Mucosal T lymphocyte numbers are selectively reduced in integrin alpha E (CD103)-deficient mice.

The mucosal lymphocyte integrin alpha E(CD103)beta 7 is thought to be important for intraepithelial lymphocyte (IEL) localization or function. We cloned the murine integrin gene encoding alpha E, localized it to chromosome 11, and generated integrin alpha E-deficient mice. In alpha E-/- mice, intestinal and vaginal IEL numbers were reduced, consistent with the known binding of alpha E beta 7 to E-cadherin expressed on epithelial cells. However, it was surprising that lamina propria T lymphocyte numbers were diminished, as E-cadherin is not expressed in the lamina propria. In contrast, peribronchial, intrapulmonary, Peyer's patch, and splenic T lymphocyte numbers were not reduced in alpha E-deficient mice. Thus, alpha E beta 7 was important for generating or maintaining the gut and vaginal T lymphocytes located diffusely within the epithelium or lamina propria but not for generating the gut-associated organized lymphoid tissues. Finally, the impact of alpha E deficiency upon intestinal IEL numbers was greater at 3-4 wk of life than in younger animals, and affected the TCR alpha beta+ CD8+ T cells more than the gamma delta T cells or the TCR alpha beta+ CD4+CD8- population. These findings suggest that alpha E beta 7 is involved in the expansion/recruitment of TCR alpha beta+ CD8+ IEL following microbial colonization. Integrin alpha E-deficient mice will provide an important tool for studying the role of alpha E beta 7 and of alpha E beta 7-expressing mucosal T lymphocytes in vivo.     

The mechanism of a defective IFN-gamma response to bacterial toxins in an atopic dermatitis model, NC/Nga mice, and the therapeutic effect of IFN-gamma, IL-12, or IL-18 on dermatitis

NC/Nga (NC) mice raised under conventional conditions (Conv. NC mice) spontaneously develop dermatitis similar to human atopic dermatitis, whereas NC mice raised under the specific pathogen-free conditions do not develop dermatitis. In the present study, we show that the representative Th1 cytokine, IFN-gamma levels in the sera of NC mice, injected with either staphylococcal enterotoxin B or endotoxin (LPS), to be severalfold lower than those of normal mice. The low IFN-gamma response to staphylococcal enterotoxin B was correlated to the lack of regular Vbeta8(+) T cells and Vbeta8(+) NK T cells, and the low IFN-gamma response to LPS was correlated to an impaired IL-18 production of macrophages. The CD3-stimulated IL-4 production from liver and spleen T cells from Conv. NC mice in vitro was greatly augmented. The serum IL-4 levels of untreated Conv. NC mice also were higher than those of normal mice and specific pathogen-free NC mice. Treatment of Conv. NC mice either with IFN-gamma, IL-12, or IL-18 twice a week from 4 wk of age substantially inhibited the elevation of the serum IgE levels, serum IL-4 levels, and dermatitis, and IL-12 or IL-18 treatment also reduced the in vitro IL-4 production from CD3-stimulated liver T cells. The systemic deficiency in the Th1 response to bacterial stimulation thus leads to a Th2-dominant state and may induce an abnormal cellular immune response in the skin accompanied with an overproduction of IgE and a susceptibility to dermatitis in NC mice.     

CD4+ T cell-associated pathophysiology critically depends on CD18 gene dose effects in a murine model of psoriasis

In a CD18 hypomorphic polygenic PL/J mouse model, the severe reduction of CD18 (beta(2) integrin) to 2-16% of wild-type levels leads to the development of a psoriasiform skin disease. In this study, we analyzed the influence of reduced CD18 gene expression on T cell function, and its contribution to the pathogenesis of this disease. Both CD4(+) and CD8(+) T cells were significantly increased in the skin of affected CD18 hypomorphic mice. But only depletion of CD4(+) T cells, and not the removal of CD8(+) T cells, resulted in a complete clearance of the psoriasiform dermatitis. This indicates a central role of CD4(+) T cells in the pathogenesis of this disorder, further supported by the detection of several Th1-like cytokines released predominantly by CD4(+) T cells. In contrast to the CD18 hypomorphic mice, CD18 null mutants of the same strain did not develop the psoriasiform dermatitis. This is in part due to a lack of T cell emigration from dermal blood vessels, as experimental allergic contact dermatitis could be induced in CD18 hypomorphic and wild-type mice, but not in CD18 null mutants. Hence, 2-16% of CD18 gene expression is obviously sufficient for T cell emigration driving the inflammatory phenotype in CD18 hypomorphic mice. Our data suggest that the pathogenic involvement of CD4(+) T cells depends on a gene dose effect with a reduced expression of the CD18 protein in PL/J mice. This murine inflammatory skin model may also have relevance for human polygenic inflammatory diseases.     

