Biomedical subjects

Uwe Niesner

Publications and source records attributed to Uwe Niesner.

5 recordsLinked to original sources

PubMed2005

A critical control element for interleukin-4 memory expression in T helper lymphocytes.

Naive T helper (Th) lymphocytes are induced to express the il4 (interleukin-4) gene by simultaneous signaling through the T cell receptor and the interleukin (IL)-4 receptor. Upon restimulation with antigen, such preactivated Th lymphocytes can reexpress the il4 gene independent of IL-4 receptor signaling. This memory for expression of the il4 gene depends on epigenetic modification of the il4 gene locus and an increased expression of GATA-3, the key transcription factor for Th2 differentiation. Here, we have identified a phylogenetically conserved sequence, the conserved intronic regulatory element, in the first intron of the il4 gene containing a tandem GATA-3 binding site. We show that GATA-3 binds to this sequence in a position- and orientation-dependent manner, in vitro and in vivo. DNA demethylation and histone acetylation of this region occurs early and selectively in differentiating, IL-4-secreting Th2 lymphocytes. Deletion of the conserved element by replacement of the first exon and part of the first intron of the il4 gene with gfp leads to a defect in the establishment of memory for expression of IL-4, in that reexpression of IL-4 still requires costimulation by exogenous IL-4. The conserved intronic regulatory element thus links the initial epigenetic modification of the il4 gene to GATA-3 and serves as a genetic control element for memory expression of IL-4.

Animals↗

PubMed2004

GATA-3 in human T cell helper type 2 development.

The delineation of the in vivo role of GATA-3 in human T cell differentiation is a critical step in the understanding of molecular mechanisms directing human immune responses. We examined T cell differentiation and T cell-mediated effector functions in individuals lacking one functional GATA-3 allele. CD4 T cells from GATA-3+/- individuals expressed significantly reduced levels of GATA-3, associated with markedly decreased T helper cell (Th)2 frequencies in vivo and in vitro. Moreover, Th2 cell-mediated effector functions, as assessed by serum levels of Th2-dependent immunoglobulins (Igs; IgG4, IgE), were dramatically decreased, whereas the Th1-dependent IgG1 was elevated compared with GATA-3+/+ controls. Concordant with these data, silencing of GATA-3 in GATA-3+/+ CD4 T cells with small interfering RNA significantly reduced Th2 cell differentiation. Moreover, GATA-3 mRNA levels increased under Th2-inducing conditions and decreased under Th1-inducing conditions. Taken together, the data strongly suggest that GATA-3 is an important transcription factor in regulating human Th2 cell differentiation in vivo.

Adolescent↗

PubMed2004

Developmental stage, phenotype, and migration distinguish naive- and effector/memory-like CD4+ regulatory T cells.

Regulatory T cells (Tregs) fulfill a central role in immune regulation. We reported previously that the integrin alphaEbeta7 discriminates distinct subsets of murine CD4+ regulatory T cells. Use of this marker has now helped to unravel a fundamental dichotomy among regulatory T cells. alphaE-CD25+ cells expressed L-selectin and CCR7, enabling recirculation through lymphoid tissues. In contrast, alphaE -positive subsets (CD25+ and CD25-) displayed an effector/memory phenotype expressing high levels of E/P-selectin-binding ligands, multiple adhesion molecules as well as receptors for inflammatory chemokines, allowing efficient migration into inflamed sites. Accordingly, alphaE -expressing cells were found to be the most potent suppressors of inflammatory processes in disease models such as antigen-induced arthritis.

Animals↗

PubMed2002

Tumor-targeting properties of antibody-vascular endothelial growth factor fusion proteins.

A major problem of antibody-based targeting of solid tumors is the poor penetration of antibodies into tumor tissue. Vasoactive immunoconjugates have been proposed as a means of increasing antibody uptake in tumors. In principle, VEGF (also known as vascular permeability factor) could selectively alter vascular permeability, leading to improved tumor targeting. A possible role for VEGF in the targeting of tumor neovasculature has been postulated, based on the overexpression of VEGF receptors in tumor endothelial cells. However, quantitative biodistribution studies on this topic are not available. In this report, we describe the cloning, expression, characterization and biodistribution in tumor-bearing mice of antibodies fused to either VEGF(120) or VEGF(164) The MAb fragments chosen for analysis were scFv(L19), specific for the ED-B domain of fibronectin, a marker of angiogenesis, and scFv(HyHEL-10), a negative control antibody of irrelevant specificity in mice. Neither unconjugated VEGF nor scFv(HyHEL-10)-VEGF fusion proteins showed accumulation in the tumor (tumor:blood ratios approx. 1 at 4 hr and 24 hr postinjection). By contrast, scFv(L19)-VEGF(120) but not scFv(L19)-VEGF(164) showed significant accumulation in tumors (tumor:blood ratio = 9.3 at 24 hr) but was not superior to unconjugated scFv(L19). Preinjection of unlabeled scFv(L19)-VEGF(120) prior to administration of radiolabeled fusion protein led to increased accumulation of radiolabeled scFv(L19)-VEGF(120) in the tumor but only at very high concentrations (20 microg/mouse).

Animals↗

PubMedDate not supplied

Quantitation of the tumor-targeting properties of antibody fragments conjugated to cell-permeating HIV-1 TAT peptides.

Human monoclonal antibodies are promising agents for the development of more selective anticancer therapeutics. However, the tumor-targeting efficiency of most anticancer antibodies is severely limited by their poor penetration into the tumor mass. Recent studies have shown that a peptide derived from the HIV TAT protein could improve the distribution of cytoplasmic reporter proteins when administered systemically as fusion proteins or cross-linked chimeras. In this article, we tested by quantitative biodistribtution analysis whether conjugation to TAT peptides could improve the tumor targeting properties of scFv(L19)-Cys: an engineered human antibody fragment specific for the ED-B domain of fibronectin, a marker located in the modified extracellular matrix surrounding tumor neovasculature. Our results show that TAT peptides, consisting either of L-amino acids or D-amino acids, can efficiently transduce target cells when conjugated to fluorophores and/or antibody fragments, suggesting a receptor-independent cell entry mechanism. However, conjugation of scFv(L19)-Cys to TAT peptides resulted in a severely reduced tumor targeting performance compared to the unconjugated antibody, as measured in murine F9 teratocarcinoma-bearing mice, after intravenous injection of the radiolabeled antibody preparations. Our results outline the usefulness of TAT peptides for the efficient in vitro transduction of cells with globular proteins. In particular, the use of TAT peptides composed of D-amino acids may significantly reduce proteolytic degradation. At the same time, the poor biodistribution properties of antibody-TAT conjugates cast doubts over the applicability of this methodology for the delivery of biopharmaceuticals in vivo.

Animals↗