Blood monocytes consist of two principal subsets with distinct migratory properties

Peripheral blood monocytes are a heterogeneous population of circulating leukocytes. Using a murine adoptive transfer system to probe monocyte homing and differentiation in vivo, we identified two functional subsets among murine blood monocytes: a short-lived CX(3)CR1(lo)CCR2(+)Gr1(+) subset that is actively recruited to inflamed tissues and a CX(3)CR1(hi)CCR2(-)Gr1(-) subset characterized by CX(3)CR1-dependent recruitment to noninflamed tissues. Both subsets have the potential to differentiate into dendritic cells in vivo. The level of CX(3)CR1 expression also defines the two major human monocyte subsets, the CD14(+)CD16(-) and CD14(lo)CD16(+) monocytes, which share phenotype and homing potential with the mouse subsets. These findings raise the potential for novel therapeutic strategies in inflammatory diseases.     

抗VEGFR2/抗CD3双特异单链抗体的表达及初步活性检测

目的:构建和表达抗血管内皮细胞生长因子受体2(VEGFR2)/抗CD3双特异单链抗体(bscVEGFR2×CD3),及亲和活性测定。方法:设计抗VEGFR2/抗CD3双特异单链抗体基因序列,由公司合成并亚克隆入真核表达载体pcDNA3.1(+)中,脂质体法转染中国仓鼠卵巢细胞(CHO),筛选高效分泌表达bscVEGFR2×CD3的克隆株。表达产物经Ni-NTA柱纯化,120 g/L SDS-PAGE电泳及Western blot鉴定。应用流式细胞术(FCM)检测生物学活性。结果:bscVEGFR2×CD3重组表达载体测序证实序列正确。bscVEGFR2×CD3能够在CHO细胞中进行分泌表达,筛选出6株高表达克隆株。120 g/L SDS-PAGE显示相对分子质量(Mr)约56 000有1条带,与预期相符,Western blot证明anti-His抗体能与这条蛋白条带发生特异性结合。FCM检测bscVEGFR2×CD3能与CD3+jurkat细胞和VEGFR2+A375细胞特异性结合。结论:成功构建和表达抗VEGFR2/抗CD3双特异单链抗体,该抗体具有与VEGFR2、CD3特异性结合的免疫学活性。     

A bispecific single-chain antibody fusion protein for targeted depletion of autoreactive B cells via unstimulated human T lymphocytes

Autoantigen-specific B cells are culprits in the pathogenesis of many autoimmune diseases either through the production of autoreactive antibodies or as very effective antigen-presenting cells. A general depletion of B cells by a CD20-specific monoclonal IgG1 antibody has recently been validated as an effective strategy for treating rheumatoid arthritis. However, general elimination of B cells can lead to immunosuppression and increased risk of infection. In search for a more specific approach, we have generated a fusion protein for the antigen-specific targeting of autoreactive B cells for re-directed lysis by resting human T lymphocytes. We describe the design, purification and characterization of MOGxanti-CD3, a single-chain bispecific antibody fusion protein recognizing B cell receptors specific for the human myelin oligodendrocyte glycoprotein (MOG) and to CD3 on human T cells. MOGxAnti-CD3 induced selective and very efficient redirected lysis of MOG-reactive B cells through freshly isolated, unstimulated human T cells. Fusions between autoantigens and an anti-CD3 single-chain antibody may be suitable to develop very specific therapeutic approaches for the selective depletion of autoreactive B cells in autoimmune diseases.     