Administration of mAb against alpha E beta 7 prevents and ameliorates immunization-induced colitis in IL-2-/- mice

We previously demonstrated that 2,4,6-trinitrophenol (TNP)-OVA immunization leads to a transmural colitis in the IL-2-/- mouse that is caused by IL-12-driven CD4+ Th1 T cells and resembles human Crohn's disease. The integrin alpha E beta 7 is highly expressed on colonic intraepithelial lymphocytes and has been suggested to function as a homing or retention molecule for intraepithelial lymphocytes. To evaluate the role of alpha E beta 7 in colitis, we administered a mAb against alpha E beta 7 to IL-2-/- mice that were immunized at the same time with TNP-OVA in CFA. To our surprise, this treatment resulted in a significantly reduced colitis severity score, 0-2 vs 3-4, that was associated with a significant reduction in CD4+ lamina propria lymphocyte subpopulation (p < 0.01). In contrast, the total number of splenic CD4+ T cells of treated animals was significantly elevated compared with that of untreated animals (3.2 +/- 0.6 x 107 vs 1.2 +/- 0.2 x 107; p < 0.05). Similarly, functional studies revealed that IFN-gamma production by lamina propria lymphocytes isolated from IL-2-/- TNP-OVA-immunized mice treated with anti-alpha E beta 7 was significantly lower than in untreated IL-2-/- TNP-OVA-immunized mice. In contrast, IFN-gamma production by splenic cells isolated from treated IL-2-/- TNP-OVA-immunized mice was significantly higher than in untreated mice. Finally, TNP-OVA-immunized IL-2-/- mice that were treated after the colitis had been established also showed a significant decrease in mucosal inflammation after alpha E beta 7 mAb administration. Thus, the above findings demonstrate that the onset and maintenance of inflammatory bowel disease depends on the colonic localization of lamina propria CD4+ lymphocytes expressing alpha E beta 7.     

Vaccination without autoantigen protects against collagen II-induced arthritis via immune deviation and regulatory T cells

Anti-inflammation immunotherapy has been successfully applied for the treatment of autoimmune diseases. Mucosal vaccines against autoimmune disorders are beneficial by influencing the regulatory compartment of gut and systemic adaptive immune systems. A Salmonella vector expressing colonization factor Ag I (CFA/I), shown to behave as an anti-inflammatory vaccine, stimulates the production of CD4(+)CD25(+) T cells and regulatory cytokines. In this work, we queried whether Salmonella-CFA/I can protect DBA/1 mice from collagen-induced arthritis. The incidence of arthritis and cartilage loss in vaccinated DBA/1 mice was remarkably lower when compared with unprotected mice. Clinical findings were accompanied by the suppression of inflammatory cytokines TNF-alpha, IL-1beta, IL-6, and IL-27. Vaccination evoked a multi-tier response consisting of IL-4 producing Th2 cells, an increased production of TGF-beta by CD4(+) T cells, and suppression of collagen II-specific CD4(+) T cell proliferation. To assess the contribution of Salmonella-CFA/I-primed CD4(+) T cells, adoptive transfer studies with total CD4(+), CD4(+)CD25(-), or CD4(+)CD25(+) T cells were performed 15 days postchallenge. Mice receiving either subset showed reduced disease incidence and low clinical scores; however, mice receiving total CD4(+) T cells showed delayed disease onset by 10 days with reduced clinical scores, reduced IL-17 and IL-27, but enhanced IL-4, IL-10, IL-13, and TGF-beta. Inhibition of TGF-beta or IL-4 compromised protective immunity. These data show that Salmonella-CFA/I vaccination of DBA/1 mice protects against collagen-induced arthritis by stimulating TGF-beta- and IL-4-producing regulatory CD4(+) T cells.     

