Biomedical subjects

F Leutmezer

Publications and source records attributed to F Leutmezer.

21 records · Page 2Linked to original sources

PubMed1997

Effects of 1 alpha,25-dihydroxyvitamin D3 and cytokines on the expression of MHC antigens, complement receptors and other antigens on human blood monocytes and U937 cells: role in cell differentiation, activation and phagocytosis.

The effect of calcitriol/1 alpha,25-dihydroxyvitamin D3, alone and in combination with cytokines, on the expression of various antigens (Ag) on human peripheral blood monocytes and U937 cells was studied by flow cytometry. Both constitutive and interferon-gamma (IFN-gamma), interleukin-4 (IL-4), IL-6 and tumour necrosis factor-alpha (TNF-alpha)-induced human leucocyte antigen (HLA)-DR, HLA-DP and HLA-DQ Ag expression on monocytes was significantly down-regulated by calcitriol, IL-10 and transforming growth factor-beta (TGF-beta). The effects of calcitriol were concentration dependent and reached maximal inhibitory levels after 3-5 days. Modulation of HLA-DR by calcitriol and IFN-gamma at the protein level correlated with the amount of mRNA specific for the HLA-DR alpha-chain, as judged by Northern blot analysis. The basal as well as IL-4, IL-6, IFN-gamma, TNF-alpha and TGF-beta-driven levels of HLA-ABC Ag were significantly diminished by calcitriol. On U937 cells calcitriol markedly induced CD11a and CD11b expression and weakly up-regulated CD11c whereas on monocytes, constitutive CD11a, CD11b and CD11c expression was significantly down-regulated by calcitriol. The expression of CD14 Ag was strongly induced on U937 cells but only modestly on monocytes. Both the basal level of CD71 and IL-4, IFN-gamma or TNF-alpha-driven expression was diminished on calcitriol-treated U937 cells. In addition, calcitriol suppressed the expression of CD71 Ag on monocytes. The ability of monocytes to phagocytize opsonized Escherichia coli was diminished by calcitriol. Our results demonstrate that calcitriol, alone or in combination with cytokines, modulates expression of MHC, CD11b, CD11c, CD14 and CD71 Ag on both monocytes and U937 cells, and impairs the phagocytic property of monocytes.

Antigens, CD↗

PubMed1997

Low glutamine concentrations induce phenotypical and functional differentiation of U937 myelomonocytic cells.

L-Glutamine is the most abundant free amino acid of the human body and is essential for the culture of many cell types. Clinically, reduction of glutamine by administration of glutaminase or the use of glutamine analogs is a common therapy for patients with acute lymphocytic leukemia. In the current study, we investigated the influence of glutamine concentrations on the human myelomonocytic cell line U937. Decreasing the glutamine concentration evoked a reduction in DNA synthesis (R2 = 0.9885, P < 0.0001), increased cell volume (P < 0.01) and the cytoplasm/nuclear ratio, and enhanced the development of vacuoles but did not influence cell viability. Culturing cells in reduced concentrations of glutamine augmented the percentage of cells expressing CD64 (Fc receptor for IgG/FcgammaRI, P < 0.01), CD11b (complement receptor type 3/CR3, P < 0.001) and CD71 (transferrin receptor, P < 0.05). The percentage of U937 cells expressing CD23 (low affinity receptor for IgE/FcepsilonRII) was increased at low concentrations of glutamine at both the protein (P < 0.01) and mRNA levels. The percentage of U937 cells phagocytizing opsonized E. coli (P < 0.001) or latex particles (P < 0.001) was enhanced by lowering the glutamine concentration. In conclusion, reducing glutamine concentration causes differentiation of the cell line U937 along the monocytic pathway. These effects may indicate a mechanistic basis for prior published evidence that glutaminase and glutamine antagonists are effective anti-tumor agents.

Antibodies, Monoclonal↗

PubMed1995

Modulation of IgA, IgE, and IgG Fc receptor expression on human mononuclear phagocytes by 1 alpha,25-dihydroxyvitamin D3 and cytokines.

The effects of 1 alpha,25-dihydroxyvitamin D3/calcitriol on the expression of Fc receptors (FcR) for IgA (Fc alpha R), IgE (Fc epsilon RII), and IgG (Fc gamma R) on human peripheral blood monocytes and the cell lines U937, THP-1, and Mono Mac-6, in combination with various cytokines, was examined by flow cytometry. On both monocyte-derived macrophages and the myelomonocytic cell lines, Fc alpha R/CD89 expression was induced by calcitriol alone and additively in combination with tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), and granulocyte-macrophage colony-stimulating factor. Constitutive and interleukin-4 (IL-4)-driven Fc epsilon RII/CD23 expression was markedly diminished on calcitriol-treated U937 cells and monocytes. Fc epsilon RII was also triggered by IFN-gamma, TNF-alpha, and IL-6 on all the cell lines, an effect blocked by calcitriol. On monocytes, the basal level and IFN-gamma-induced Fc gamma RI/CD64 expression was down-regulated by calcitriol and IL-4. The expression of Fc gamma RII/CD32 on monocytes was strongly suppressed by calcitriol. Transforming growth factor-beta induced Fc gamma RIII/CD16 on monocytes, an effect opposed by calcitriol. The ability of calcitriol-treated monocytes to phagocytose IgG-sensitized ox erythrocytes was diminished. Our results demonstrate that calcitriol, alone or in combination with cytokines, modulates Fc alpha R, Fc epsilon RII, Fc gamma RI, and Fc gamma RII expression on human mononuclear phagocytes, as well as Fc gamma R-mediated phagocytosis.

Calcitriol↗