published_or_final_version / Medicine / Master / Doctor of Medicine

No description available.

Prostaglandin E2, postulated to be immunosuppressive to the tumor bearing host, is produced and excreted in elevated quantities by many tumors. Arachidonic acid, the precursor molecule for PGE2, is released from membrane phospholipids by phospholipase A2. Phospholipase A2 has been proposed as the rate limiting enzyme in the production of prostaglandin E2.Phospholipase A2 from different sources varies in substrate specificities, pH optima, and Ca ++ concentration requirements. Therefore, the determination of its specific activity depends on the development of appropriate incubation, extraction, and identification methodologies.This study attempted to develop methodologies for determination of PLA2 activity using enzymes from snake venom, mouse liver, and normal and tumored mouse mammarytissue. The method of substrate preparation, kind of substrate, amount of protein, length of incubation, and addition of KC1 and deoxycholate were varied. Reaction products were extracted and isolated with hexame, and methylated with diazomethane. The methyl esters were identified by gas liquid chromatography. Quantitative analyses were based on proportionality of experimental peak areas to internal standard peak area.Activity could not be demonstrated with snake venom or liver PLA2 preparations. Low specific activity was obtained in some tumor and normal mammary tissue extracts. These studies will be used as a basis for developing an optimal assay system for PLA2 from normal and tumored mouse mammary tissue.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1994. / Includes bibliographical references (leaves 111-122). / Microfiche. / x, 122 leaves, bound ill. 29 cm

published_or_final_version / Pathology / Doctoral / Doctor of Philosophy

Ball State University LibrariesLibrary services and resources for knowledge buildingMasters ThesesThere is no abstract available for this thesis.

C57B1/6 mice bearing Lewis lung carcinoma CLLC) are suppressed in their ability to generate cytotoxic T lymphocytes against the LLC tumor associated antigens. Since LLC have previously been shown to secrete the immunosuppressive factor PGE2, indomethacin, a prostaglandine synthetase inhibitor, was administered to LLC-bearing mice in their drinking water to prevent the immunosuppression typical of tumor bearers. The indomethacin treated tumor-bearers displayed an increase in their cytotoxic responses to the LLC tumor associated antigens. Thus the immunosuppression found in mice bearing LLC could be due to prostaglandin synthesis. Production of PGE2 by tumor cells may be a mechanism by which the tumors escape immune mediated destruction.Ball State UniversityMuncie, IN 47306

Natural killer (NK) cells are important in limiting tumor dissemination. The NK activity in C57B1/6 mice bearing Lewis lung carcinoma (LLC) was monitored during tumor development. During the initial period of tumor growth, NK activity was enhanced. As tumor growth progressed, NK activity became suppressed. Depletion of macrophages from the spleen cells of tumor-bearing mice restored the NK cytotoxic response. Plasma prostaglandin E2 (PGE2) concentrations were measured by a radioimmunoassay and found to become elevated during the course of tumor growth. To determine whether the suppressed NK activity might have been a result of the elevated levels of PGE2, mice were treated with a prostaglandin synthesis inhibitor, indomethacin. Indomethacin treatment prevented the rise in plasma PGE2 concentrations and the suppression in NK activity. These results support the hypothesis that the suppression of NK activity in tumor bearers is mediated by PGE2 which might be produced by the host's suppressor macro-phages.

