We have characterized the progressive stages of chronic intestinal inflammation that develops spontaneously in specific pathogen-free (SPF) mice with a targeted disruption in the IL-10 gene (IL-10 Ϫ / Ϫ ). Our longitudinal studies showed that inflammatory changes first appear in the cecum, ascending and transverse colon of 3-wk-old mutants. As the disease progressed, lesions appeared in the remainder of the colon and in the rectum. Some aged IL-10 Ϫ / Ϫ mice also developed inflammation in the small intestine. Prolonged disease with transmural lesions and a high incidence of colorectal adenocarcinomas (60%) was observed in 6-mo-old mutants. Mechanistic studies have associated uncontrolled cytokine production by activated macrophages and CD4

SummaryMice rendered deficient in the production of interleukin 10 (IL-10 -/-) develop a chronic inflammatory bowel disease (IBD) that predominates in the colon and shares histopathological features with human IBD. Our aim was to identify which cell type(s) can mediate colitis in IL-10 -/-mice. We detected an influx ofimmunoglobulin-positive cells into the colon and the presence of colon-reactive antibodies in the serum of IL-10 -/-mice. To assess a pathogenic role for B cells, we generated a B cell-deficient (B -/-) strain oflL-10 -/-mice. B-/-IL-10 -/-mice acquired a severe colitis analogous to that oflL-10 -/-mice, implying that B cells were not the primary mediator of IBD in this model. A series of cell transfer experiments was performed to assess a pathogenic role for T cells. When IL-10 -/-T cell-enriched lamina propria lymphocytes (LPL) or intraepithelial lymphocytes (IEL) were transferred into immunodeficient recombinase-activating gene (RAG)-2 -/-recipients, a mild to severe colitis developed, depending on the cell number transferred. Lymphocytes recovered from the colon of transplanted R.AG-2 -/-mice with colitis were predominantly otI~TCR+CD4 +, including a large proportion of CD4 § + cells. These cells were also CD45RB -/l~ and CD44 +, indicative of an activated/memory population. Individual populations of CD4+CD80~ -, CD4+CD8oe + and CD4-CD8ot + T cells were then isolated from the lamina propria compartment of IL-10 -/-mice and transferred into RAG-2 -/-recipients. Only IL-10 -/-CD4-expressing LPL, including both the CD4+CD8ot -and CD4+CD8r + populations, induced colitis in recipient mice. Interferon-',/, but little to no IL-4, was produced by CD4+CD8o~ -and CD4+CD8ot § LPL recovered from the inflamed colons of RAG-2 -/-recipients implicating a T helper cell 1 (TH1)-mediated response. We thus conclude that colitis in IL-10 -/-mice is predominantly mediated by THl-type cll3TCtk + T cells expressing CD4 alone, or in combination with the CD8ct molecule.

SummaryWe have characterized the mast cell stimulating activity of murine cytokine synthesis inhibitory factor, referred to as interleukin 10 (IWO). It was found that IL10 alone failed to support the growth of mast cell lines and mast cell progenitors. Nevertheless, it dramatically enhanced their growth when combined with IL3 or IL4. Moreover, IL4 plus IL10 supported the proliferation of mast cells as well as IL-3, suggesting that these two factors may provide a pathway for their development independent of IL3. However, optimal mast cell growth was stimulated by the combination of 11,10, 114, and IL3. This particular set of cytokines are coordinately produced by activated T cells and may constitute an effective network regulating early and late stages of mast cell development during certain immune responses.

We evaluated human CD8 ؉ T-cell responses generated by targeting antigens to dendritic cells (DCs) through various lectin receptors. We found the immunoreceptor tyrosine-based inhibitory motifcontaining DC immunoreceptor (DCIR) to mediate potent cross-presentation. A single exposure to a low dose of anti-DCIR-antigen conjugate initiated antigenspecific CD8 ؉ T-cell immunity by all human DC subsets including ex vivogenerated DCs, skin-isolated Langerhans cells, and blood myeloid DCs and plasma-

IntroductionChronic diseases such as cancer and viral infections have long resisted the development of effective therapeutic vaccines. It is currently thought that such vaccines will need to effectively harness dendritic cells (DCs) to induce specific and long-lasting cellular immunity, in particular cytotoxic T cells of higher potency. 1,2 Therefore, understanding the combination of signals that promote activation, proliferation, differentiation, and survival of effector CD8 ϩ T cells is crucial for the development of such vaccines. [3][4][5] The immunologic synapse is formed between a T cell and an antigen presenting cell (APC) and delivers a unique combination of signals that ultimately shape the type and strength of the T-cell response. 6 Ag dose, costimulatory molecules, and cytokines can all direct the fate of naive T-cell differentiation to mature effector cells. 7-10 IL-12 and IFN-␣, as well as the costimulatory molecules CD70 and 4-1BBL, for example, regulate and fine-tune the magnitude and duration of the effector CD8 ϩ T-cell response, as well as the nature of the elicited memory T-cell population within the immunologic synapse. 11 The diverse subpopulations of DCs provide the differential composition of molecules and receptors that allows for a specialized immune response to occur. 12-15 Indeed, as we have reported, Langerhans cells (LCs) are potent activators of naive CD8 ϩ T cells compared with dermal CD14 ϩ DCs. 16 Dermal CD1a ϩ DCs show an intermediate activity and are able to induce effector CD8 ϩ T-cell differentiation, although not as robustly as do LCs. 16 We sought to examine the role of the epidermal and dermal DC subset-specific cytokines IL-15 and IL-10 in the differential capacity to induce CD8 ϩ T-cell responses. [16][17][18] In humans, IL-15-differentiated DCs are particularly efficient at priming melanomaspecific CD8 ϩ T cells into CTLs. 19,20 In contrast, IL-10-treated DCs were shown to induce anergic CD8 ϩ T-cell responses. 21,22 Given their unique cytokine expression profile and their differential ability to prime effector CD8 ϩ T cells, we assessed the direct contribution of skin DC-specific cytokines to the quality of a primary CD8 ϩ T-cell response. Methods DC subsetsIn vitro DC subsets were differentiated from CD34 ϩ hematopoietic progenitor cells that were isolated from the blood of G-CSF-mobilized healthy volunteers. Hematopoietic progenitor cells were cultured at 0.5 ϫ 10 6 cells/mL in Yssel medium (Irvine Scientific) supplemented with 5% autologous serum, 50M ␤-mercaptoethanol, 1% L-glutamine, 1% penicillin/streptomycin, GM-CSF (50 ng/mL; Genzyme), Flt3-L (100 ng/ mL; R&D Systems), and TNF-␣ (10 ng/mL; R&D Systems) for 9 days. Media and cytokines were refreshed at day 5 of culture. Subsets of DCs, CD1a ϩ CD14 Ϫ (in vitro LCs) and CD1a Ϫ CD14 ϩ DCs (in vitro CD14 ϩ DCs) were then purified by cell sorting after staining with anti-CD1a FITC (Dako) and anti-CD14 APC mAbs (Invitrogen), yielding a purity of 95%-99%.Epidermal LCs, dermal CD1a ϩ DCs, and dermal CD14 ϩ DCs were puri...