IL-2 receptor blockade inhibits late, but not early, IFN-gamma and CD40 ligand expression in human T cells: disruption of both IL-12-dependent and -independent pathways of IFN-gamma production

An immunomodulating peptide to counteract solar radiation-induced immunosuppression and DNA damage

Ultraviolet radiation (UVR) induces immunosuppression and DNA damage, both of which contribute to the rising global incidence of skin cancer including melanoma. Nucleotide excision repair, which is activated upon UVR-induced DNA damage, is linked to expression of interleukin-12 (IL-12) which serves to limit immunosuppression and augment the DNA repair process. Herein, we report an immunomodulating peptide, designated IK14800, that not only elicits secretion of IL-12, interleukin-2 (IL-2) and interferon-gamma (IFN-γ) but also reduces DNA damage in the skin following exposure to UVR. Combined with re-invigoration of exhausted CD4+ T cells, inhibition of UVR-induced MMP-1 release and suppression of B16F10 melanoma metastases, IK14800 offers an opportunity to gain further insight into mechanisms underlying the development and progression of skin cancers.

A novel lipidic peptide with potential to promote balanced effector-regulatory T cell responses

T cell-dendritic cell (DC) interactions contribute to reciprocal stimulation leading to DC maturation that results in production of interleukin-12 (IL-12) and interferon-gamma (IFN-γ). Both cytokines have been implicated in autoimmune diseases while being necessary for effective immune responses against foreign antigens. We describe a lipidic peptide, designated IK14004, that modifies crosstalk between T cells and DCs resulting in suppression of IL-12p40/IFN-γ production. T cell production of interleukin-2 (IL-2) and IFN-γ is uncoupled and IL-12p70 production is enhanced. IK14004 induces expression of activating co-receptors in CD8+ T cells and increases the proportion of Foxp3-expressing CD4+ T regulatory cells. The potential for IK14004 to impact on signalling pathways required to achieve a balanced immune response upon stimulation of DCs and T cells is highlighted. This novel compound provides an opportunity to gain further insights into the complexity of T cell-DC interactions relevant to autoimmunity associated with malignancies and may have therapeutic benefit.

Pre-Clinical Autoimmunity in Lupus Relatives: Self-Reported Questionnaires and Immune Dysregulation Distinguish Relatives Who Develop Incomplete or Classified Lupus From Clinically Unaffected Relatives and Unaffected, Unrelated Individuals

Systemic lupus erythematosus (SLE) is propelled by pathogenic autoantibody (AutoAb) and immune pathway dysregulation. Identifying populations at risk of reaching classified SLE is essential to curtail inflammatory damage. Lupus blood relatives (Rel) have an increased risk of developing SLE. We tested factors to identify Rel at risk of developing incomplete lupus (ILE) or classified SLE vs. clinically unaffected Rel and healthy controls (HC), drawing from two unique, well characterized lupus cohorts, the lupus autoimmunity in relatives (LAUREL) follow-up cohort, consisting of Rel meeting <4 ACR criteria at baseline, and the Lupus Family Registry and Repository (LFRR), made up of SLE patients, lupus Rel, and HC. Medical record review determined ACR SLE classification criteria; study participants completed the SLE portion of the connective tissue disease questionnaire (SLE-CSQ), type 2 symptom questions, and provided samples for assessment of serum SLE-associated AutoAb specificities and 52 plasma immune mediators. Elevated SLE-CSQ scores were associated with type 2 symptoms, ACR scores, and serology in both cohorts. Fatigue at BL was associated with transition to classified SLE in the LAUREL cohort (p≤0.01). Increased levels of BLyS and decreased levels of IL-10 were associated with type 2 symptoms (p<0.05). SLE-CSQ scores, ACR scores, and accumulated AutoAb specificities correlated with levels of multiple inflammatory immune mediators (p<0.05), including BLyS, IL-2Rα, stem cell factor (SCF), soluble TNF receptors, and Th-1 type mediators and chemokines. Transition to SLE was associated with increased levels of SCF (p<0.05). ILE Rel also had increased levels of TNF-α and IFN-γ, offset by increased levels of regulatory IL-10 and TGF-β (p<0.05). Clinically unaffected Rel (vs. HC) had higher SLE-CSQ scores (p<0.001), increased serology (p<0.05), and increased inflammatory mediator levels, offset by increased IL-10 and TGF-β (p<0.01). These findings suggest that Rel at highest risk of transitioning to classified SLE have increased inflammation coupled with decreased regulatory mediators. In contrast, clinically unaffected Rel and Rel with ILE demonstrate increased inflammation offset with increased immune regulation, intimating a window of opportunity for early intervention and enrollment in prevention trials.

Targeting the CD40-CD40L pathway in autoimmune diseases: Humoral immunity and beyond

CD40 is a TNF receptor superfamily member expressed on both immune and non-immune cells. Interactions between B cell-expressed CD40 and its binding partner, CD40L, predominantly expressed on activated CD4+ T cells, play a critical role in promoting germinal center formation and the production of class-switched antibodies. Non-hematopoietic cells expressing CD40 can also engage CD40L and trigger a pro-inflammatory response. This article will highlight what is known about the biology of the CD40-CD40L axis in humans and describe the potential contribution of CD40 signaling on both hematopoietic and non-hematopoietic cells to autoimmune disease pathogenesis. Additionally, novel therapeutic approaches to target this pathway, currently being evaluated in clinical trials, are discussed.

Modeling Cell-to-Cell Communication Networks Using Response-Time Distributions

Cell-to-cell communication networks have critical roles in coordinating diverse organismal processes, such as tissue development or immune cell response. However, compared with intracellular signal transduction networks, the function and engineering principles of cell-to-cell communication networks are far less understood. Major complications include: cells are themselves regulated by complex intracellular signaling networks; individual cells are heterogeneous; and output of any one cell can recursively become an additional input signal to other cells. Here, we make use of a framework that treats intracellular signal transduction networks as "black boxes" with characterized input-to-output response relationships. We study simple cell-to-cell communication circuit motifs and find conditions that generate bimodal responses in time, as well as mechanisms for independently controlling synchronization and delay of cell-population responses. We apply our modeling approach to explain otherwise puzzling data on cytokine secretion onset times in T cells. Our approach can be used to predict communication network structure using experimentally accessible input-to-output measurements and without detailed knowledge of intermediate steps.

T helper type 1-related molecules as well as interleukin-15 are hyperexpressed in the skin lesions of patients with pyoderma gangrenosum

Pyoderma gangrenosum (PG) is a rare, immune-mediated skin disease classified into the group of neutrophilic dermatoses. Although a number of studies confirmed the central role of innate immunity, only few studies have investigated the possible contributing role of acquired immunity. In particular, no reports concerning T helper type 1 (Th1) and Th2 cells are available as yet. Therefore, 15 patients with PG, five with Sweet's syndrome (SS) and nine skin specimens from healthy controls (HC) were investigated, evaluating the expression of Th1-related markers interleukin (IL)-12, interferon (IFN)-γ, C-X-C motif chemokine receptor 3 (CXCR3) and C-C motif chemokine receptor 5 (CCR5), of the Th2-related molecules IL-4, IL-5, IL-13 and CCR3, of the co-stimulatory axis CD40/CD40 ligand, of IL-15 and the natural killer (NK) cell marker CD56 in skin lesions by immunohistochemistry. Patients with PG and SS showed a higher expression of Th1 markers than HC. Conversely, IL-5- and CCR3-expressing cells were less numerous in PG skin lesions compared to SS (P = 0·0157 and < 0·0001, respectively). Both CD40 and CD40L were expressed more in PG than in SS and HC (P < 0·0001 for both). Finally, the number of IL-15⁺ and CD56⁺ cells was higher in the skin of patients with PG than in those of SS and HC (P < 0·0001 for both). Our results suggest that Th2 cells are down-regulated in PG. At the same time, over-expression of the co-stimulatory axis CD40/CD40L amplifies the impairment of the Th1/Th2 balance. Both these findings might explain the most aggressive behaviour of PG in comparison to SS. Moreover, over-expression of IL-15⁺ and CD56⁺ cells may suggest a possible role of NK cells in the pathogenesis of the disease.