Human mast cell chymase cleaves pro-IL-18 and generates a novel and biologically active IL-18 fragment

Increased release of IL-18 in the skin causes atopic dermatitis (AD)-like skin lesions, suggesting a role of IL-18 in the pathogenesis of AD. Caspase-1 is a well-known activator of IL-18, but caspase-1 knockout mice still have biologically active IL-18. Normal human keratinocyte constitutively produces pro-IL-18, but it is unable to activate it, suggesting the existence of an alternative pathway for IL-18 in the skin. Dermal accumulation of mast cells is commonly observed in AD patients and in experimental mouse models of AD. Connective tissue mast cells contain high amounts of chymase and tryptase in their cytoplasmic granules. In the present study, we demonstrated that activation of IL-18 is a novel function of human mast cell chymase. Human mast cell chymase rapidly cleaves recombinant pro-IL-18 at 56-phenylalanine and produces a biologically active IL-18 fragment that is smaller than any other reported IL-18-derived species. The human mast cell chymase and the novel IL-18-derived active peptide may be novel therapeutic targets in AD- and IL-18-associated diseases.     

Differential regulation of the nature and functions of dendritic cells and macrophages by cathepsin E

The aspartic proteinase cathepsin E is localized mainly in the endosomal structures of APCs and has been implicated in a variety of immune responses, however, the precise roles of cathepsin E in these cells remain speculative. In this study, we report the effect of disrupting the gene encoding cathepsin E on the nature and functions of dendritic cells (DCs) and macrophages derived from mouse bone marrow precursors, as well as mouse peritoneal macrophages. Whereas cathepsin E deficiency induced the accumulation of the lysosome-associated membrane protein (LAMP)-1 and LAMP-2 and elevated the lysosomal pH in macrophages, it did not have these effects on DCs. Although cathepsin E deficiency also caused a marked decrease in degradation of phagocytosed OVA and chemotactic responses to MCP-1 and fMLP by macrophages, these abilities were little affected in DCs by the absence of cathepsin E. Interestingly, cathepsin E deficiency markedly decreased the ability of macrophages to present intact OVA, as well as an OVA-derived antigenic peptide (266-281), to cognate T cells, while that of DCs was inversely enhanced by the absence of this protein. This paradox was resolved, in part, by the enhanced phagocytic activity and the increased expression of the costimulatory molecules CD86, CD80, and CD40, which amplify the response of T cells, in cathepsin E-deficient DCs compared with the wild-type cells. These results indicate that cathepsin E differentially regulates the nature and function of DCs and macrophages.     

Development of atopic dermatitis-like skin lesions in STAT6-deficient NC/Nga mice

Atopic dermatitis (AD) is a pruritic inflammatory skin disease characterized by elevation of plasma levels of total IgE, infiltration of mast cells and eosinophils, and the expression of cytokines by Th2 T cells. However, the role of Th2 cells in the pathogenesis of AD is not fully understood. In this study we examined the NC/Nga (NC) mouse model of AD and established STAT6-deficient (SATA6(-/-)) NC mice to investigate the relevance of IL-4-mediated immune responses. Surprisingly, these mice elicited AD-like skin lesions at equivalent frequency and time of onset compared with normal NC littermates. Histological features of the lesion in STAT6(-/-) NC mice fulfilled the criteria for the pathogenesis of AD, although these mice fail to produce IgE and Th2 cytokines. The lymph nodes proximal to the regions of skin that developed lesions exhibited massive enlargement elicited by the accumulation of activated IFN-gamma-secreting T cells. Moreover, caspase I, IL-18, IL-12, and IFN-gamma are found to be highly expressed at the skin lesion, occurring simultaneously with elevation of eotaxin 2 and CCR3 expression. Therefore, the Th2-mediated immune response is not necessary for the development of AD-like skin disease in NC mice. The skin microenvironment that favored IFN-gamma production tightly correlates with the skin disease in NC mice through the infiltration of eosinophils.     

Heterogeneity of NK1.1+ T cells in the bone marrow: divergence from the thymus.

NK1.1+ T cells in the mouse thymus and bone marrow were compared because some marrow NK1.1+ T cells have been reported to be extrathymically derived. Almost all NK1.1+ T cells in the thymus were depleted in the CD1-/-, beta2m-/-, and Jalpha281-/- mice as compared with wild-type mice. CD8+NK1.1+ T cells were not clearly detected, even in the wild-type mice. In bone marrow from the wild-type mice, CD8+NK1.1+ T cells were easily detected, about twice as numerous as CD4+NK1.1+ T cells, and were similar in number to CD4-CD8-NK1.1+ T cells. All three marrow NK1.1+ T cell subsets were reduced about 4-fold in CD1-/- mice. No reduction was observed in CD8+NK1.1+ T cells in the bone marrow of Jalpha281-/- mice, but marrow CD8+NK1.1+ T cells were markedly depleted in beta2m-/- mice. All NK1.1+ T cell subsets in the marrow of wild-type mice produced high levels of IFN-gamma, IL-4, and IL-10. Although the numbers of marrow CD4-CD8-NK1.1+ T cells in beta2m-/- and Jalpha281-/- mice were similar to those in wild-type mice, these cells had a Th1-like pattern (high IFN-gamma, and low IL-4 and IL-10). In conclusion, the large majority of NK1.1+ T cells in the bone marrow are CD1 dependent. Marrow NK1.1+ T cells include CD8+, Valpha14-Jalpha281-, and beta2m-independent subsets that are not clearly detected in the thymus.     

