1+2+ cells, as demonstrated by a double-positive selection technique. In contrast, spleen cells from BCNU-treated tumor-bearing mice generated high tumor-specific CTL activity when stimulated in vitro with irradiated tumor cells. This CTL activity correlated with the lack of demonstrable tumor-specific Ts and greatly diminished tumor-nonspecific Ts activity. The tumor-specific helper activity of Thy-1+, Lyt-1+,2- cells was found to be similar in both BCNU-treated and untreated tumor-bearing mice. BCNU-treated mice that survived a primary LSA tumor challenge (referred to as BCNU-cured mice) resisted subsequent challenge with the homologous (LSA) but not with a heterologous syngeneic tumor (EL-4). However, rejection of a secondary challenge with LSA tumor by BCNU-cured mice was inhibited by adoptive transfer of spleen cells from either normal mice or mice bearing LSA tumors. Furthermore, LSA tumor cells that failed to evoke tumor-specific CTL activity in normal mice could induce high CTL activity in BCNU-cured mice. The present study suggests that, in addition to its direct tumoricidal activity, BCNU inhibits the induction of tumor-specific Ts, thereby explaining why a high percentage of mice survive a primary syngeneic tumor challenge after treatment with BCNU, and also resist subsequent rechallenge with the homologous tumor.
authors.forename: M
authors.initials: M
authors.lastname: Nagarkatti
authors.forename: A M
authors.initials: AM
authors.lastname: Kaplan
mesh_terms: D000818:Animals; D002330:Carmustine / Q000494:pharmacology*; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D005260:Female; D006084:Graft Rejection / Q000187:drug effects*; D007113:Immunity, Innate / Q000187:drug effects; D007116:Immunization, Passive; D007942:Leukemia, Experimental / Q000188:drug therapy / Q000235:genetics / Q000276:immunology*; D008213:Lymphocyte Activation / Q000187:drug effects; D008223:Lymphoma / Q000188:drug therapy / Q000235:genetics / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009368:Neoplasm Transplantation; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000187:drug effects / Q000276:immunology* / Q000637:transplantation; D013953:Thymus Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000276:immunology
chemical_list: D002330:Carmustine