Dendritic cells (DC) are unique in their ability to stimulate naive T cells to proliferate and to differentiate into effector T cells. DC, however, can also inhibit T cell activation and play a role in central and peripheral tolerance. IL-10 has been shown to render DC tolerogenic by unknown mechanisms. Using a combined monoclonal antibody/retroviral expression cloning approach, we show here that the inhibitory receptor LIR-2 (leukocyte immunoglobulinlike receptor-2, CD85d) is specifically up-regulated by IL-10 on maturing human DC. LPSstimulated, LIR-2-transfected DC inhibited the proliferation of T cells in autologous, as well as allogeneic culture systems in vitro. In addition, overexpression of LIR-2 on resting T cells, which lack LIR-2 expression, inhibited T cell proliferation induced by TCR activation. A novel soluble form of LIR-2 was detected in culture supernatants of maturing DC. IL-10 treatment of DC potently inhibited the production of soluble LIR-2. Recombinant soluble LIR-2 was able to completely restore the proliferation of T cells activated with LPS-plus IL-10-treated DC. Thus, IL-10 renders DC hypostimulatory by up-regulating cell surface LIR-2 and by inhibiting soluble LIR-2 in vitro.

Inflammatory bowel disease (IBD) comprises the two disorders ulcerative colitis (UC) and Crohn's disease (CD). Although the etiology is still unclear, initiation and aggravation of the inflammatory processes seem to be due to a massive local mucosal immune response. An increased number of greatly activated macrophages seems to contribute to the onset of IBD by expressing upregulated costimulatory molecules (e.g., CD80/CD86) and a cytokine profile favouring a type I proinflammatory response. The release of interleukin 2 (IL-2) and Interferon-gamma (IFN-gamma) by naive T lymphocytes predominantly stimulates cytotoxic T lymphocytes, macrophages, and natural killer (NK) cells and increases the antigen-presenting potential of all these cell types. Opposite this proinflammatory immune reaction a compensatory type II antiinflammatory response has been suggested in the inflamed mucosa, involving mainly interleukin 4 and interleukin 10. Both cytokines are able to down-regulate inflammatory mediators including tumor necrosis factor-alpha (TNF-alpha) and interleukin 1 and favor a humoral immune response. The main goal of this clinical trial is the local liposome-mediated gene transfer of these two antiinflammatory cytokines, interleukin 4 and interleukin 10, in patients with severe IBD of the rectum. This local administration of antiinflammatory cytokines will avoid toxic systemic side effects, prevents blocking of the beneficial effects of proinflammatory cytokines, e.g., TNF-alpha in other tissue compartments and increases the local concentration of interleukin 4 and interleukin 10 over a prolonged period of time. The combined effects of IL-4 and IL-10 have been shown to shift the Th1/Th2 cell activation in favor of a Th2 immune response which seems to be essential for fighting against the inflammation and ultimative healing.

Systemic anti-cytokine therapies have been unsuccessful in preventing mortality from gram-negative bacteremia in humans partly because of the failure to neutralize pro-inflammatory cytokines at sites of exaggerated production. In an attempt to deliver anti-inflammatory cytokines to organs directly, gene transfer was employed. Thirty-six BALB/c mice were injected intraperitoneally with cationic liposomes containing plasmids encoding the human interleukin-4 (hIL-4) or IL-13 gene. Both, hIL-4 and hIL-13 mRNA were detected by reverse transcription-polymerase chain reaction analysis in the liver and the spleen of the animals. Fourty-eight hours after the in vivo gene transfer, these 36 mice and 18 mock-transfected mice, were challenged with a lethal dose of E. coli lipopolysaccharide with D-galactosamine (D-GalN). Gene transfer with hIL-4 reduced the serum tumor necrosis factor (TNF)-alpha production in response to endotoxin/D-GalN by 80% from 113.1 pg/ml in mock-transfected animals to 22.2 pg/ml (p < 0.05); human IL-13 gene transfer reduced serum TNF-alpha levels by 90% (113.1 pg/ml to 11.6 pg/ml; p < 0.05). Survival was improved from 20% to over 83% in both treatment groups (p < 0.001). Our data demonstrate a potent in vivo anti-inflammatory action of both IL-4 and IL-13. In addition, the immune functions of peritoneal macrophages are significantly ameliorated in both treatment groups, with IL-13 demonstrating better macrophage immune modulation than IL-4 (p < 0.05).

