Increased nitric oxide production by airway cells of sensitized and challenged IL-10 knockout mice.

The anti-inflammatory cytokine interleukin (IL)-10 suppresses inducible nitric oxide synthase (iNOS); therefore, NO production should increase in the absence of IL-10. Production of NO (as nitrite) by bronchoalveolar lavage cells of IL-10 knockout ((-/-)) mice was assessed after ovalbumin sensitization and airway challenge (S/C) and was compared with the IL-10-sufficient, wild-type (WT) C57Bl6. Eosinophil recruitment occurred in S/C WT and IL-10(-/-) mice, suggesting allergic airway inflammation. Alveolar macrophages (per g mouse) were unchanged (approximately 3x10(4) cells) with the exception of a doubling in the S/C IL-10(-/-) mice (approximately 6x10(4) cells, P<0.05). NO production (per million cells) was doubled in cells from S/C IL-10(-/-) (15.3 microM) mice compared with WT (7.6 microM, P<0.05). Inhibition of iNOS by L-N(5)-(1-iminoethyl)-ornithine reduced NO production in all S/C mice, confirming that the increase was a result of up-regulation of iNOS. We conclude that IL-10 is a critical cytokine regulating iNOS in murine airway cells and that its absence can lead to up-regulation of iNOS and development of allergic airway inflammation.

Immunogenetic and oncogenic properties of rat trophoblast cell lines.

PROBLEM: The nature of major histocompatibility complex (MHC) antigen expression on rat placentas, trophoblast cell lines, and tumors derived from trophoblast cells was explored. METHOD OF STUDY: Cytohistochemical and flow cytometric analysis and molecular techniques. RESULTS: MHC antigen expression and genomic imprinting on the placenta and on trophoblast cells varies with the time of gestation and with the type of MHC antigen. CONCLUSIONS: There is no correlation in trophoblast cells between class I expression and cell ploidy, on the one hand, and malignant potential, on the other hand. Genomic imprinting of class I antigens in the rat placenta is a quantitative phenomenon.

Malignant potential, major histocompatibility complex antigen expression, and genomic imprinting of rat trophoblast cell lines.

Invasive growth, variation in major histocompatibility complex antigen expression, and genomic imprinting are important properties of both trophoblast cells and malignant tumors. This study, undertaken to address these three issues, used cultured trophoblast cell lines derived from Day 11/12 rat placentas of all mating combinations of the DA and WF inbred strains. In addition, genomic imprinting was also examined in intact rat placentas from Days 11-19. There was no correlation in trophoblast cells between class I antigen expression, DNA content, and cell ploidy on the one hand and oncogenic potential on the other hand. The constitutive suppression of class II antigens in the trophoblast cells could not be abrogated by treatment with interferon-gamma, whereas such treatment always maximally induced class I antigen expression regardless of the initial resting levels. The trophoblast cells at Day 11/12 expressed both maternal and paternal class I antigens, and studies in whole placental tissues showed that the imprinting of the maternal class I antigens was manifested by a decreased level of expression rather than an absence of expression. Thus, genomic imprinting in the rat placenta is a quantitative, rather than an all-or-none, phenomenon.

Role of methylation in placental major histocompatibility complex antigen expression and fetal loss.

The purpose of this study was to determine the role of gene methylation on major histocompatibility complex (MHC) antigen expression in the rat placenta, specifically: 1) the constitutive suppression of labyrinthine class I genes and of all class II genes, 2) genomic imprinting of class I genes, and 3) the amount of fetal loss in relationship to gene methylation. Placentas from all four mating combinations, or a subset thereof, of the inbred DA and WF strains of rats were studied simultaneously through 1) molecular assessment of their levels of methylation at various stages of pregnancy and changes in methylation after treatment with 5-azacytidine and 2) immunohistochemical determination of their MHC class I and class II antigen expression. Treatment with 5-azacytidine caused demethylation of both class I and class II genes, the level depending upon the method of administration of the drug. Treatment with 5-azacytidine did not, however, alter the expression of either the class I or class II antigens. Hence, demethylation is not involved in the constitutive suppression of labyrinthine class I genes or that of all placental class II genes, and it is not involved in the genomic imprinting of placental class I genes. The effect of 5-azacytidine on fetal loss is due to its direct cellular effects and not to an immunological mechanism.

The relative roles of MHC and non-MHC antigens in bone marrow transplantation in rats. Graft acceptance and antigenic expression on donor red blood cells.

In order to investigate the influence of MHC and non-MHC genes in bone marrow transplantation, various combinations of congenic and inbred strains of rats were used as donors and recipients. A standard regimen of busulfan and cyclophosphamide treatment was used to condition the recipients. The resultant survival patterns of the animals indicated that: (1) a difference across the entire RT1 (MHC) complex is sufficient for the induction of fatal graft-versus-host disease (GVHD) in 100% of the engrafted animals; and (2) the blood group antigens RT2 and RT3, which are controlled by non-MHC genes, do not cause bone marrow graft rejection or GVHD. There were sequential changes of expression in surface alloantigens on the red cells in different donor-recipient combinations without other hematologic changes in the busulfan-cyclophosphamide conditioned bone marrow chimeras.