Topical superantigen exposure induces epidermal accumulation of CD8+ T cells, a mixed Th1/Th2-type dermatitis and vigorous production of IgE antibodies in the murine model of atopic dermatitis

Patients with atopic dermatitis (AD) have repeated cutaneous exposure to both environmental allergens and superantigen-producing strains of Staphylococcus aureus. We used a murine model of AD to investigate the role of staphylococcal enterotoxin B (SEB) in the modulation of allergen-induced skin inflammation. Mice were topically exposed to SEB, OVA, a combination of OVA and SEB (OVA/SEB), or PBS. Topical SEB and OVA/SEB exposure induced epidermal accumulation of CD8+ T cells and TCRVbeta8+ cells in contrast to OVA application, which induced a mainly dermal infiltration of CD4+ cells. SEB and OVA/SEB exposure elicited a mixed Th1/Th2-associated cytokine and chemokine expression profile within the skin. Restimulation of lymph node cells from OVA- and OVA/SEB-exposed mice with OVA elicited strong production of IL-13 protein, whereas substantial amounts of IFN-gamma protein were detected after SEB stimulation of cells derived from SEB- or OVA/SEB-exposed mice. Topical SEB treatment elicited vigorous production of SEB-specific IgE and IgG2a Abs and significantly increased the production of OVA-specific IgE and IgG2a Abs. The present study shows that topical exposure to SEB provokes epidermal accumulation of CD8+ T cells, a mixed Th2/Th1 type dermatitis and vigorous production of specific IgE and IgG2a Abs, which can be related to the chronic phase of atopic skin inflammation.     

Age-associated decline in effective immune synapse formation of CD4(+) T cells is reversed by vitamin E supplementation

Aging is associated with reduced IL-2 production and T cell proliferation. Vitamin E supplementation, in aged animals and humans, increases cell division and IL-2 production by naive T cells. The immune synapse forms at the site of contact between a T cell and an APC and participates in T cell activation. We evaluated whether vitamin E affects the redistribution of signaling proteins to the immune synapse. Purified CD4(+) T cells, from the spleens of young and old mice, were treated with vitamin E before stimulation with a surrogate APC expressing anti-CD3. Using confocal fluorescent microscopy, we observed that CD4(+) T cells from old mice were significantly less likely to recruit signaling proteins to the immune synapse than cells from young mice. Vitamin E increased the percentage of old CD4(+) T cells capable of forming an effective immune synapse. Similar results were found following in vivo supplementation with vitamin E. When compared with memory cells, naive T cells from aged mice were more defective in immune synapse formation and were more responsive to vitamin E supplementation. These data show, for the first time, that vitamin E significantly improves age-related early T cell signaling events in naive CD4(+) T cells.     

Skin-infiltrating CD8+ T cells initiate atopic dermatitis lesions

Skin lesions in the allergic form of atopic dermatitis (AD) are induced by allergen-specific T cells that infiltrate the skin at the site of allergen exposure. Although Th2-type CD4+ T cells appear to be crucial in AD pathophysiology, little is known about the contribution of CD8+ T cells in the development of the allergic skin inflammation. In the present study, we have analyzed the respective role of CD8+ and CD4+ T cells in the development of AD skin lesions in a mouse model of allergen-induced AD. In sensitized mice, CD8+ T cells are rapidly and transiently recruited to the allergen-exposed site and initiate the inflammatory process leading to skin infiltration with eosinophils and Th1/Th2-producing cells. CD8+ T cell-depleted mice show no inflammation, demonstrating that these cells are mandatory for the development of AD. In contrast, CD4+ T cell-depleted mice develop a severe form of eczema. Furthermore, adoptive transfer of CD8+ T cells from sensitized mice into naive recipient mice leads to skin inflammation soon after allergen exposure. These data indicate that allergen-primed CD8+ T cells are required for the development of AD-like lesions in mice.     

