Decidual NK cells regulate key developmental processes at the human fetal-maternal interface

Human CD56(bright) NK cells accumulate in the maternal decidua during pregnancy and are found in direct contact with fetal trophoblasts. Several mechanisms have been proposed to explain the inability of NK cells to kill the semiallogeneic fetal cells. However, the actual functions of decidual NK (dNK) cells during pregnancy are mostly unknown. Here we show that dNK cells, but not peripheral blood-derived NK subsets, regulate trophoblast invasion both in vitro and in vivo by production of the interleukin-8 and interferon-inducible protein-10 chemokines. Furthermore, dNK cells are potent secretors of an array of angiogenic factors and induce vascular growth in the decidua. Notably, such functions are regulated by specific interactions between dNK-activating and dNK-inhibitory receptors and their ligands, uniquely expressed at the fetal-maternal interface. The overall results support a 'peaceful' model for reproductive immunology, in which elements of innate immunity have been incorporated in a constructive manner to support reproductive tissue development.     

Regenerative Xylem in Inflorescence Stems of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

By inserting entomological needles into the lower parts of young inflorescence stems of three-month-old Arabidopsis thaliana (L.) Heynh var. Colombia plants, we studied the process of regenerative xylem production. Regenerative xylem was formed only in one- to two-day-old inflorescence stems but not in older ones. The regenerative vessels originated from re-differentiation of cortical parenchyma. To characterize the process of regenerative xylem formation, we conducted a histological study from the time of wounding to day 30 after wounding. In the first day after wounding the tissues showed no structural responses except for the wounding itself. After six days, regenerative vessel members were already differentiating in a basipetal pattern, forming a vascular bypass around the wound. Regenerative vessel member formation reached a maximal level on the twelfth day after wounding. Sixteen days after wounding the pith parenchyma started to become loose as if indicating tissue senescence. Altogether, vascular regeneration following wounding in inflorescence stems of Arabidopsis thaliana is similar to that in other dicotyledon plants. These findings provide the basis for the use of Arabidopsis thaliana as a model system to study the genetics, physiology and cell biology of wound healing and regenerative vascular tissue formation.     

Complexes of HLA-G protein on the cell surface are important for leukocyte Ig-like receptor-1 function

The nonclassical class I MHC molecule HLA-G is selectively expressed on extravillous cytotrophoblast cells at the maternal-fetal interface during pregnancy. HLA-G can inhibit the killing mediated by NK cells via interaction with the inhibitory NK cell receptor, leukocyte Ig-like receptor-1 (LIR-1). Comparison of the sequence of the HLA-G molecule to other class I MHC proteins revealed two unique cysteine residues located in positions 42 and 147. Mutating these cysteine residues resulted in a dramatic decrease in LIR-1 Ig binding. Accordingly, the mutated HLA-G transfectants were less effective in the inhibition of NK killing and RBL/LIR-1 induced serotonin release. Immunoprecipitation experiments demonstrated the involvement of the cysteine residues in the formation of HLA-G protein oligomers on the cell surface. The cysteine residue located at position 42 is shown to be critical for the expression of such complexes. These oligomers, unique among the class I MHC proteins, probably bind to LIR-1 with increased avidity, resulting in an enhanced inhibitory function of LIR-1 and an impaired killing function of NK cells.     

Bark structure and mode of canopy regeneration in trees of Melia azedarach L.

Summary The bark texture of Melia azedarach L. changes from smooth to furrowed as trees age. In trees that were cut down, those with smooth bark sprouted below the cut from suppressed buds; trees with thick, furrowed bark sprouted at the edge of the cut surface from adventitious buds. The trees that had thin, furrowed bark sprouted mainly at the edge of the cut from adventitious buds, but sometimes also from suppressed buds in cracks. The relationship between sprouting pattern and tree architecture are discussed.     