Spotlight on daclizumab: its potential in the treatment of multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory-demyelinating disease of the central nervous system of a putative autoimmune etiology. Although the exact pathogenic mechanisms underlying demyelination and axonal damage in MS are not fully understood, T-cells are believed to play a central role in the pathogenesis of the disease. Daclizumab is a humanized binding monoclonal antibody that binds to the Tac epitope on the α-subunit (CD25) of the interleukin-2 (IL-2) receptor, thus effectively blocking the formation of the high-affinity IL-2 receptor, which is expressed mainly on T-cells. A series of clinical trials in patients with relapsing MS demonstrated a profound effect of daclizumab on inflammatory disease activity and improved clinical outcomes compared with placebo or interferon-β, which led to the recent approval of daclizumab (Zinbryta™) for the treatment of relapsing forms of MS. Enhancement of endogenous mechanisms of immune regulation rather than inhibition of effector T-cells might explain the effects of daclizumab in MS. These include expansion and improved function of regulatory CD56bright NK cells, inhibition of the early activation of T-cells through blockade of IL-2 transpresentation by dendritic cells and reduction in the number of intrathecal proinflammatory lymphoid tissue inducer cells. The enhanced efficacy of daclizumab is accompanied by an increased frequency of adverse events and risks of serious adverse events, thus placing it as a second-line therapy and calling for the implementation of a strict risk management program. This review details the mechanisms of action of daclizumab, discusses its efficacy and safety in patients with MS, and provides an insight into the place of this novel therapy in the treatment of MS.

The CD25-binding antibody Daclizumab High-Yield Process has a distinct glycosylation pattern and reduced antibody-dependent cell-mediated cytotoxicity in comparison to Zenapax®

The CD25-binding antibody daclizumab high-yield process (DAC HYP) is an interleukin (IL)-2 signal modulating antibody that shares primary amino acid sequence and CD25 binding affinity with Zenapax®, a distinct form of daclizumab, which was approved for the prevention of acute organ rejection in patients receiving renal transplants as part of an immunosuppressive regimen that includes cyclosporine and corticosteroids. Comparison of the physicochemical properties of the two antibody forms revealed the glycosylation profile of DAC HYP differs from Zenapax in both glycan distribution and the types of oligosaccharides, most notably high-mannose, galactosylated and galactose-α-1,3-galactose (α-Gal) oligosaccharides, resulting in a DAC HYP antibody material that is structurally distinct from Zenapax. Although neither antibody elicited complement-dependent cytotoxicity in vitro, DAC HYP antibody had significantly reduced levels of antibody-dependent cell-mediated cytotoxicity (ADCC). The ADCC activity required natural killer (NK) cells, but not monocytes, suggesting the effects were mediated through binding to Fc-gamma RIII (CD16). Incubation of each antibody with peripheral blood mononuclear cells also caused the down-modulation of CD16 expression on NK cells and the CD16 down-modulation was greater for Zenapax in comparison to that observed for DAC HYP. The substantive glycosylation differences between the two antibody forms and corresponding greater Fc-mediated effector activities by Zenapax, including cell killing activity, manifest as a difference in the biological function and pharmacology between DAC HYP and Zenapax.

The efficacy and safety of daclizumab and its potential role in the treatment of multiple sclerosis

Daclizumab is a humanized monoclonal antibody of the immunoglobulin G1 (IgG1) isotype that binds to the α-subunit (CD25) of the high-affinity interleukin-2 (IL-2) receptor expressed on activated T cells and CD4+CD25+FoxP3+ regulatory T cells. Based on the assumption that it would block the activation and expansion of autoreactive T cells that are central to the immune pathogenesis of multiple sclerosis (MS), daclizumab was tested in several small open-label clinical trials in MS and demonstrated a profound inhibition of inflammatory disease activity. Surprisingly, accompanying mechanistic studies revealed that the most important biological effect of daclizumab was rather a dramatic expansion and activation of immunoregulatory CD56(bright) natural-killer (NK) cells that correlated with treatment response, while there was no or only minor effect on peripheral T-cell activation and function. These CD56(bright) NK cells were able to gain access to the central nervous system in MS and kill autologous activated T cells. Additional and relatively large phase IIb clinical trials showed that daclizumab, as add-on or monotherapy in relapsing-remitting (RR) MS, was highly effective in reducing relapse rate, disability progression, and the number and volume of gadolinium-enhancing, T1 and T2 lesions on brain magnetic resonance imaging (MRI), and reproduced the expansion of CD56(bright) NK cells as a biomarker for daclizumab activity. Daclizumab is generally very well tolerated and has shown a favorable adverse event (AE) profile in transplant recipients. However, several potentially serious and newly emerging AEs (mainly infections, skin reactions, elevated liver function tests and autoimmune phenomena in several body organs) may require strict safety monitoring programs in future clinical practice and place daclizumab together with other new and highly effective MS drugs as a second-line therapy. Ongoing phase III clinical trials in RRMS are expected to provide definite information on the efficacy and safety of daclizumab and to determine its place in the fast-growing armamentarium of MS therapies.

An anti-interleukin-2 receptor drug attenuates T- helper 1 lymphocytes-mediated inflammation in an acute model of endotoxin-induced uveitis

The aim of the present study was to evaluate the anti-inflammatory efficacy of Daclizumab, an anti-interleukin-2 receptor drug, in an experimental uveitis model upon a subcutaneous injection of lipopolysaccharide into Lewis rats, a valuable model for ocular acute inflammatory processes. The integrity of the blood-aqueous barrier was assessed 24 h after endotoxin-induced uveitis by evaluating two parameters: cell count and protein concentration in aqueous humors. The histopathology of all the ocular structures (cornea, lens, sclera, choroid, retina, uvea, and anterior and posterior chambers) was also considered. Enzyme-linked immunosorbent assays of the aqueous humor samples were performed to quantify the levels of the different chemokine and cytokine proteins. Similarly, a biochemical analysis of oxidative stress-related markers was also assessed. The inflammation observed in the anterior chamber of the eyes when Daclizumab was administered with endotoxin was largely prevented since the aqueous humor protein concentration substantially lowered concomitantly with a significant reduction in the uveal and vitreous histopathological grading. Th1 lymphocytes-related cytokines, such as Interleukin-2 and Interferon-γ, also significantly reduced with related anti-oxidant systems recovery. Daclizumab treatment in endotoxin-induced uveitis reduced Th1 lymphocytes-related cytokines, such as Interleukin-2 and Interferon gamma, by about 60–70% and presented a preventive role in endotoxin-induced oxidative stress. This antioxidant protective effect of Daclizumab may be related to several of the observed Daclizumab effects in our study, including IL-6 cytokine regulatory properties and a substantial concomitant drop in INFγ. Concurrently, Daclizumab treatment triggered a significant reduction in both the uveal histopathological grading and protein concentration in aqueous humors, but not in cellular infiltration.