Pyridone 6, a pan-JAK inhibitor, ameliorates allergic skin inflammation of NC/Nga mice via suppression of Th2 and enhancement of Th17

Atopic dermatitis (AD) is a common pruritic inflammatory disease triggered by a defective skin barrier and immunodysregulation. AD has been considered a typical example of a Th2 response associated with allergic disease. In the early phases of the disease, symptoms include IgE hyperproduction, eosinophil accumulation, and mast cell activation; in the chronic phase, a Th1-dominant immune response is also observed at the sites of AD skin lesions. The role of IL-17-producing Th (Th17) cells in AD has not been established. In the current study, we found that pyridone 6 (P6), a pan-JAK inhibitor, delayed the onset and reduced the magnitude of skin disease in an AD-like skin-disease model of NC/Nga mice. P6 reduced IFN-γ and IL-13, whereas it enhanced IL-17 and IL-22 expression. In vitro, P6 also inhibited both Th1 and Th2 development, whereas it promoted Th17 differentiation from naive T cells when present within a certain range of concentrations. This was probably because P6 strongly inhibited STAT1, STAT5, and STAT6 phosphorylation, whereas STAT3 phosphorylation was less efficiently suppressed by P6 at the same concentration. Furthermore, IL-22 protects keratinocytes from apoptosis induced by IFN-γ, and administration of IL-17 and IL-22 partially ameliorated skin diseases in NC/Nga mice. These results suggested that the JAK inhibitor P6 is therapeutic for AD by modulating the balance of Th2 and Th17.     

T cell-associated CD18 but not CD62L, ICAM-1, or PSGL-1 is required for the induction of chronic colitis

The induction and perpetuation of chronic colitis are thought to involve a complex set of adhesive interactions between T cells and endothelial cells located on the vasculature within secondary lymphoid tissue and the intestine. The objective of this study was to assess the roles of T cell-associated CD18, CD62L (L-selectin), ICAM-1, and P-selectin glycoprotein ligand-1 (PSGL-1) in the induction of chronic colitis in mice. CD4(+)CD25(-) T cells derived from either wild-type (WT), CD18-deficient [CD18 knockout (KO)], CD62L KO, ICAM-1 KO, or PSGL-1 KO mice were adoptively transferred into recombinase activating gene-1 (RAG-1)-deficient mice (RAG KO mice) to assess the potential of these T cells to induce chronic colitis. At 8-10 wk following T cell transfer, we observed moderate to severe colitis as assessed by increases in colon weight-to-length ratios and by blinded histopathological analysis. In contrast, we found that transfer of CD18 KO T cells into RAG KO recipients resulted in the significant attenuation of colonic inflammation in these mice. Furthermore, we observed fewer infiltrating CD4(+) T cells in the colonic lamina propria in the CD18 KO-->RAG KO group compared with the WT-->RAG KO group. Finally, message levels of colonic TNF-alpha, IL-1beta, and IFN-gamma were significantly reduced in CD18 KO-->RAG KO mice compared with colitic control animals. We conclude that T cell-associated CD18, but not CD62L, ICAM-1, or PSGL-1, is required for the development of chronic colitis.     

Cutaneous inflammatory disorder in integrin alphaE (CD103)-deficient mice

The integrin alpha(E)beta(7) is thought to play an important role in the localization of mucosal, but not of cutaneous T lymphocytes. Thus, it was surprising that 89% of adult alpha(E)(-/-) mice on the 129/Sv x BALB/c background developed inflammatory skin lesions without an apparent infectious etiology. Skin inflammation correlated with alpha(E) deficiency in mice with a mixed 129/Sv x BALB/c background, but not in mice further backcrossed to BALB/c and housed in a second animal facility. These studies suggested that alpha(E) deficiency, in combination with other genetic and/or environmental factors, is involved in lesion development. The lesions were infiltrated by CD4(+) T cells and neutrophils, and associated with increased expression of inflammatory cytokines. Furthermore, skin inflammation resulted from transfer of unfractionated alpha(E)(-/-) splenocytes into scid/scid mice, but not from transfer of wild-type splenocytes, suggesting that the lesions resulted from immune dysregulation. We also studied the role of alpha(E)beta(7) in a murine model of hyperproliferative inflammatory skin disorders that is induced by transfer of minor histocompatibility-mismatched CD4(+)/CD45RB(high) T cells into scid/scid mice under specific environmental conditions. Under housing conditions that were permissive for lesion development, transfer of alpha(E)-deficient CD4(+)/CD45RB(high) T cells significantly exacerbated the cutaneous lesions as compared with lesions observed in mice reconstituted with wild-type donor cells. These experiments suggested that alpha(E)-expressing cells play an important role during the course of cutaneous inflammation. In addition, they suggest that alpha(E)beta(7) deficiency, in combination with other genetic or environmental factors, is a risk factor for inflammatory skin disease.     