Involvement of CCL25 (TECK) in the generation of the murine small-intestinal CD8alpha alpha+CD3+ intraepithelial lymphocyte compartment

The CC chemokine CCL25 (TECK) is selectively expressed in the thymus and small intestine, indicating a potential role in T lymphocyte development. In the present study we examined the role of CCL25 in the generation of the small-intestinal CD8alpha alpha(+)CD3(+) intraepithelial lymphocyte (IEL) compartment. CCL25 mRNA expression in the murine small intestine increased at three weeks of age and corresponded with the appearance of CD8alpha alpha(+)CD3(+) lymphocytes in the small-intestinal epithelium. Administration of monoclonal neutralizing anti-CCL25 antibody to two-week-old mice led to a approximately 50% reduction in the total number of CD8alpha alpha(+)TCRgamma delta(+) and CD8alpha alpha(+)TCRalpha beta(+) IEL at four weeks of age. Freshly isolated murine CD8alpha alpha(+)CD3(+) IEL migrated in response to CCL25 and expressed the CCL25 receptor, CCR9. Analysis of CCR9 expression on putative IEL precursor populations demonstrated the presence of both CCR9(-) and CCR9(+) cells and indicated that up-regulation of this receptor occurred during IEL precursor differentiation. Finally, data from wild-type and RAG(-/-) mice suggested that the reduction in CD8alpha alpha(+)CD3(+) IEL in anti-CCL25 antibody treated mice resulted primarily from defective maintenance and/or development of IEL precursors rather than a direct effect on mature CD8alpha alpha(+)CD3(+) IEL.     

CCR3-blocking antibody inhibits allergen-induced eosinophil recruitment in human skin xenografts from allergic patients

Eosinophil, basophil, and T helper 2 (TH2) cell recruitment into tissues is a characteristic feature of allergic diseases. These cells have in common the expression of the chemokine receptor CCR3, which may represent a specific pathway for their accumulation in vivo. Although animal models of allergic reactions are available, findings cannot always be extrapolated to man. To overcome these limitations, we have developed a humanized mouse model of allergic cutaneous reaction using severe combined immunodeficiency mice engrafted with skin and autologous peripheral blood mononuclear cells from allergic donors. Intradermal injection of the relevant allergen into human skin xenografts from allergic individuals induced a significant recruitment of human CD4(+) T cells, basophils, and TH2-type cytokine mRNA-expressing cells, as well as murine eosinophils. Human skin xenografts, atopic status, and autologous peripheral blood mononuclear cell reconstitution were all mandatory to induce the allergic reaction. Next, we addressed the role of CCR3 in the endogenous mechanisms involved in the inflammatory cell recruitment in this experimental model of allergic cutaneous reaction. In vivo administration of an anti-human CCR3-blocking antibody selectively reduced accumulation of eosinophils but not that of CD4(+) cells, basophils, or cells expressing mRNA for TH2-type cytokines. These findings establish a new in vivo model of humanized allergic reaction and suggest that eosinophil migration is mediated mainly through CCR3. Finally, these results suggest that this model might be useful to test human-specific antiallergic modulators.     

Renal dendritic cells adopt a pro-inflammatory phenotype in obstructive uropathy to activate T cells but do not directly contribute to fibrosis

Unilateral ureteral obstruction (UUO) is a well-characterized murine model of renal inflammation leading to fibrosis. Renal dendritic cells (DCs) constitute a significant portion of kidney leukocytes and may participate in local inflammation and have critical roles in antigen presentation. The heterogeneity in renal DC populations and surface marker overlap with monocytes/macrophages has made studying renal DCs difficult. These studies used CD11c-promoter driven reporter/depletion mice to study DCs in vivo. Studying early local inflammatory events (day 3 of UUO), in vivo multiphoton imaging of the intact kidney of CD11c reporter mice revealed more dendrite extensions and increased activity of renal DCs in real time. Phenotypic analysis suggested resident DC maturation in obstructed kidneys with increased CD11b and less F4/80 expressed. CD11b(hi) Gr-1(+) inflammatory DCs were also present in obstructed kidneys. T-cell receptor transgenic mice revealed enhanced antigen-presenting capacity of renal DCs after UUO, with increased antigen-specific T-cell proliferation in vivo and ex vivo. However, conditional DC ablation at days 0, 2, or 4 did not attenuate fibrosis or apoptosis 7 days after UUO, and depletion at 7 days did not alter outcomes at day 14. Therefore, after UUO, renal DCs exhibit inflammatory morphological and functional characteristics and are more effective antigen-presenting cells, but they do not directly contribute to tubulointerstitial damage and fibrosis.     