FRA2 is a STAT5 target gene regulated by IL-2 in human CD4 T cells

Signal transducers and activators of transcription 5(STAT5) are cytokine induced signaling proteins, which regulate key immunological processes, such as tolerance induction, maintenance of homeostasis, and CD4 T-effector cell differentiation. In this study, transcriptional targets of STAT5 in CD4 T cells were studied by Chromatin Immunoprecipitation (ChIP). Genomic mapping of the sites cloned and identified in this study revealed the striking observation that the majority of STAT5-binding sites mapped to intergenic (>50 kb upstream) or intronic, rather than promoter proximal regions. Of the 105 STAT5 responsive binding sites identified, 94% contained the canonical (IFN-γ activation site) GAS motifs.

A number of putative target genes identified here are associated with tumor biology. Here, we identified Fos-related antigen 2 (FRA2) as a transcriptional target of IL-2 regulated STAT5. FRA2 is a basic -leucine zipper (bZIP) motif ‘Fos’ family transcription factor that is part of the AP-1 transcription factor complex and is also known to play a critical role in the progression of human tumours and more recently as a determinant of T cell plasticity. The binding site mapped to an internal intron within the FRA2 gene. The epigenetic architecture of FRA2, characterizes a transcriptionally active promoter as indicated by enrichment for histone methylation marks H3K4me1, H3K4me2, H3K4me3, and transcription/elongation associated marks H2BK5me1 and H4K20me1. FRA2 is regulated by IL-2 in activated CD4 T cells. Consistently, STAT5 bound to GAS sequence in the internal intron of FRA2 and reporter gene assays confirmed IL-2 induced STAT5 binding and transcriptional activation. Furthermore, addition of JAK3 inhibitor (R333) or Daclizumab inhibited the induction in TCR stimulated cells. Taken together, our data suggest that FRA2 is a novel STAT5 target gene, regulated by IL-2 in activated CD4 T cells.

Immunological mechanism of action and clinical profile of disease-modifying treatments in multiple sclerosis

Multiple sclerosis (MS) is a life-long, potentially debilitating disease of the central nervous system (CNS). MS is considered to be an immune-mediated disease, and the presence of autoreactive peripheral lymphocytes in CNS compartments is believed to be critical in the process of demyelination and tissue damage in MS. Although MS is not currently a curable disease, several disease-modifying therapies (DMTs) are now available, or are in development. These DMTs are all thought to primarily suppress autoimmune activity within the CNS. Each therapy has its own mechanism of action (MoA) and, as a consequence, each has a different efficacy and safety profile. Neurologists can now select therapies on a more individual, patient-tailored basis, with the aim of maximizing potential for long-term efficacy without interruptions in treatment. The MoA and clinical profile of MS therapies are important considerations when making that choice or when switching therapies due to suboptimal disease response. This article therefore reviews the known and putative immunological MoAs alongside a summary of the clinical profile of therapies approved for relapsing forms of MS, and those in late-stage development, based on published data from pivotal randomized, controlled trials.

Daclizumab, an IL-2 modulating antibody for treatment of multiple sclerosis

Daclizumab is a monoclonal antibody specific for the IL-2R α chain (CD25). Daclizumab has been observed to have multiple mechanisms of action, which may contribute to beneficial effects in immune-related disease and particularly in relapsing and remitting multiple sclerosis (RRMS). These include inhibition of activated immune cells, increase of regulatory natural killer cells, effects on dendritic cells, inhibition of innate lymphoid tissue inducer cells and altered responses involving IL-2 transpresentation. The antibody has shown considerable promise in open-label and early Phase II clinical trials when used as a monotherapy, or in combination with IFN-β. In recently completed randomized trials in RRMS, treatment with daclizumab monotherapy compared with placebo resulted in clinically meaningful and statistically significant reductions in relapses, active lesions on brain MRI and slowing of disability progression. A large Phase III trial in RRMS is ongoing.

Impaired NFAT and NFκB activation are involved in suppression of CD40 ligand expression by Δ(9)-tetrahydrocannabinol in human CD4(+) T cells

We have previously reported that Δ(9)-tetrahydrocannabinol (Δ(9)-THC), the main psychoactive cannabinoid in marijuana, suppresses CD40 ligand (CD40L) expression by activated mouse CD4(+) T cells. CD40L is involved in pathogenesis of many autoimmune and inflammatory diseases. In the present study, we investigated the molecular mechanism of Δ(9)-THC-mediated suppression of CD40L expression using peripheral blood human T cells. Pretreatment with Δ(9)-THC attenuated CD40L expression in human CD4(+) T cells activated by anti-CD3/CD28 at both the protein and mRNA level, as determined by flow cytometry and quantitative real-time PCR, respectively. Electrophoretic mobility shift assays revealed that Δ(9)-THC suppressed the DNA-binding activity of both NFAT and NFκB to their respective response elements within the CD40L promoter. An assessment of the effect of Δ(9)-THC on proximal T cell-receptor (TCR) signaling induced by anti-CD3/CD28 showed significant impairment in the rise of intracellular calcium, but no significant effect on the phosphorylation of ZAP70, PLCγ1/2, Akt, and GSK3β. Collectively, these findings identify perturbation of the calcium-NFAT and NFκB signaling cascade as a key mechanistic event by which Δ(9)-THC suppresses human T cell function.

TH1 cytokine response to HCV peptides in Egyptian health care workers: a pilot study

Our objective was to elucidate the effects of different HCV peptides on TH1 cytokine synthesis (interleukin 2(IL2), gamma interferon (INFγ) and tumor necrosis factor α (TNF α)), in a proliferative response in a high risk population of HCV seronegative aviremic Egyptian healthcare workers (HCW). We studied the TH1 cytokine response to different HCV peptides among 47 HCW with and without evidence of HCV infection. Participants were classified according to the proliferation index (PI) in a CFSE proliferation assay as an indicator of previous exposure to HCV. Cytokines were analyzed using Luminex xMAP technology. Results showed that positive PI HCW produced a higher IL2 in response to all HCV peptides except NS4, a higher IFNγ response to NS3 and NS4 and no difference in TNFα response when compared to the negative PI HCWs. When compared to chronic HCV HCW, positive PI HCW showed no difference in the IL2 response, a higher IFNγ response to NS4 and NS5 HCV peptides and a higher TNFα response to all peptides. In conclusion the magnitude and type of cytokines produced in HCV infection is critical in determining the outcome of infection. NS4 & NS5 HCV peptides induce a protective TH1 response in positive PI HCW.

Effect of activated human polymorphonuclear leucocytes on T lymphocyte proliferation and viability

Human polymorphonuclear leucocytes (PMN) are thought to be immunosuppressive. The suppressive mechanism(s) used by PMN are, however, not well defined and in this study they were analysed using T-cell responses to CD3(+) CD28 monoclonal antibodies (mAb) as a readout. We demonstrate that in vitro activated PMN (PMN(act)) can, without any T-cell interaction, induce apparent T-cell suppression by inhibiting the stimulatory capacity of the CD3 mAb. However, a cell-directed suppression of T-cell proliferation was observed when PMN(act) were added to pre-activated T cells that are already committed to polyclonal proliferation. This suppression was partially reversed by catalase addition (P < 0·01) and largely reversed by addition of exogenous interleukin-2 (P < 0·001) but was not significantly reduced by nitric oxide synthase inhibition, myeloperoxidase inhibition or addition of excess arginine. Following removal of PMN(act) , suppressed T cells could respond normally to further stimulation. In addition to suppressing proliferation, co-culture with PMN(act) also induced a significant decrease in T-cell viability that was reversed by catalase addition (P < 0·05). The addition of the arginase inhibitor N-hydroxy-nor-l-arginine induced both a further significant, catalase-sensitive, loss in T-cell viability and increased nitrite release (P < 0·001). These data demonstrate that PMN, when activated, can both induce T-cell death and reversibly inhibit proliferation of activated T cells. The mechanisms underlying these distinct processes and the effects of arginase inhibitors on PMN induced cytotoxicity merit further investigation.