During tumor growth there are a series of phenotypic and functional changes that occur in macrophages (M_Φ) that ultimately lead to the immunosuppression of the tumor-bearing host (TBH). To investigate the phenotypic changes of M_Φ during tumor growth, we examined the expression of the M_Φ surface antigens, Mac-1, Mac-2, Mac-3, and Ia on peritoneal and splenic M_Φ. In the peritoneal cavity there was no change in the percentage of Mac-1⁺ M_Φ but a decrease in the percentage of Mac-2⁺, -3⁺, and Ia⁺ M_Φ during tumor growth. In addition, three distinctly sized populations of peritoneal M_Φ, showing differential antigen expression, also shifted during tumor growth. In the peritoneal cavity there was a decrease in the percentage of M_Φ co-expressing the Mac-2, -3, and Ia antigens, leading to a shift towards Mac-1⁺ 2⁻ 3⁻ Ia⁻ TBH M_Φ. In splenic M_Φ, the percentage of Mac-1⁺, -2⁺, and -3⁺ M_Φ increased, while the percentage of Ia⁺ M_Φ decreased. Splenic M_Φ showed an increase in the percentage of M_Φ co-expressing Mac-1, -2, and -3 antigens and a decrease in the percentage of M_Φ co-expressing Ia, leading to a shift towards a Mac-1⁺ 2⁺ 3⁺ Ia⁻ TBH M_Φ. Taken together, these data suggest that tumor growth alters the phenotype of M_Φ and causes a shift in M_Φ subpopulations. After measuring the phenotypic changes in M_Φ during tumor growth, changes in M_Φ accessory function to T cells were assessed. TBH M_Φ have significantly reduced accessory activity for autoreactive T cells. This reduction is caused by decreased Ia antigen expression and increased production of the suppressor molecule, prostaglandin (PG). TBH M_Φ down-regulated autoreactive T cell responsiveness to interleukin (IL)-1, IL-2, and IL-4. In addition to TBH M_Φ reducing T cell responsiveness to cytokines, TBH CD4⁺ T cells alone were less responsive to the cytokines IL-1, IL-2, and IL-4. To examine the responsiveness of M_Φ to activation signals, lipopolysaccharide (LPS) was incubated with normal and TBH splenic M_Φ and assessed for their phenotypic, functional, and cell-cycle changes. The data showed that TBH M_Φ had a decreased responsiveness to LPS. We showed that there was a shift from an Ia⁺ M_Φ in the normal host to an Ia⁻ M_Φ in the TBH. Concomitant with the shift in TBH M_Φ Ia⁻ phenotype was a change in TBH M_Φ function. Normal and TBH Ia⁻ M_Φ were suppressor M_Φ. TBH Ia⁻ M_Φ, however, suppressed autoreactive and alloreactive CD4⁺ T cells significantly more than could their normal counterparts. Tumor growth causes quantitative and qualitative changes in Ia⁻ suppressor M_Φ. Although Ia⁻ M_Φ-mediated suppression seemed to be the major source of down-regulation of CD4⁺ T cells, CD8⁺ T cells were not without fault. In the TBH, there was an increase in the percentage of CD8⁺ T cells and an increase in CD8⁺ T cell-mediated suppression. In conclusion, tumor growth leads to a change in immunoregulation that causes suppression of the immune response. / Ph. D.

Previous reports indicate that anti-tumor activity arising from systemically injected P. acnes is macrophage-mediated, whereas anti-tumor activity arising from locally injected P. acnes is T cell-mediated. It is possible these P. acnes-induced cytotoxic T cells arise via the Interleukin cascade. Therefore, this study investigated the involvement of Interleukin 2 (IL 2) and Interleukin 3 (IL 3), known components of the Interleukin cascade, in local P. acnes-mediated anti-tumor action. A 500 ug dose of heat-killed stationary phase P. acnes given simultaneously with 10⁴ tumor cells was found to inhibit tumor formation completely, therefore this amount was used as a standard dose throughout the study. Unvaccinated counterparts developed palpable tumors two weeks after tumor cell administration. Lower doses of vaccine protected animals from tumor growth to a lesser degree. A vaccine prepared from logarithmic phase P. acnes exerted a moderate anti-tumor effect in some cases. IL 2 and IL 3 levels were measured in vitro in normal BALB/c mice (N), tumor-bearing mice (TBH), normal vaccinated mice (N+V), and mice receiving both tumor cell and vaccine injection (T+V). IL 2 and IL 3 production was maintained in both N and N+V host splenocyte cultures throughout the study. In a similar fashion, levels of IL 2 and IL 3 in T+V host splenocyte cultures were comparable to those of N+V hosts. However, TBH splenocyte production of IL 2 and IL 3 began to decline when tumors became palpable, at Day 14 after tumor cell inoculation. By Day 28, TBH IL 2 and IL 3 levels were <15% of normal control levels. Causes for this suppression of IL 2 and IL 3 production in TBH were examined. From reports of others it appeared that suppression may be mediated through prostaglandin(s). Addition of the prostaglandin inhibitor indomethacin to splenocyte cultures greatly enhanced IL 2 production by N, N+V and T+V splenocytes, but failed to restore IL 2 production in TBH splenocyte cultures to normal levels. Thus, it appeared prostaglandins were not directly responsible for the majority of suppression seen in TBH. In the non-tumor-burdened host, prostaglandin appeared to play a homeostatic role regarding IL 2 production. Indomethacin-treatment had little effect on IL 3 production. Nylon wool fractionation of N, TBH, N+V and T+V splenocytes suggested a cell removed by nylon wool treatment was largely responsible for the suppression of IL 2 and IL 3 production in TBH. No obvious presence of functional suppressor cells was noted in N, N+V or T+V splenocytes. From these results, it appeared that P. acnes administration maintains and/or restores IL 2 and IL 3 production, thus favoring the production of CTL. In addition, the suppression of IL 2 and IL 3 production seen in TBH may be due to a nylon wool adherent suppressor cell. A model describing the effect of P. acnes administration on local anti-tumor activity was presented. / Master of Science