Leukocyte extravasation: an immunoregulatory role for alpha-L-fucosidase?

Fucosylated oligosaccharides and glycoconjugates have been implicated in several biological events, including the cell-cell adhesion processes that mediate inflammation. Alpha-L-fucosidase (ALF) is an exoglycosidase that is involved in the hydrolytic degradation of alpha-L-fucose from glycoconjugates. In this study, we investigated the potential role of ALF in regulation of leukocyte migration. Measurement of transendothelial migration in response to CCL5 demonstrated that pretreatment of monocytic cells with ALF reduced migration (p = 0.0004) to a greater extent than treatment of the endothelial monolayer (p = 0.0374). Treatment with ALF significantly reduced the adhesion of monocytic cells to immobilized P-selectin.Fc. A murine model of experimental autoimmune uveitis was then used to show that treatment of splenic cells with ALF produced an 8.6-fold decrease in rolling and a 3.2-fold decrease in cell migration across the retinal vasculature. Further in vitro studies demonstrated that treatment of monocytes with the chemokines CCL3 or CCL5 increased the level of mRNA encoding ALF; this was accompanied by the detection of significant increases in both the 51- and 56-kDa components of ALF by Western blotting. Treatment of monocytic cells with ALF for 2 h significantly reduced the cell surface expression of CD31, with a further decrease in expression observed after 5 h (p = 0.002). Thus, CD31 and fucosylated ligands of P-selectin seem to be the candidates through which ALF mediates its effect in vitro. These data identify a previously unrecognized immunoregulatory role for ALF in late stages of inflammation.

Interferon-gamma inhibits extravillous trophoblast cell invasion by a mechanism that involves both changes in apoptosis and protease levels.

BACKGROUND: Extravillous trophoblast cell (EVT) invasion of decidua and inner third of the myometrium is critical for a successful pregnancy. Many decidual factors are likely to play a role in regulating this process, including uterine natural killer (uNK) cell-derived cytokines. HYPOTHESES: 1) uNK cells are a major source of IFN gamma (IFN-gamma) and 2) IFN-gamma inhibits EVT invasion via an increase in EVT apoptosis and/or a decrease in active protease levels. METHODS: Total decidual and uNK cells from 8-10 wk and 12-14 wk gestational age were cultured. IFN-gamma mRNA (real-time RT-polymerase chain reaction) and protein levels (FastQuant multicytokine analysis) were determined. EVT invasion in the presence of IFN-gamma or anti-IFN-gamma-neutralizing antibodies was assessed. Trophoblast apoptosis and proliferation was assessed in explants by immunohistochemistry for M30 and Ki67. Substrate zymography was performed to determine levels of secreted MMP2, MMP9, and uPA. RESULTS: mRNA and protein for IFN-gamma was detected in both total decidual and uNK cell fractions. Trophoblast invasion was inhibited by IFN-gamma. The level of M30-positive EVT was increased in the presence of IFN-gamma whereas levels of secreted MMP2 were decreased. CONCLUSIONS: uNK cells are a source of IFN-gamma within early human pregnancy decidua. Mechanisms of IFN-gamma inhibition of EVT invasion include both increased EVT apoptosis and reduced levels of active proteases.

Expression of angiogenic growth factors by uterine natural killer cells during early pregnancy.

Remodeling of uterine spiral arteries is critical for the continuation of a successful pregnancy. Uterine natural killer (uNK) cells are the predominant leukocyte population in the early pregnant decidua, and a role for these cells in spiral artery remodeling in pregnancy has been suggested. Angiogenic growth factors were measured in isolated uNK and total (unseparated) decidual cells (8-10 or 12-14 weeks gestation, n=5 each gestational age) after culture for 48 h. Angiopoietin (Ang)1, placental growth factor, transforming growth factor-beta1 (TGF-beta1), and vascular endothelial growth factor (VEGF)-C were measured by enzyme-linked immunosorbent assay. Angiogenin, Ang2, fibroblast growth factor basic, intercellular adhesion molecule (ICAM)-1, keratinocyte growth factor (KGF), platelet-derived growth factor-BB, and VEGF-A were measured using a FASTQuant angiogenic growth factor multiplex protein assay. Levels of Ang2, ICAM-1, and KGF, secreted by the total decidual fraction, decreased with increasing gestational age. uNK levels of Ang2 and VEGF-C also decreased with increasing gestational age. At 8-10 weeks gestation, there was no difference in the level of Ang1, Ang2, TGF-beta1, and VEGF-C secreted by uNK cells and the total decidual fraction. At 12-14 weeks, uNK cells secreted significantly lower levels of VEGF-C than the total decidual fraction. Early pregnancy decidua is a major source of angiogenic growth factors whose levels decrease with increasing gestational age, suggesting that they may play a role in spiral artery remodeling. uNK cells appear to be a prominent source of Ang1, Ang2, TGF-beta1, and VEGF-C within the placental bed.