Regulatory T cells (Tregs) fulfill a central role in immune regulation. We reported previously that the integrin αEβ7 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. αE −CD25+ cells expressed L-selectin and CCR7, enabling recirculation through lymphoid tissues. In contrast, αE-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, αE-expressing cells were found to be the most potent suppressors of inflammatory processes in disease models such as antigen-induced arthritis.

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The basic helix-loop-helix transcriptional repressor twist1, as an antagonist of nuclear factor κB (NF-κB)–dependent cytokine expression, is involved in the regulation of inflammation-induced immunopathology. We show that twist1 is expressed by activated T helper (Th) 1 effector memory (EM) cells. Induction of twist1 in Th cells depended on NF-κB, nuclear factor of activated T cells (NFAT), and interleukin (IL)-12 signaling via signal transducer and activator of transcription (STAT) 4. Expression of twist1 was transient after T cell receptor engagement, and increased upon repeated stimulation of Th1 cells. Imprinting for enhanced twist1 expression was characteristic of repeatedly restimulated EM Th cells, and thus of the pathogenic memory Th cells characteristic of chronic inflammation. Th lymphocytes from the inflamed joint or gut tissue of patients with rheumatic diseases, Crohn's disease or ulcerative colitis expressed high levels of twist1. Expression of twist1 in Th1 lymphocytes limited the expression of the cytokines interferon-γ, IL-2, and tumor necrosis factor-α, and ameliorated Th1-mediated immunopathology in delayed-type hypersensitivity and antigen-induced arthritis.

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.

In Th1 and Th2 memory lymphocytes, the genes for the cytokines interleukin (IL)‐4 and interferon‐γ (IFN‐γ) are imprinted for expression upon restimulation. This cytokine memory is based on expression of the transcription factors T‐bet for IFN‐γ, and GATA‐3 for IL‐4, and epigenetic modification of the cytokine genes. In Th2 cells, expression of the cytokine IL‐10 is also induced by GATA‐3. Here, we show that this induction is initially not accompanied by epigenetic modification of the IL‐10 gene. Only after repeated restimulation of a memory Th2 cell in the presence of IL‐4, extensive histone acetylation of the IL‐10 gene is detectable. This epigenetic imprinting correlates with the development of a memory for IL‐10 in repeatedly restimulated Th2 cells. In Th1 cells, IL‐10 expression is induced by IL‐12, but the IL‐10 gene lacks detectable histone acetylation. Accordingly, IL‐10 expression in restimulated memory Th1 cells remains conditional on the presence of IL‐12. This finding defines a potential anti‐inflammatory role for IL‐12 in Th1 recall responses. While in primary Th1 responses IL‐12 is required to induce expression of the pro‐inflammatory cytokine IFN‐γ, in secondary Th1 responses IFN‐γ re‐expression is independent of IL‐12, which still is able to induce expression of the anti‐inflammatory cytokine IL‐10.