Lycopene inhibits lymphocyte proliferation through mechanisms dependent on early cell activation

SCOPE

Epidemiological evidence suggests that lycopene is potentially cardio-protective. Recruitment and activation of T cells in the arterial wall is a critical process during atherogenesis, but the effects of lycopene on T-cell response remain to be elucidated. We aimed to determine whether lycopene could modulate T-cell function and activity.

METHODS AND RESULTS

Peripheral blood mononuclear cells from 16 healthy adults were cultured in the presence of lycopene-enriched liposomes (0-2.9 μg lycopene/mL) with or without mitogens. Cell cycle as well as the expression of CD69 (marker of early cell activation), CD25 (IL-2 receptor), and CD11a (late activation marker) were measured in T cells, T-helper cells, and T-cytotoxic cells by flow cytometry. IL-2 secretion and cell proliferation were determined by ELISA and [³H]-thymidine incorporation, respectively. Lycopene significantly inhibited lymphocyte proliferation (up to 40%) in activated cells. Lycopene also significantly inhibited CD69 expression (by up to 12%) as well as IL-2 secretion (by up to 29%). However, CD25 and CD11a expression as well as the cell-cycle profile were unaffected by lycopene.

CONCLUSION

Lycopene influences lymphocyte proliferation through its effects on processes involved in early cellular activation, providing one possible mechanism to explain the beneficial effects of tomato-rich diets against cardiovascular disease.

IL-2 regulates expression of C-MAF in human CD4 T cells

Blockade of IL-2R with humanized anti-CD25 Abs, such as daclizumab, inhibits Th2 responses in human T cells. Recent murine studies have shown that IL-2 also plays a significant role in regulating Th2 cell differentiation by activated STAT5. To explore the role of activated STAT5 in the Th2 differentiation of primary human T cells, we studied the mechanisms underlying IL-2 regulation of C-MAF expression. Chromatin immunoprecipitation studies revealed that IL-2 induced STAT5 binding to specific sites in the C-MAF promoter. These sites corresponded to regions enriched for markers of chromatin architectural features in both resting CD4 and differentiated Th2 cells. Unlike IL-6, IL-2 induced C-MAF expression in CD4 T cells with or without prior TCR stimulation. TCR-induced C-MAF expression was significantly inhibited by treatment with daclizumab or a JAK3 inhibitor, R333. Furthermore, IL-2 and IL-6 synergistically induced C-MAF expression in TCR-activated T cells, suggesting functional cooperation between these cytokines. Finally, both TCR-induced early IL4 mRNA expression and IL-4 cytokine expression in differentiated Th2 cells were significantly inhibited by IL-2R blockade. Thus, our findings demonstrate the importance of IL-2 in Th2 differentiation in human T cells and support the notion that IL-2R-directed therapies may have utility in the treatment of allergic disorders.

Stimulation-dependent induction of CD154 on a subset of CD4+ FoxP3+ T-regulatory cells

CD40-ligand/CD154 is predominantly expressed on activated CD4 T cells and plays a central role in regulating CD4 T-cell-dependent responses. To define the relative abilities of CD4 T-cell functional subsets in the induction of CD154--specifically FoxP3- effector, versus FoxP3+ regulatory, CD4 T cells--multiple CD4 T cell preparations were isolated from B6 and B6.FoxP3-GFP mice and stimulated in vitro to examine the kinetics of stimulation-dependent CD154 expression. CD154 was induced in 40-60% of total CD4 T cells in various cell preparations. However, despite similar kinetics of CD154-induced expression, the average percentage of CD154 expression among CD4+ FoxP3+ T regulatory (Treg) cells was only about 4-9%. Such differential, stimulation-dependent CD154 induction by total CD4+ T cells versus CD4+ FoxP3+ Treg cells was consistent, despite multiple stimulation conditions utilizing a variety of cell preparations of different composition. Similar induction of CD154 occurred irrespective of whether the CD4+ FoxP3+ Treg cells were first sorted to 98% purity and stimulated in vitro alone, or stimulated as non-purified cells in the presence of CD4+ FoxP3- T effector cells, suggesting that CD154 induction by CD4+ FoxP3+ Treg cells is regulated by cell-intrinsic mechanisms. Differential CD154 induction may be a key factor in determining the distinguishable functions of FoxP3- T-effector, versus FoxP3+ Treg, CD4+ T cells.

Stimulation-dependent induction of CD154 on a subset of CD4+ FoxP3+ T-regulatory cells

CD40-ligand/CD154 is predominantly expressed on activated CD4 T cells and plays a central role in regulating CD4 T-cell-dependent responses. To define the relative abilities of CD4 T-cell functional subsets in the induction of CD154--specifically FoxP3- effector, versus FoxP3+ regulatory, CD4 T cells--multiple CD4 T cell preparations were isolated from B6 and B6.FoxP3-GFP mice and stimulated in vitro to examine the kinetics of stimulation-dependent CD154 expression. CD154 was induced in 40-60% of total CD4 T cells in various cell preparations. However, despite similar kinetics of CD154-induced expression, the average percentage of CD154 expression among CD4+ FoxP3+ T regulatory (Treg) cells was only about 4-9%. Such differential, stimulation-dependent CD154 induction by total CD4+ T cells versus CD4+ FoxP3+ Treg cells was consistent, despite multiple stimulation conditions utilizing a variety of cell preparations of different composition. Similar induction of CD154 occurred irrespective of whether the CD4+ FoxP3+ Treg cells were first sorted to 98% purity and stimulated in vitro alone, or stimulated as non-purified cells in the presence of CD4+ FoxP3- T effector cells, suggesting that CD154 induction by CD4+ FoxP3+ Treg cells is regulated by cell-intrinsic mechanisms. Differential CD154 induction may be a key factor in determining the distinguishable functions of FoxP3- T-effector, versus FoxP3+ Treg, CD4+ T cells.

The role of monoclonal antibodies in the treatment of severe asthma

A number of therapeutic agents are available for the treatment of asthma, including inhaled corticosteroids, long- and short-acting beta-agonists, leukotriene-modifying agents, long- and short-acting anticholinergic agents, chromones, theophylline, allergen immunotherapy, and oral corticosteroid therapy. All available therapies, despite their proven efficacy, are purely symptomatic including the topical steroids. This issue has led to the development of several biologic agents to aid in asthma management and to potentially alter the course of the disease by interfering with specific aspects of inflammation which may modify remodeling in the airways. Monoclonal antibodies have offered a class of therapeutic agents that enhance treatment options for patients with moderate-to-severe persistent asthma. As such, this article provides an overview of present and future monoclonal antibody therapies for the treatment of patients with severe asthma.

The role of anti-inflammatory agents in age-related macular degeneration (AMD) treatment

Although age-related macular degeneration (AMD) is not a classic inflammatory disease like uveitis, inflammation has been found to have an important role in disease pathogenesis and progression. Innate immunity and autoimmune components, such as complement factors, chemokines, cytokines, macrophages, and ocular microglia, are believed to be heavily involved in AMD development. Targeting these specific inflammatory molecules has recently been explored in an attempt to better understand and treat AMD. Although antivascular endothelial growth factor therapy is the first line of defence against neovascular AMD, anti-inflammatory agents such as corticosteroids, nonsteroidal anti-inflammatory drugs (NSAIDs), immunosuppressive agents (eg, methotrexate and rapamycin), and biologics (eg, infliximab, daclizumab, and complement inhibitors) may provide an adjunct or alternative mechanism to suppress the inflammatory processes driving AMD progression. Further investigation is required to evaluate the long-term safety and efficacy of these drugs for both neovascular and non-neovascular AMD.

