Abstract. Endoglin is a homodimeric membrane glycoprotein which can bind the 131 and 133 isoforms of transforming growth factor-13 (TGF-13). We reported previously that endoglin is upregulated during monocyte differentiation. We have now observed that TGF-13 itself can stimulate the expression of endoglin in cultured human monocytes and in the U-937 monocytic line. To study the functional role of endoglin, stable transfectants of U-937 cells were generated which overexpress L-or S-endoglin isoforms, differing in their cytoplasmic domain. Inhibition of cellular proliferation and downregulation of c-myc mRNA which are normally induced by TGF-t31 in U-937 cells were totally abrogated in L-endoglin transfectants and much reduced in the S-endoglin transfectants. Inhibition of proliferation by TGF-132 was not altered in the transfectants, in agreement with the isoform specificity of endoglin. Additional responses of U-937 cells to TGF-131, including stimulation of fibronectin synthesis, cellular adhesion, platelet/endothelial cell adhesion molecule i (PECAM-1) phosphorylation, and homotypic aggregation were also inhibited in the endoglin transfectants. However, modulation of integrin and PECAM-1 levels and stimulation of mRNA levels for TGF-131 and its receptors R-I, R-II, and betaglycan occurred normally in the endoglin transfectants. No changes in total ligand binding were observed in L-endoglin transfectants relative to mock, while a 1.5-fold increase was seen in S-endoglin transfectants. The degradation rate of the ligand was the same in all transfectants. Elucidating the mechanism by which endoglin modulates several cellular responses to TGF-131 without interfering with ligand binding or degradation should increase our understanding of the complex pathways which mediate the effects of this factor.

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Acute parvovirus B19 infection is a risk for pregnant women. After vertical transmission the infected fetus may develop hydrops fetalis. Since B19 infection occurs mainly during childhood, children represent a main source for virus transmission. In order to determine whether certain groups in the German population show increased risks for B19 infection we analysed the seroprevalence using 6583 sera collected from adults in former Eastern and Western Germany during the German National Health Survey and 649 sera from healthy Thuringian children and adolescents. In adults the overall seroprevalence was 72.1%, rising from 20.4% in children (1-3 years) and 66.9% in adolescents (18-19 years) to 79.1% in the elderly (65-69 years). Significant differences were observed between females (73.3%) and males (70.9%) and between inhabitants of small (74.8%) and big cities (69.0%) but not between people of the former Eastern (72.8%) and Western states (72.0%) of Germany. For women during childbearing age (18-49 years) highest values were observed in those living together with two or more children (81.6%) and in women with occupational contact with children aged <6 years (88.9%). In contrast seroprevalence was significantly lower in age-matched female singles (64.8%) and in women with occupational contact with children aged >6 years and adolescents (63.8%).

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