Glucocorticoids induce an activated, anti-inflammatory monocyte subset in mice that resembles myeloid-derived suppressor cells

Glucocorticoids (GC) are still the most widely used immunosuppressive agents in clinical medicine. Surprisingly, little is known about the mechanisms of GC action on monocytes, although these cells exert pro- and anti-inflammatory effects. We have shown recently that GC induce a specific monocyte phenotype with anti-inflammatory properties in humans. We now investigated whether this also applies for the murine system and how this subset would relate to recently defined murine subtypes. After treatment with dexamethasone for 48 h, monocytes up-regulated scavenger receptor CD163 and Gr-1, down-regulated CX(3)CR1, and shared with human GC-treated monocytes functional features such as low adhesiveness but high migratory capacity. They specifically up-regulated anti-inflammatory IL-10, but not TGF-beta, and in contrast to their human counterparts, they down-regulated IL-6. Although GC-induced monocytes down-regulated CX(3)CR1, a distinctive marker for classical/proinflammatory human and murine monocytes (CX(3)CR1(lo)CCR2(+)Ly6C(hi)), they differed from this physiologically occurring subset, as they remained Ly6C(med) and unactivated (CD62 ligand(++)). In addition to their immunosuppressive effects, they were CD11b(+)Gr-1(+) and expressed the IL-4Ralpha chain (CD124), a recently described, signature molecule of tumor-induced myeloid-derived suppressor cells (MDSC). We therefore generated murine MDSC in B16 melanoma-bearing mice and indeed found parallel up-regulation of CD11b(+)Gr-1(+) and CD124 on GC-induced monocytes and MDSC. These data allow us to speculate that the GC-induced subtype shares with inflammatory monocytes the ability to migrate quickly into inflamed tissue, where they, however, exert anti-inflammatory effects and that similarities between GC-induced monocytes and MDSC may be involved in progression of some tumors observed in patients chronically treated with GC.     

MT110: a novel bispecific single-chain antibody construct with high efficacy in eradicating established tumors

We have developed a novel single-chain Ep-CAM-/CD3-bispecific single-chain antibody construct designated MT110. MT110 redirected unstimulated human peripheral T cells to induce the specific lysis of every Ep-CAM-expressing tumor cell line tested. MT110 induced a costimulation independent polyclonal activation of CD4- and CD8-positive T cells as seen by de novo expression of CD69 and CD25, and secretion of interferon gamma, tumor necrosis factor alpha, and interleukins 2, 4 and 10. CD8-positive T cells made the major contribution to redirected tumor cell lysis by MT110. With a delay, CD4-positive cells could also contribute presumably as consequence of a dramatic upregulation of granzyme B expression. MT110 was highly efficacious in a NOD/SCID mouse model with subcutaneously growing SW480 human colon cancer cells. Five daily doses of 1 microg MT110 on days 0-4 completely prevented tumor outgrowth in all mice treated. The bispecific antibody construct also led to a durable eradication of established tumors in all mice treated with 1 microg doses of MT110 on days 8-12 after tumor inoculation. Finally, MT110 could eradicate patient-derived metastatic ovarian cancer tissue growing under the skin of NOD/SCID mice. MT110 appears as an attractive bispecific antibody candidate for treatment of human Ep-CAM-overexpressing carcinomas.     