Epigallocatechin-3-gallate directly suppresses T cell proliferation through impaired IL-2 utilization and cell cycle progression

Previously, we demonstrated that in vitro epigallocatechin-3-gallate (EGCG) supplementation inhibited T cell response in mouse spleen cells. In this study, we confirmed this effect of EGCG in mice fed 0.3% EGCG for 6 wk. A coculture with all the combinations of preincubating antigen-presenting cells and T cells with or without EGCG showed that EGCG suppressed antigen-induced T cell proliferation, mainly through a direct effect on T cells. To determine the mechanisms for this effect of EGCG, we stimulated purified mouse T cells with anti-CD3/CD28 in the presence of EGCG (2.5-15 micromol/L) and found that EGCG dose-dependently inhibited cell division and cell cycle progression and this effect of EGCG was more pronounced in CD4(+) than in CD8(+) T cells. Interleukin (IL)-2 concentrations in EGCG-treated cell cultures showed no difference up to 24 h but were higher in the cultures at 48 h compared with the untreated control cells. However, intracellular staining showed no difference between EGCG-treated and untreated control cells in IL-2 synthesis, but EGCG-treated cells expressed less IL-2 receptor (IL-2R) compared with untreated control cells. EGCG did not affect mRNA expression of IL-2 and IL-2R. These results indicate that EGCG-induced IL-2 accumulation in 48 h cultures is due to its reduced utilization. In summary, EGCG directly inhibits T cell proliferative response to both polyclonal and antigen-specific stimulation. CD4(+) cells are more responsive to EGCG than CD8(+) cells. Future studies should determine the effect of EGCG on CD4(+) cell subsets to assess its application in T cell-mediated autoimmune diseases.

Human CD14hi monocytes and myeloid dendritic cells provide a cell contact-dependent costimulatory signal for early CD40 ligand expression

CD40L on CD4(+) T cells plays a vital role in the activation of antigen-presenting cells, thus catalyzing a positive feedback loop for T-cell activation. Despite the pivotal juxtaposition of CD40L between antigen-presenting cells and T-cell activation, only a T-cell receptor stimulus is thought to be required for early CD40L surface expression. We show, for the first time, that CD40L expression on peripheral blood CD4(+) T cells is highly dependent on a cell-cell interaction with CD14(hi)CD16(-) monocytes. Interactions with ICAM-1, LFA-3, and to a lesser extent CD80/CD86 contribute to this enhancement of CD40L expression but are not themselves sufficient. The contact-mediated increase in CD40L expression is dependent on new mRNA and protein synthesis. Circulating myeloid dendritic cells also possess this costimulatory activity. By contrast, CD14(lo)CD16(+) monocytes, plasmacytoid dendritic cells, B-cell lymphoma lines, and resting, activated, and Epstein-Barr virus-immortalized primary B cells all lack the capacity to up-regulate early CD40L. The latter indicates that a human B cell cannot activate its cognate T cell to deliver CD40L-mediated help. This finding has functional implications for the role of biphasic CD40L expression, suggesting that the early phase is associated with antigen-presenting cell activation, whereas the late phase is related to B-cell activation.

Induction therapy: why, when, and which agent?

The long-term outcome of paediatric transplantation has improved over the last decade with an increase in the armamentarium of immunosuppressive agents. However, the battle against the hostile immune response at the time of and after transplantation continues. Induction therapy can reduce early injury, to optimize the long-term allograft survival. The goal of induction immunosuppression in paediatric transplantation is to permit the use of lower doses of maintenance immunosuppressive agents without increased rates of acute allograft rejection and chronic allograft damage. The aim of this review is to summarize the current literature relating to the use of antibody agents for induction in paediatric solid organ transplantation.

T cell recognition of self-antigen presenting cells by protein transfer assay reveals a high frequency of anti-myelin T cells in multiple sclerosis

Although peripheral blood myelin-autoreactive T cells are thought to play a key role in multiple sclerosis, they are generally considered to have qualitative differences rather than quantitative ones when compared to those found in healthy individuals. Here, we revisited the assessment of myelin-autoreactive T cells in a new approach based on their combined ability to acquire membrane proteins from autologous antigen presenting cells, and to respond to whole myelin extract as the stimulating autoantigen. Using this approach, the myelin-autoreactive T cell frequency in patients with multiple sclerosis was found to be unexpectedly high (n = 22, subtracted values median 2.08%, range 0-6%; background median 1%, range 0-4%) and to exceed that of age/gender-matched healthy individuals significantly (n = 18, subtracted values median 0.1%, range 0-5.3%, P < 0.0001; background median 1.45%, range 0.1-4%). Higher anti-myelin autoreactivity was stable in patients with multiple sclerosis after several months. These data correlated with whole myelin-induced gamma interferon-enzyme-linked immunosorbent spot assay performed under the same conditions, although the values obtained with enzyme-linked immunosorbent spot assay under all conditions were 58 times lower than with this new method. The myelin-autoreactive T cells were memory T cells expressing CD40L with a CD62(low) phenotype, suggesting their ability for homing to tissues. Collectively, these new data show a higher frequency of autoreactive T cells during multiple sclerosis than in age/gender-matched healthy individuals, and support an autoimmune aetiology in multiple sclerosis.

Daclizumab in active relapsing multiple sclerosis (CHOICE study): a phase 2, randomised, double-blind, placebo-controlled, add-on trial with interferon beta

BACKGROUND

Daclizumab, a humanised monoclonal antibody, reduced multiple sclerosis disease activity in previous non-randomised studies. We aimed to assess whether daclizumab reduces disease activity in patients with active relapsing multiple sclerosis who are receiving interferon beta treatment.

METHODS

We did a phase 2, randomised, double-blind, placebo-controlled study at 51 centres in the USA, Canada, Germany, Italy, and Spain. Patients with active relapsing multiple sclerosis who were taking interferon beta were randomly assigned to receive add-on subcutaneous daclizumab 2 mg/kg every 2 weeks (interferon beta and high-dose daclizumab group), daclizumab 1 mg/kg every 4 weeks (interferon beta and low-dose daclizumab group), or interferon beta and placebo for 24 weeks. The randomisation scheme was generated by Facet Biotech. All patients and assessors were masked to treatment with the exception of Facet Biotech bioanalysts who prepared data for the data safety monitoring board or generated pharmacokinetic or pharmacodynamic data, a drug accountability auditor, and the site pharmacist. The primary endpoint was total number of new or enlarged gadolinium contrast-enhancing lesions measured on brain MRI scans every 4 weeks between weeks 8 and 24. Effects of daclizumab on prespecified subsets of lymphocytes and quantitative T-cell proliferative response were assessed in an exploratory pharmacodynamic substudy. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00109161.