Effects of transgene expression of superoxide dismutase and glutathione peroxidase on pulmonary epithelial cell growth in hyperoxia

Prolonged exposure to supraphysiological oxygen concentrations results in the generation of reactive oxygen species, which can cause significant lung injury in critically ill patients. Supplementation with human recombinant antioxidant enzymes (AOE) may mitigate hyperoxic lung injury, but it is unclear which combination and concentration will optimally protect pulmonary epithelial cells. First, stable cell lines were generated in alveolar epithelial cells (MLE12) overexpressing one or more of the following AOE: Mn superoxide dismutase (MnSOD), CuZnSOD, or glutathione peroxidase 1. Next, A549 cells were transduced with 50-300 particles/cell of recombinant adenovirus containing either LacZ or each of the three AOE (alone or in combination). Cells were then exposed to 95% O(2) for up to 3 days, with cell number and viability determined daily. Overexpression of either MnSOD (primarily mitochondrial) or CuZnSOD (primarily cytosolic) reversed the growth inhibitory effects of hyperoxia within the first 48 h of exposure, resulting in a significant increase in viable cells (P < 0.05), with 1.5- to 3-fold increases in activity providing optimal protection. Protection from mitochondrial oxidation was confirmed by assessing aconitase activity, which was significantly improved in cells overexpressing MnSOD (P < 0.05). Data indicate that optimal protection from hyperoxic injury occurs in cells coexpressing MnSOD and glutathione peroxidase 1, with prevention of mitochondrial oxidation being a critical factor. This has important implications for clinical trials in preterm infants receiving SOD supplementation to prevent acute and chronic lung injury.     

The CD85J/leukocyte inhibitory receptor-1 distinguishes between conformed and beta 2-microglobulin-free HLA-G molecules

For a proper development of the placenta, maternal NK cells should not attack the fetal extravillous cytotrophoblast cells. This inhibition of maternal NK cells is partially mediated via the nonclassical MHC class I molecule HLA-G. Recently, we demonstrated that HLA-G forms disulfide-linked high molecular complexes on the surface of transfected cells. In the present study, we demonstrate that HLA-G must associate with beta(2)m for its interaction with CD85J/leukocyte Ig-like receptor-1 (LIR-1). Although HLA-G free H chain complexes are expressed on the surface, they are not recognized and possibly interfere with CD85J/LIR-1 and HLA-G interaction. The formation of these complexes on the cell surface might represent a novel mechanism developed specifically by the HLA-G protein aimed to control the efficiency of the CD85J/LIR-1-mediated inhibition. We also show that endogenous HLA-G complexes are expressed on the cell surface. These findings provide novel insights into the delicate interaction between extravillous cytotrophoblast cells and NK cells in the decidua.     

Terminology for plant polarity: Progress and difficulties

The recent attempts to establish a “natural” terminology for plant polarity^1–3 are significant as they have identified various problems in the classic terminology of polarity,⁴ and arrived at a logical and simple terminology (shootward and rootward).³ The related issue of polarity changes was also addressed while assuming that cell polarity is conserved throughout the development.²Key words: auxin, axiality, development, differentiation, epiphylly, plant architectureWhile the shootward and rootward terminology is very appealing and seems to describe “normal” plant development precisely, like in the model plant Arabidopsis thaliana, there are many instances in vascular plants that only partly fit the suggested terminology. I demonstrate it by describing three types of common rootward-shootward polarity changes in mature Angiosperm plants (out of a longer list), which are not solved by the new terminology.

1. Epiphylly of plantlets with roots formed on the margins of young leaves in Bryophyllum and other taxa.⁵ These roots result in a mixed polarity. For instance, the lower stem parts that had for a while only one rootward polarity acquire two contrasting directions of rootward polarity following the formation of many plantlet roots on leaf margins. Similarly, for the original roots, the young shoot was initially purely shootward but become at least partly of rootward polarity because of the formation of new plantlet roots on the leaves. Thus, in such plants a situation of rootward and shootward polarities originating from the same direction is found.
2. Aerial roots of many trees, e.g., of many Ficus species.⁵ These roots, which sometimes become larger than the original root system, must influence polarity to a large extent as discussed in the above example of much smaller roots.
3. Shoots emerging from roots of Populus, Rubus and many other taxa.⁵ Such shoots, formed at the rootward position relative to the root parts positioned closer to the original shoot, greatly alter the polarity status of the plants. They result in shootward and rootward polarities arriving from the same direction. Since many such shoots may develop along the root system, they result in an increasing complication of a mosaic of rootward and shootward polarities.

For all three above cases there is no data about where these opposite polarities meet, how they interact, and if there are physiological or developmental consequences to their signal cross-talk.I conclude that while the new shootward and rootward terminology³ is perfect in many cases throughout a plant''s life cycle and for practically all young vascular plants. However, this terminology needs some modifications or additions to fit other developmental situation found in many thousands of species that naturally or even artificially form ectopic roots or shoots. I therefore propose to distinguish between primary, secondary, tertiary and so on, ranks of shootward and rootward polarities.