Tumor-infiltrating myeloid-derived suppressor cells are pleiotropic-inflamed monocytes/macrophages that bear M1- and M2-type characteristics

Here, tumor-infiltrating CD11b(+) myelomonocytoid cells in murine colon adenocarcinoma-38 and GL261 murine glioma were phenotypically characterized. Over 90% were of the CD11b(+)F4/80(+) monocyte/macrophage lineage. They also had a myeloid-derived suppressor cell (MDSC) phenotype, as they suppressed the proliferation of activated splenic CD8(+) T cells and had a CD11b(+)CD11c(+)Gr-1(low)IL-4Ralpha(+) phenotype. In addition, the cells expressed CX(3)CR1 and CCR2 simultaneously, which are the markers of an inflammatory monocyte. The MDSCs expressed CD206, CXCL10, IL-1beta, and TNF-alpha mRNAs. They also simultaneously expressed CXCL10 and CD206 proteins, which are typical, classical (M1) and alternative (M2) macrophage activation markers, respectively. Peritoneal exudate cells (PECs) strongly expressed CD36, CD206, and TGF-beta mRNA, which is characteristic of deactivated monocytes. The MDSCs also secreted TGF-beta, and in vitro culture of MDSCs and PECs with anti-TGF-beta antibody recovered their ability to secrete NO. However, as a result of secretion of proinflammatory cytokines, MDSCs could not be categorized into deactivated monocyte/macrophages. Thus, tumor-infiltrating MDSCs bear pleiotropic characteristics of M1 and M2 monocytes/macrophages. Furthermore, CD206 expression by tumor-infiltrating MDSCs appears to be regulated by an autocrine mechanism that involves TGF-beta.     

Gr1(+) inflammatory monocytes are required for mucosal resistance to the pathogen Toxoplasma gondii

The enteric pathogen Toxoplasma gondii is controlled by a vigorous innate T helper 1 (Th1) cell response in the murine model. We demonstrated that after oral infection, the parasite rapidly recruited inflammatory monocytes [Gr1(+) (Ly6C(+), Ly6G(-)) F4/80(+)CD11b(+)CD11c(-)], which established a vital defensive perimeter within the villi of the ileum in the small intestine. Mice deficient of the chemokine receptor CCR2 or the ligand CCL2 failed to recruit Gr1(+) inflammatory monocytes, whereas dendritic cells and resident tissue macrophages remained unaltered. The selective lack of Gr1(+) inflammatory monocytes resulted in an inability of mice to control replication of the parasite, high influx of neutrophils, extensive intestinal necrosis, and rapid death. Adoptive transfer of sorted Gr1(+) inflammatory monocytes demonstrated their ability to home to the ileum in infected animals and protect Ccr2(-/-) mice, which were otherwise highly susceptible to oral toxoplasmosis. Collectively, these findings illustrate the critical importance of inflammatory monocytes as a first line of defense in controlling intestinal pathogens.     

CD11b+ bone marrow-derived monocytes are the major leukocyte subset responsible for retinal capillary leukostasis in experimental diabetes in mouse and express high levels of CCR5 in the circulation

We investigated the phenotype of cells involved in leukostasis in the early stages of streptozotocin-induced diabetes in mice by direct observation and by adoptive transfer of calcein-AM-labeled bone marrow-derived leukocytes from syngeneic mice. Retinal whole mounts, confocal microscopy, and flow cytometry ex vivo and scanning laser ophthalmoscopy in vivo were used. Leukostasis in vivo and ex vivo in retinal capillaries was increased after 2 weeks of diabetes (Hb A(1c), 14.2 ± 1.2) when either donor or recipient mice were diabetic. Maximum leukostasis occurred when both donor and recipient were diabetic. CD11b(+), but not Gr1(+), cells were preferentially entrapped in retinal vessels (fivefold increase compared with nondiabetic mice). In diabetic mice, circulating CD11b(+) cells expressed high levels of CCR5 (P = 0.04), whereas spleen (P = 0.0001) and retinal (P = 0.05) cells expressed increased levels of the fractalkine chemokine receptor. Rosuvastatin treatment prevented leukostasis when both recipient and donor were treated but not when donor mice only were treated. This effect was blocked by treatment with mevalonate. We conclude that leukostasis in early diabetic retinopathy involves activated CCR5(+)CD11b(+) myeloid cells (presumed monocytes). However, leukostasis also requires diabetes-induced changes in the endothelium, because statin therapy prevented leukostasis only when recipient mice were treated. The up-regulation of the HMG-CoA reductase pathway in the endothelium is the major metabolic dysregulation promoting leukostasis.     