FINDINGS

From May, 2005, to March, 2006, 288 patients were assessed for eligibility, and 230 were randomly assigned to receive interferon beta and high-dose daclizumab (n=75), interferon beta and low-dose daclizumab (n=78), or interferon beta and placebo (n=77). The adjusted mean number of new or enlarged gadolinium contrast-enhancing lesions was 4.75 in the interferon beta and placebo group compared with 1.32 in the interferon beta and high-dose daclizumab group (difference 72%, 95% CI 34% to 88%; p=0.004) and 3.58 in the interferon beta and low-dose daclizumab group (25%, -76% to 68%; p=0.51). In the pharmacodynamic substudy, daclizumab was not associated with significant changes in absolute numbers of T cells, B cells, or natural killer cells, or T-cell proliferative response compared with interferon beta alone. The number of CD56(bright) natural killer cells was seven to eight times higher in both daclizumab groups than in the interferon beta and placebo group (interferon beta and low-dose daclizumab group p=0.002; interferon beta and high-dose daclizumab group p<0.0001). Common adverse events were equally distributed across groups.

INTERPRETATION

Add-on daclizumab treatment reduced the number of new or enlarged gadolinium contrast-enhancing lesions compared with interferon beta alone and might reduce multiple sclerosis disease activity to a greater extent than interferon beta alone.

FUNDING

Facet Biotech and Biogen Idec.

The human alloreactive CD4+ T-cell repertoire is biased to a Th17 response and the frequency is inversely related to the number of HLA class II mismatches

Estimates of precursor frequency and assessment of functional characteristics of alloreactive CD4+ T cells are all biased by the need for long-term culture. In this study, direct visualization of human alloreactive CD4+ T cells on the single-cell level was achieved using cell surface expression of CD154 as a tool for identification. The average frequency of alloreactive CD154+CD4+ T cells among peripheral blood CD4+ T cells was 0.1%, with half of the cells displaying a naive phenotype. The proliferation capacity and expression of cytokines after allogeneic stimulation resided in these CD154+CD4+ T cells. The repertoire of alloreactive CD4+ T cells was biased to a Th17 response, and on average 24% of alloreactive CD154+CD4+ memory T cells produced interleukin-17 (IL-17) after polyclonal stimulation. Unexpectedly, mixed cell cultures from human leukocyte antigen (HLA)-identical donors also generated alloreactive CD154+CD4+ T cells and yielded the highest frequency compared with HLA-nonidentical combinations. Therefore, reactivity to minor histocompatibility antigens between HLA-identical subjects appears to be relatively common. Alloreactive HLA-identical T cells did not proliferate or express cytokines, but were driven to proliferation in the presence of exogenous IL-2.

Immunological and histochemical analyses of cerebrospinal fluid and peripheral blood from patients with neurological and psychiatric disorders

Epidemiological, clinical and post mortem studies indicate that inflammatory and immune reactions are involved in the pathomechanisms of affective and schizophrenic spectrum disorders. However, in psychiatric patients, only sporadic investigation on immunochemistry has been performed and information about immunofunction derived by investigation of immunocompetent cells in the CSF is not available to date. Here we present an interdisciplinary work of neurologists, psychiatrists and hemato-immunologists focusing on the immunology of psychiatric and neurological disorders. In a first study including 63 patients with therapy resistant affective and schizophrenic spectrum disorders we applied conventional, validated neurological CSF investigation such as analysis of albumin, IgG, IgA, IgM, oligoclonal IgG and specific antibodies, cell count and interpreted the data by Reibergrams. In a second study, we applied the highly sensitive and specific multicolour flowcytometry of paired samples of CSF and peripheral blood cells to characterize the immunostatus of psychiatric and neurological patients. We demonstrate that flowcytometry technology constitutes an appropriate method to investigate subsets of lymphocytes even with low CSF cell numbers, and therefore as a promising diagnostic tool for routine purposes in the differential diagnosis of psychiatric diseases. Furthermore, knowledge of the frequencies of T cell subsets such as the T regulatory cell type might open new avenues to models of psychiatric and neurological diseases as well as diagnostic and monitoring implications.

Unravelling the mechanisms of help for CD8+ T cell responses

CD8+ T cells are critically important for immune defense against many viral and bacterial pathogens, and are also key components of cancer immunotherapy. Help from CD4+ T cells is usually essential for optimal CD8+ T cell responses, driving the primary response, the survival of memory cells, and the generation of protective and therapeutic immunity. Understanding the mechanisms of help is thus essential for vaccine design, and for restoring protective immunity in immunosuppressed individuals. Our laboratory has developed an immunization protocol using peptide-pulsed dendritic cells to stimulate help-dependent primary, memory, and secondary CD8+ T cell responses. We have used gene-targeted and T cell receptor transgenic mice to identify two distinct pathways that generate help-dependent and help-independent CD8+ T cell responses, respectively, and are now starting to define the molecular mechanisms underlying these two pathways.

The effect of the JAK inhibitor CP-690,550 on peripheral immune parameters in stable kidney allograft patients

INTRODUCTION

CP-690,550 inhibits Janus kinase 3 (JAK3) which mediates signal transduction of receptors of the common gamma-chain cytokines. These cytokines play key roles in lymphocyte function and homeostasis. As part of a phase 1 trial, we evaluated the effect of CP-690,550 on immune parameters.

MATERIAL

Stable kidney transplant recipients (n=8) receiving mycophenolate mofetil and prednisolone were treated with CP-690,550, 30 mg twice daily orally for 29 days. Blood samples were collected on days 1 (before first dose), 15, 29 (end of treatment), and 57.

RESULTS

Two patients experienced minor infections (one urinary tract infection and one mild respiratory tract infection). Leukocyte counts remained stable, whereas a mean decrease in hemoglobulin of 8% was measured (P=0.01). CP-690,550 treatment for 29 days resulted in statistically significant changes in the number of circulating CD19+ B cells (P=0.05), CD3- CD16+ CD56+ natural killer-cells (P<0.01), and CD4+ CD25bright+ T cells (P=0.05; one-way analysis of variance). After CP-690,550 treatment on day 15 the number of B cells increased by a mean of 100%, (P=0.04), whereas those of natural killer cells and CD4+ CD25bright+ T cells decreased by 65% (P=0.001) and 38% (P=0.03, t test), respectively, from pretreatment baseline. However, the regulatory capacities of the residual CD4+ CD25bright+ T cells remained unchanged pre- and posttreatment. In addition, in the presence of CP-690,550, the interferon-[gamma] production capacity of peripheral blood mononuclear cells was reduced by 39% (median) compared with predose baseline (P=0.01).

CONCLUSIONS

These findings demonstrate the role of JAK3 in the homeostasis and function of select lymphocyte subpopulations. JAK3 inhibition may provide a novel mechanism for the modulation of allogeneic responses in patients after transplantation.

Flow cytometric analysis of T cell subsets in paired samples of cerebrospinal fluid and peripheral blood from patients with neurological and psychiatric disorders

Recent studies suggest inflammatory mechanisms involved in the pathogenesis of major psychiatric disorders (MPD). T cells play a major role during inflammation, but little is known about T cell subpopulations in the cerebrospinal fluid (CSF). We investigated the frequency of cells positive for the surface markers CD4, CD8, CD25, CD45, CD69, and CD127 in 45 paired cerebrospinal fluid (CSF) and peripheral blood (PB) samples by multiparameter flow cytometry from patients with MPD of the schizophrenic and affective spectrum with normal CSF cell counts and compared them with those from patients with non-inflammatory (NIND), chronic inflammatory (CIND) neurological disorders, and meningitis (MEN). In MEN patients, CD4+ cell frequency in PB, but not in CSF, was significantly increased as compared to CIND and NIND. No difference between patient groups was observed for CD8+. CD4+CD45RO+ double positive cells in PB were significantly lower in CIND than in MEN or NIND. The frequency of CD4+CD25+ cells in PB was significantly higher in MEN than in MPD or CIND. For CSF, the percentage of CD4+CD127(dim) cells was significantly lower in MEN than in MPD. CD4+CD127(dim) in PB and CSF showed overlapping characteristic clusters between MPD and CIND and MEN patients. Overall, the hypothesis of low degree inflammation in a subgroup of MPD is supported. The analysis of lymphocyte subsets in PB and CSF constitutes a novel promising tool to understand underlying pathomechanisms in psychiatric and neurological disorders on an individual case level.