Systemic anti-cytokine therapies have been unsuccessful in preventing mortality from gram-negative bacteremia in humans partly because of the failure to neutralize pro-inflammatory cytokines at sites of exaggerated production. In an attempt to deliver anti-inflammatory cytokines to organs directly, gene transfer was employed. Thirty-six BALB/c mice were injected intraperitoneally with cationic liposomes containing plasmids encoding the human interleukin-4 (hIL-4) or IL-13 gene. Both, hIL-4 and hIL-13 mRNA were detected by reverse transcription-polymerase chain reaction analysis in the liver and the spleen of the animals. Fourty-eight hours after the in vivo gene transfer, these 36 mice and 18 mock-transfected mice, were challenged with a lethal dose of E. coli lipopolysaccharide with D-galactosamine (D-GalN). Gene transfer with hIL-4 reduced the serum tumor necrosis factor (TNF)-alpha production in response to endotoxin/D-GalN by 80% from 113.1 pg/ml in mock-transfected animals to 22.2 pg/ml (p < 0.05); human IL-13 gene transfer reduced serum TNF-alpha levels by 90% (113.1 pg/ml to 11.6 pg/ml; p < 0.05). Survival was improved from 20% to over 83% in both treatment groups (p < 0.001). Our data demonstrate a potent in vivo anti-inflammatory action of both IL-4 and IL-13. In addition, the immune functions of peritoneal macrophages are significantly ameliorated in both treatment groups, with IL-13 demonstrating better macrophage immune modulation than IL-4 (p < 0.05).

Decreased production of T helper type 1 (Th1) cytokines, such as interferon-gamma (IFN-gamma) or interleukin-2 (IL-2), is a hallmark of atopic diseases. While accessory signals from antigen-presenting cells may be missing, T cells themselves may be suppressed in their ability to produce substantial amounts of Th1 cytokines. We show, in this study, that T cell receptor (TCR)-activated T cells from atopic dermatitis (AD) patients proliferate less than control T cells and produce lower amounts of IFN-gamma and IL-2, but comparable amounts of IL-4. Because mice lacking the nuclear factor kappa B (NF-kappaB) transcription factors - p65 or c-Rel - show reduced Th1, but undisturbed Th2 responses, we investigated the role of c-Rel and p65 for Th1 cytokine production in T cells from healthy and severe AD patients. TCR-activated primary T cells from healthy donors treated with c-Rel antisense oligonucleotides produced lower levels of IL-2 and IFN-gamma and proliferated less efficiently than the corresponding control T cells. Moreover, transfection of primary T cells with c-Rel or p65 enhanced proliferation and production of IL-2 and IFN-gamma. Nuclear extracts of activated primary T cells from AD donors bound weakly to NF-kappaB-specific oligonucleotides, compared to extracts from healthy control T cells. Western blotting studies revealed that nuclear, but not cytosolic, extracts from T cells of AD patients lacked significant amounts of c-Rel and p65. T cell clones derived from AD patients failed to sufficiently translocate c-Rel and p65 into the nucleus following activation. Thus, impaired nuclear translocation of c-Rel and p65 may determine an impaired Th1 cytokine response in AD.

Interleukin-4 (IL-4) is the major factor promoting the development of T helper type 2 (Th2) cells from naive precursor T cells. Minute amounts of IL-4 produced by naive T cells seem to be sufficient; however, the molecular mechanisms explaining this efficient utilization of are not yet known. Here, we show that human CD4 + CD45RA + naive T cells, in contrast to CD4 + CD45R0 + effector T cells, show responsiveness to endogenous as well as exogenous IL-4 to proliferate and differentiate towards Th2 cells in vitro. Despite production levels of IL-4 below conventional detection limits, CD45RA + T cell-derived IL-4 could clearly activate STAT6. Although the expression levels of IL-4R and STAT6 were not different between naive and effector T cells, only naive T cells responded to IL-4 in a STAT6-dependent reporter gene assay. Transfecting a trans-dominant negative form of STAT6 abrogated IL-4-induced proliferation in CD45RA + cells. A significantly higher protein tyrosine phosphatase (PTPase) activity was detected in CD45R0 + T cells as compared to CD45RA + T cells. Cross-linking CD45 potently reduced PTPase activity in CD45R0 + T cells and restored their ability to proliferate in response to IL-4. Thus, CD45 PTPase activity contributes to the susceptibility of naive and memory T cells to respond to IL-4.