CCR9+ T cells contribute to the resolution of the inflammatory response in a mouse model of intestinal amoebiasis

Analysis of the mechanisms underlying the inflammatory response in amoebiasis is important to understand the immunopathology of the disease. Mucosal associated effector and regulatory T cells may play a role in regulating the inflammatory immune response associated to Entamoeba histolytica infection in the colon. A subpopulation of regulatory T cells has recently been identified and is characterized by the expression of the chemokine receptor CCR9. In this report, we used CCR9 deficient (CCR9(-/-)) mice to investigate the role of the CCR9(+) T cells in a murine model of E. histolytica intestinal infection. Intracecal infection of CCR9(+/+), CCR9(+/-) and CCR9(-/-) mice with E. histolytica trophozoites, revealed striking differences in the development and nature of the intestinal inflammatory response observed between these strains. While CCR9(+/+) and CCR9(+/-) mice were resistant to the infection and resolved the pathogen-induced inflammatory response, CCR9(-/-) mice developed a chronic inflammatory response, which was associated with over-expression of the cytokines IFN-γ, TNF-α, IL-4, IL-6 and IL-17, while IL-10 was not present. In addition, increased levels of CCL11, CCL20 and CCL28 chemokines were detected by qRT-PCR in CCR9(-/-) mice. E. histolytica trophozoites were identified in the lumen of the cecum of CCR9(-/-) mice at seven days post infection (pi), whereas in CCR9(+/+) mice trophozoites disappeared by day 1 pi. Interestingly, the inflammation observed in CCR9(-/-) mice, was associated with a delayed recruitment of CD4(+)CD25(+)FoxP3(+) T cells to the cecal epithelium and lamina propria, suggesting that this population may play a role in the early regulation of the inflammatory response against E. histolytica, likely through IL-10 production. In support of these data, CCR9(+) T cells were also identified in colon tissue sections obtained from patients with amoebic colitis. Our data suggest that a population of CCR9(+)CD4(+)CD25(+)FoxP3(+) T cells may participate in the control and resolution of the inflammatory immune response to E. histolytica infection.     

Compartment-specific remodeling of splenic micro-architecture during experimental visceral leishmaniasis

Progressive splenomegaly is a hallmark of visceral leishmaniasis in humans, canids, and rodents. In experimental murine visceral leishmaniasis, splenomegaly is accompanied by pronounced changes in microarchitecture, including expansion of the red pulp vascular system, neovascularization of the white pulp, and remodeling of the stromal cell populations that define the B-cell and T-cell compartments. Here, we show that Ly6C/G(+) (Gr-1(+)) cells, including neutrophils and inflammatory monocytes, accumulate in the splenic red pulp during infection. Cell depletion using monoclonal antibody against either Ly6C/G(+) (Gr-1; RB6) or Ly6G(+) (1A8) cells increased parasite burden. In contrast, depletion of Ly6C/G(+) cells, but not Ly6G(+) cells, halted the progressive remodeling of Meca-32(+) and CD31(+) red pulp vasculature. Strikingly, neither treatment affected white pulp neovascularization or the remodeling of the fibroblastic reticular cell and follicular dendritic cell networks. These findings demonstrate a previously unrecognized compartment-dependent selectivity to the process of splenic vascular remodeling during experimental murine visceral leishmaniasis, attributable to Ly6C(+) inflammatory monocytes.     