Cutting edge: CD4+ T cell-derived IL-2 is essential for help-dependent primary CD8+ T cell responses

CD4(+) T cell help is essential for primary CD8(+) T cell responses to noninflammatory Ags. IL-2 is one of the principal cytokines made by naive CD4(+) T cells, and we show in this study that it is an essential component of help. Adoptively transferred naive CD4(+) TCR-transgenic OT-II cells supported endogenous primary CD8(+) T cell responses, but IL-2-deficient OT-II cells were unable to provide help, although they responded to Ag in vivo and up-regulated CD40 ligand in vitro. Wild -type OT-II cells helped endogenous CD8(+) T cell responses in IL-2-deficient mice, but not in IL-2Ralpha-deficient mice. Thus, CD4(+) T cell-derived IL-2 is essential for CD8(+) T cell responses to noninflammatory, cell-associated Ags. We suggest that it is also a critical component of help for CD8(+) T cell responses to pathogens, because protective memory also requires CD8(+) T cell stimulation by IL-2 during priming.

Foal monocyte-derived dendritic cells become activated upon Rhodococcus equi infection

Susceptibility of foals to Rhodococcus equi pneumonia is exclusive to the first few months of life. The objective of this study was to investigate the immediate immunologic response of foal and adult horse antigen-presenting cells (APCs) upon infection with R. equi. We measured the activation of the antigen-presenting major histocompatibility complex (MHC) class II molecule, costimulatory molecules CD40 and CD86, the cytokine interleukin-12 (IL-12), and the transcriptional factor interferon regulatory factor 1 (IRF-1) in monocyte-derived macrophages (mMOs) and dendritic cells (mDCs) of adult horses and foals of different ages (from birth to 3 months of age) infected with virulent R. equi or its avirulent, plasmid-cured derivative. Infection with virulent or avirulent R. equi induced (P <or= 0.01) the expression of IL-12p35 and IL-12p40 mRNAs in foal mMOs and mDCs at different ages. This response was likely mediated by the higher (P=0.008) expression of IRF-1 in foal mDCs at birth than in adult horse mDCs. R. equi infection promoted comparable expression of costimulatory molecules CD86 and CD40 in foal and adult horse cells. The cytokine and costimulatory response by foal mDCs was not accompanied by robust MHC class II molecule expression. These data suggest that foal APCs detect the presence of R. equi and respond with the expression of the Th1-inducing cytokine IL-12. Nevertheless, there seems to be a limitation to MHC class II molecule expression which we hypothesize may compromise the efficient priming of naïve effector cells in early life.

CD28 and inducible costimulator (ICOS) signalling can sustain CD154 expression on activated T cells

The biological outcome of receptor-mediated signalling often depends on the duration of engagement. Because CD40 signalling is controlled by the regulated expression of its ligand, CD154, the mechanisms that regulate CD154 expression probably determine the strength and duration of CD40 signalling. Here, we demonstrate that CD154 expression on the surface of mouse CD4 T cells can be separated into an early phase, occurring between 0 and 24 hr after T-cell activation, and a later extended phase, occurring after 24 hr. The early phase of CD154 expression did not require costimulation and was probably influenced by the strength of T-cell receptor (TCR) signalling alone. However, later CD154 expression was highly dependent on costimulation through either CD28 or inducible costimulator (ICOS). Although CD28 signalling interleukin (IL)-2 secretion, ICOS not, suggesting that costimulation enhance CD154 expression independently of IL-2 production. In fact, anti-CD28 treatment could still induce late-phase CD154 on anti-CD3-stimulated CD4 T cells expressing a mutated form of CD28 that not lead to the induction of IL-2. However, this CD154 induction was somewhat weaker than that of wild-type CD28-expressing cells, suggesting that direct signalling and IL-2-mediated signalling co-operatively responsible for the levels of CD154 induced by CD28. Finally, we show that the second phase of CD154 expression negatively regulated B-cell terminal differentiation and antibody secretion. These results demonstrate that TCR signalling and costimulation each regulate different phases of CD154 expression and control the biological outcome of CD40 signalling on B cells.

Daclizumab improves asthma control in patients with moderate to severe persistent asthma: a randomized, controlled trial

RATIONALE

Airway inflammation in asthma is associated with increased activated CD25(+) T cells, IL-2, and soluble IL-2 receptors (IL-2Rs).

OBJECTIVES

A randomized, double-blinded, placebo-controlled study was used to evaluate the safety and efficacy of daclizumab, a humanized IgG1 monoclonal antibody against the IL-2R alpha chain (CD25) of activated lymphocytes, in adults with moderate to severe persistent asthma.

METHODS

Patients with obstructive pulmonary functions, despite inhaled corticosteroids (ICS), were switched to equivalent dose inhaled triamcinolone acetate acetonide (TAA). Patients dependent on ICS were randomized (3:1) to daclizumab (intravenous loading dose, 2 mg/kg, then 1 mg/kg) or placebo every 2 weeks, added to stable-dose TAA through Week 12 (Treatment Period 1). Over Weeks 12-20 (Treatment Period 2), patients tapered TAA while on the study drug, and were followed for 16 weeks off the study drug.

MEASUREMENTS AND MAIN RESULTS

Among 115 evaluable patients (88 daclizumab, 27 placebo), groups had similar age, disease duration, and length of ICS use. During Treatment Period 1, daclizumab improved FEV(1) (daclizumab, 4.4 +/- 1.80% vs. placebo, 1.5 +/- 2.39%; P = 0.05), and reduced daytime asthma symptoms (P = 0.018) and short-acting inhaled beta(2)-agonist use (P = 0.009). Daclizumab treatment prolonged time to exacerbation (P = 0.024). Adverse events were evenly distributed between groups, although there were more serious adverse events in the patients treated with daclizumab.

CONCLUSIONS

Daclizumab improved pulmonary function and asthma control in patients with moderate to severe chronic asthma inadequately controlled on ICS. The mechanism of action likely involves inhibition of proinflammatory cytokine generation by IL-2R blockade in activated T cells. Clinical trial registered with www.clinicaltrials.gov (NCT00028288).

Effects of interleukin-12 and interleukin-15 on measles-specific T-cell responses in vaccinated infants

Understanding the infant host response to measles vaccination is important because of their increased mortality from measles and the need to provide effective protection during the first year of life. Measles-specific T and B-cell responses are lower in infants after measles vaccination than in adults. To define potential mechanisms, we investigated age-related differences in measles-specific T-cell proliferation, CD40-L expression, and IFN-gamma production after measles immunization, and the effects of rhIL-12 and rhIL-15 on these responses. Measles-specific T-cell proliferation and mean IFN-gamma release from infant PBMCs were significantly lower when compared with responses of vaccinated children and adults. Infant responses increased to ranges observed in children and adults when both rhIL-12 and rhIL-15 were added to PBMC cultures. Furthermore, a significant rise in T-cell proliferation and IFN-gamma release was observed when infant PBMCs were stimulated with measles antigen in the presence of rhIL-12 and rhIL-15 compared to measles antigen alone. CD40-L expression by infant and adult T cells stimulated with measles antigen was comparable, but fewer infant CD40-L(+) T cells expressed IFN-gamma. These observations suggest that lower measles-specific T-cell immune responses elicited by measles vaccine in infants may be due to diminished levels of key cytokines.