IL-7 enhances the responsiveness of human T cells that develop in the bone marrow of athymic mice

The beige/nude/xid/human (bnx/hu) model of human hematopoiesis provides a unique opportunity to study extrathymic human T lymphocyte development in an in vivo system. Purified human hematopoietic stem cells develop into mature T lymphocytes and immature progenitors in the bone marrow of athymic bnx mice. The human T cells are all TCR alpha beta(+) and display a restricted TCRV beta repertoire. In the current studies, we examined the effects of systemic human IL-7 (huIL-7) administration on the phenotype and the activation status of the bnx/hu T cells. In the majority of the mice that did not have huIL-7 administration, a higher frequency of human CD3(+)/CD8(+) than CD3(+)/CD4(+) T cells developed in the bone marrow. This phenomenon is also frequently observed in human bone marrow transplant recipients. Extremely low levels of IL-2 were expressed by human CD3(+) cells isolated from these mice, in response to PMA plus ionomycin and to CD3 and CD28 cross-linking. IL-4 was not expressed by cells exposed to either stimulus, demonstrating a profound inability of the bnx/hu T cells to produce this cytokine. Systemic production of huIL-7 from engineered stromal cells transplanted into the mice increased the human CD4 to CD8 ratios, and increased the ratio of memory to naive CD4(+) and CD8(+) T cells. The human CD3(+) cells recovered from mice that had systemic huIL-7 and equivalent numbers of CD3(+)/CD4(+) and CD3(+)/CD8(+) cells in the marrow were still unable to produce IL-4 in response to any condition tested, but were capable of normal levels of IL-2 production following stimulation.     

Protective effect of IL-18 on kainate- and IL-1 beta-induced cerebellar ataxia in mice

The pathogenesis of sporadic cerebellar ataxia remains unknown. In this study, we demonstrate that proinflammatory cytokines, IL-18 and IL-1beta, reciprocally regulate kainate-induced cerebellar ataxia in mice. We show that systemic administration of kainate activated IL-1beta and IL-18 predominantly in the cerebellum of mice, which was accompanied with ataxia. Mice deficient in caspase-1, IL-1R type I, or MyD88 were resistant to kainate-induced ataxia, while IL-18- or IL-18R alpha-deficient mice displayed significant delay of recovery from ataxia. A direct intracerebellar injection of IL-1beta-induced ataxia and intracerebellar coinjection of IL-18 counteracted the effect of IL-1beta. Our data firstly show that IL-18 and IL-1beta display differential direct regulation in kainate-induced ataxia in mice. Our results might contribute toward the development of a new therapeutic strategy for cerebellar ataxia in humans.     

CD11b+/Gr-1+ immature myeloid cells mediate suppression of T cells in mice bearing tumors of IL-1beta-secreting cells

Tumor cells secreting IL-1beta are invasive and metastatic, more than the parental line or control mock-transfected cells, and concomitantly induce in mice general immune suppression of T cell responses. Suppression strongly correlates with accumulation in the peripheral blood and spleen of CD11b+/Gr-1+ immature myeloid cells and hematological alterations, such as splenomegaly, leukocytosis, and anemia. Resection of large tumors of IL-1beta-secreting cells restored immune reactivity and hematological alterations within 7-10 days. Treatment of tumor-bearing mice with the physiological inhibitor of IL-1, the IL-1R antagonist, reduced tumor growth and attenuated the hematological alterations. Depletion of CD11b+/Gr-1+ immature myeloid cells from splenocytes of tumor-bearing mice abrogated suppression. Despite tumor-mediated suppression, resection of large tumors of IL-1beta-secreting cells, followed by a challenge with the wild-type parental cells, induced resistance in mice; protection was not observed in mice bearing tumors of mock-transfected fibrosarcoma cells. Altogether, we show in this study that tumor-derived IL-1beta, in addition to its proinflammatory effects on tumor invasiveness, induces in the host hematological alterations and tumor-mediated suppression. Furthermore, the antitumor effectiveness of the IL-1R antagonist was also shown to encompass restoration of hematological alterations, in addition to its favorable effects on tumor invasiveness and angiogenesis that have previously been described by us.