Fcγ receptor-dependent effector mechanisms regulate CD19 and CD20 antibody immunotherapies for B lymphocyte malignancies and autoimmunity

Immunotherapy using Rituximab, an unconjugated CD20 monoclonal antibody, has proven effective for treating non-Hodgkin’s lymphoma and autoimmune disease. CD19 antibody immunotherapy is also effective in mouse models of lymphoma and autoimmunity. In both cases, mouse models have demonstrated that effector cell networks effectively deplete the vast majority of circulating and tissue B lymphocytes through Fcγ receptor-dependent pathways. In mice, B cell depletion is predominantly, if not exclusively, mediated by monocytes. CD20 mAbs rapidly deplete circulating and tissue B cells in an antibody isotype-restricted manner with a hierarchy of antibody effectiveness: IgG2a/c?>?IgG1?>?IgG2b?>>?IgG3. Depending on antibody isotype, mouse B cell depletion is regulated by FcγRI-, FcγRII-, FcγRIII-, and FcγRIV-dependent pathways. The potency of IgG2a/c mAbs for B cell depletion in vivo results from FcγRIV interactions, with likely contributions from high-affinity FcγRI. IgG1 mAbs induce B cell depletion through preferential, if not exclusive, interactions with low-affinity FcγRIII, while IgG2b mAbs interact preferentially with intermediate-affinity FcγRIV. By contrast, inhibitory FcγRIIB-deficiency significantly increases CD20 mAb-induced B cell depletion at low mAb doses by enhancing monocyte function. Thus, isotype-specific mAb interactions with distinct FcγRs contribute significantly to the effectiveness of CD20 mAbs in vivo. These results provide a molecular basis for earlier observations that human FcγRII and FcγRIII polymorphisms correlate with the in vivo effectiveness of CD20 antibody therapy. That the innate monocyte network depletes B cells through FcγR-dependent pathways during immunotherapy has important clinical implications for CD19, CD20, and other antibody-based therapies for the treatment of diverse B cell malignancies and autoimmune disease.     

Depletion of inflammatory dendritic cells with anti-CD209 conjugated to saporin toxin

Monocytes rapidly infiltrate inflamed tissues and differentiate into CD209⁺ inflammatory dendritic cells (DCs) that promote robust immunity or, if unregulated, inflammatory disease. Previous studies in experimental animal models indicate that inflammatory DC depletion through systemic elimination of their monocyte precursors with clodronate-loaded liposomes ameliorates the development of psoriasis and other diseases. However, translation of systemic monocyte depletion strategies is difficult due to the importance of monocytes during homeostasis and infection clearance. Here, we describe a strategy that avoids the monocyte intermediates to deplete inflammatory DCs through antibody-loaded toxin. Mice with an abundance of inflammatory DCs as a consequence of lipopolysaccharide exposure were treated with anti-CD209 antibody conjugated to saporin, a potent ribosome inactivator. The results demonstrate depletion of CD209⁺ DCs. This strategy could prove useful for the targeted reduction of inflammatory DCs in disease.     

Neutrophils sustain pathogenic CD8+ T cell responses in the heart

This study explores the influence of innate immunity on CD8(+) T-cell responses against heart tissue. Adoptive transfer of ovalbumin-specific CD8(+) effector T cells into CMy-mOva mice, which express ovalbumin in cardiac myocytes, results in a lethal acute myocarditis. The inflammatory infiltrate in the heart includes neutrophils as well as T cells. We used anti-Ly6G antibody to transiently deplete neutrophils at the time of onset of disease. By day 7 after receiving 5 x 10(5) CD8(+) effector T cells, 100% of control Ig-treated CMy-mOva mice had died, while 85% of anti-Ly6G-treated mice survived indefinitely. CD8(+) T-cell infiltration and tissue damage were present in both groups, but the disease was limited in the anti-Ly6G-treated mice, with a rapid disappearance of the adoptively transferred CD8(+) T cells within 11 days. Recovery occurred even though blood neutrophil counts began to rise 48 hours after the last anti-Ly6G treatment. Recovery was associated with a chronic CD4(+) cell infiltrate, and a rapid decline in expression of IFN-gamma and IP-10 mRNA in the myocardium. Neutrophil depletion did not effect survival of CMy-mOva mice that received 3 x 10(6) CD8(+) T cells. These data show that granulocytic inflammation sustains CD8(+) T-cell-mediated heart disease, which has important implications for the pathogenesis and treatment of acute myocarditis and allograft rejection.     