Age-associated changes in immune and inflammatory responses: impact of vitamin E intervention

Aging is associated with dysregulated immune and inflammatory responses. Declining T cell function is the most significant and best-characterized feature of immunosenescence. Intrinsic changes within T cells and extrinsic factors contribute to the age-associated decline in T cell function. T cell defect seen in aging involves multiple stages from early receptor activation events to clonal expansion. Among extrinsic factors, increased production of T cell-suppressive factor PGE(2) by macrophages (Mphi) is most recognized. Vitamin E reverses an age-associated defect in T cells, particularly naïve T cells. This effect of vitamin E is also reflected in a reduced rate of upper respiratory tract infection in the elderly and enhanced clearance of influenza infection in a rodent model. The T cell-enhancing effect of vitamin E is accomplished via its direct effect on T cells and indirectly by inhibiting PGE(2) production in Mphi. Up-regulated inflammation with aging has attracted increasing attention as a result of its implications in the pathogenesis of diseases. Increased PGE(2) production in old Mphi is a result of increased cyclooxygenase 2 (COX-2) expression, leading to higher COX enzyme activity, which in turn, is associated with the ceramide-induced up-regulation of NF-kappaB. Similar to Mphi, adipocytes from old mice have a higher expression of COX-2 as well as inflammatory cytokines IL-1beta, IL-6, and TNF-alpha, which might also be related to elevated levels of ceramide and NF-kappaB activation. This review will discuss the above age-related immune and inflammatory changes and the effect of vitamin E as nutritional intervention with a focus on the work conducted in our laboratory.

High-dose humanized anti-IL-2 receptor alpha antibody (daclizumab) for the treatment of active, non-infectious uveitis

PURPOSE

This study was designed to provide preliminary data regarding the safety and efficacy of high-dose humanized anti-IL-2 receptor (daclizumab) therapy for the treatment of active intermediate, posterior or panuveitis.

METHODS

Five patients were recruited into this non-randomized, prospective pilot study of high-dose intravenous induction daclizumab therapy given at doses of 8mg/kg at day 0 and 4mg/kg at day 14. Patients who did not meet a safety endpoint at the 3-week follow-up evaluation were given the option of continuing therapy with subcutaneous daclizumab at 2mg/kg every 4 weeks for 52 weeks. The primary outcome assessed was a two-step decrease in vitreous haze at day 21. Secondary outcomes evaluated included best-corrected visual acuity, retinal thickness as measured by optical coherence tomography, retinal vascular leakage assessed by fluorescein angiography, anterior chamber and vitreous cellular inflammation.

RESULTS

Four male patients and one female patient were enrolled. Diagnoses included birdshot retinochoroidopathy (two patients), Vogt-Koyanagi-Harada's disease, bilateral idiopathic panuveitis and bilateral idiopathic intermediate uveitis. By the 4th week, four of five patients demonstrated a two-step decrease in vitreous haze. The other participant did not meet this criterion until week 20, but all five patients maintained stability in vitreous haze grade throughout their follow-up periods. At enrollment, mean visual acuity (10 eyes in 5 patients) was 69.2 ETDRS letters and following treatment was 78.2 letters (p<0.12). Anterior chamber cell, vitreous cell, and vitreous haze also improved in the majority of eyes. Adverse events were generally mild except for one episode of left-lower lobe pneumonia requiring hospitalization and treatment.

CONCLUSION

This is the first demonstration that high-dose daclizumab can reduce inflammation in active uveitis. Daclizumab was well tolerated but there may be a potential increased risk of infection associated with immunosuppression. All five patients demonstrated a decrease in vitreous haze and measures of intraocular inflammation at final follow-up. The results of this small, non-randomized pilot study support the consideration of high-dose daclizumab therapy in cases of active posterior uveitis.

Age-related macular degeneration and the immune response: implications for therapy

PURPOSE

To review the available information concerning the immune mediation of age-related macular degeneration (AMD) and to speculate on proposed mechanisms and immunotherapy.

DESIGN

Interpretative essay.

METHODS

Literature review and interpretation.

RESULTS

An ever-growing body of evidence is gathering concerning the role of the immune system in AMD. Evidence to date suggests that the underlying mechanism leading to AMD is the decline of the ocular downregulatory immune environment. The subsequent activation of the immune system would lead to T-cell sensitization. When combined with local antiangiogenic therapy, several existing immunotherapies may be used to downregulate the immune response, potentially leading to a more efficient inhibition of choroidal neovascularization.

CONCLUSIONS

The loss of the downregulatory immune environment is central to the development of AMD, permitting activation of the immune system. If so, immunotherapy could positively alter the course of the disease.

Direct inhibition of CD40L expression can contribute to the clinical efficacy of daclizumab independently of its effects on cell division and Th1/Th2 cytokine production

Humanized anti-CD25 antibodies (eg, daclizumab) have been successfully used to treat several autoimmune diseases. Paradoxically, IL-2 blockade in mice can induce autoimmunity. An interspecies difference in the relative contribution of IL-2 to CD25(+) T regulatory cell (CD25(+)Treg) versus CD25(+) effector cell function might explain this conundrum. Consistent with this are reports that daclizumab inhibits human CD25(+) effector cell cytokine production by blocking the expression of CD40L. However, in mice, IL-4 and IL-12 regulate CD40L expression. As human Th1/Th2 cytokine production is also dependent on IL-2, daclizumab's inhibition of CD40L expression could be due to an indirect, rather than a direct, effect of IL-2. Here, we clarify the mechanisms underlying CD40L expression. In contrast to the mouse, human CD40L is regulated by CD28 signaling and IL-2, not the principal Th1/Th2-polarizing cytokines. We find that CD40L is expressed on naive and memory cells and inhibited by daclizumab independently of cell division. Collectively, our results indicate that daclizumab could inhibit CD25(+) effector T-cell function in vivo by directly blocking CD40L expression. This difference between mice and human may help explain the paradoxical effects of IL-2R blockade in the 2 species.

SAP regulates T cell-mediated help for humoral immunity by a mechanism distinct from cytokine regulation

X-linked lymphoproliferative disease is caused by mutations affecting SH2D1A/SAP, an adaptor that recruits Fyn to signal lymphocyte activation molecule (SLAM)-related receptors. After infection, SLAM-associated protein (SAP)-/- mice show increased T cell activation and impaired humoral responses. Although SAP-/- mice can respond to T-independent immunization, we find impaired primary and secondary T-dependent responses, with defective B cell proliferation, germinal center formation, and antibody production. Nonetheless, transfer of wild-type but not SAP-deficient CD4 cells rescued humoral responses in reconstituted recombination activating gene 2-/- and SAP-/- mice. To investigate these T cell defects, we examined CD4 cell function in vitro and in vivo. Although SAP-deficient CD4 cells have impaired T cell receptor-mediated T helper (Th)2 cytokine production in vitro, we demonstrate that the humoral defects can be uncoupled from cytokine expression defects in vivo. Instead, SAP-deficient T cells exhibit decreased and delayed inducible costimulator (ICOS) induction and heightened CD40L expression. Notably, in contrast to Th2 cytokine defects, humoral responses, ICOS expression, and CD40L down-regulation were rescued by retroviral reconstitution with SAP-R78A, a SAP mutant that impairs Fyn binding. We further demonstrate a role for SLAM/SAP signaling in the regulation of early surface CD40L expression. Thus, SAP affects expression of key molecules required for T-B cell collaboration by mechanisms that are distinct from its role in cytokine regulation.