Allergen-induced CD11b+ CD11c(int) CCR3+ macrophages in the lung promote eosinophilic airway inflammation in a mouse asthma model

Although the recruitment of macrophages to the lung is a central feature of airway inflammation, its function in ongoing T(h)2 cell-mediated eosinophilic airway inflammation remains controversial. Here, we have demonstrated that the allergen-induced CD11b(+) CD11c(int) macrophage expressing CC chemokine receptor 3 (CCR3) in the lung performs a crucial function in the induction of eosinophilic asthma in a murine model. In the lungs of normal mice, residential cells evidencing high granularity phenotypically evidenced CD11b(int) CD11c(+) or CD11b(+) CD11c(int) cells, appearing at a 2:1 ratio. After allergen challenge, however, this reverses dramatically, up to a ratio of one to six. Approximately 91% of increased CD11b(+) CD11c(int) cells evidenced the expression of the CCR3 eotaxin receptor, but not other chemokine receptors, such as CCR5 and CXCR4. Interestingly, the CD11b(+) CD11c(int) cells purified from the lungs of OVA (ovalbumin)-sensitized and challenged mice evidenced higher antigen-presenting activity than was observed in CD11b(int) CD11c(+) cells. In order to investigate the in vivo function of CD11b(+) CD11c(int) cells, the cells were isolated from the lungs of OVA-sensitized and challenged mice and then adoptively transferred prior to the allergen challenge of normal mice. In the CD11b(+) CD11c(int)-transferred mice airway hyperresponsiveness, eosinophilic inflammation in the lung and T(h)2 cytokine secretion in the bronchoalveolar lavage fluids were significantly enhanced as the result of OVA challenge, as compared with the mice that received OVA-primed CD90(+) T cells or CD11b(int) CD11c(+) cells. These findings show that CD11b(+) CD11c(int) macrophages expressing CCR3 as key pro-inflammatory cells are both necessary and sufficient for allergen-specific T cell stimulation during ongoing eosinophilic airway inflammation.     

Immunomodulatory effects of anti-CD4 antibody in host resistance against infections and tumors in human CD4 transgenic mice

Anti-CD4 antibodies, which cause CD4(+) T-cell depletion, have been shown to increase susceptibility to infections in mice. Thus, development of anti-CD4 antibodies for clinical use raises potential concerns about suppression of host defense mechanisms against pathogens and tumors. The anti-human CD4 antibody keliximab, which binds only human and chimpanzee CD4, has been evaluated in host defense models using murine CD4 knockout-human CD4 transgenic (HuCD4/Tg) mice. In these mice, depletion of CD4(+) T cells by keliximab was associated with inhibition of anti-Pneumocystis carinii and anti-Candida albicans antibody responses and rendered HuCD4/Tg mice susceptible to P. carinii, a CD4-dependent pathogen, but did not compromise host defense against C. albicans infection. Treatment of HuCD4/Tg mice with corticosteroids impaired host immune responses and decreased survival for both infections. Resistance to experimental B16 melanoma metastases was not affected by treatment with keliximab, in contrast to an increase in tumor colonization caused by anti-T cell Thy1.2 and anti-asialo GM-1 antibodies. These data suggest an immunomodulatory rather than an overt immunosuppressive activity of keliximab. This was further demonstrated by the differential effect of keliximab on type 1 and type 2 cytokine expression in splenocytes stimulated ex vivo. Keliximab caused an initial up-regulation of interleukin-2 (IL-2) and gamma interferon, followed by transient down-regulation of IL-4 and IL-10. Taken together, the effects of keliximab in HuCD4/Tg mice suggest that in addition to depleting circulating CD4(+) T lymphocytes, keliximab has the capability of modulating the function of the remaining cells without causing general immunosuppression. Therefore, keliximab therapy may be beneficial in controlling certain autoimmune diseases.