Changes In Surface Marker Expression Research Articles

Novel genetically glycoengineered human dendritic cell model reveals regulatory roles of α2,6-linked sialic acids in DC activation of CD4+ T cells and response to TNFα.

Dendritic cells (DCs) are central for the initiation and regulation of appropriate immune responses. While several studies suggest important regulatory roles of sialoglycans in DC biology, our understanding is still inadequate primarily due to a lack of appropriate models. Previous approaches based on enzymatic- or metabolic-glycoengineering and primary cell isolation from genetically modified mice have limitations related to specificity, stability, and species differences. This study addresses these challenges by introducing a workflow to genetically glycoengineer the human DC precursor cell line MUTZ-3, described to differentiate and maturate into fully functional dendritic cells, using CRISPR-Cas9, thereby providing and validating the first isogenic cell model for investigating glycan alteration on human DC differentiation, maturation, and activity. By knocking out (KO) the ST6GAL1 gene, we generated isogenic cells devoid of ST6GAL1-mediated α(2,6)-linked sialylation, allowing for a comprehensive investigation into its impact on DC function. Glycan profiling using lectin binding assay and functional studies revealed that ST6GAL1 KO increased the expression of important antigen presenting and co-stimulatory surface receptors and a specifically increased activation of allogenic human CD4 + T cells. Additionally, ST6GAL1 KO induces significant changes in surface marker expression and cytokine response to TNFα-induced maturation, and it affects migration and the endocytic capacity. These results indicate that genetic glycoengineering of the isogenic MUTZ-3 cellular model offers a valuable tool to study how specific glycan structures influence human DC biology, contributing to our understanding of glycoimmunology.

IMPDH inhibition activates TLR-VCAM1 pathway and suppresses the development of MLL-fusion leukemia.

Inosine monophosphate dehydrogenase (IMPDH) is a rate-limiting enzyme in de novo guanine nucleotide synthesis pathway. Although IMPDH inhibitors are widely used as effective immunosuppressants, their antitumor effects have not been proven in the clinical setting. Here, we found that acute myeloid leukemias (AMLs) with MLL-fusions are susceptible to IMPDH inhibitors invitro. We also showed that alternate-day administration of IMPDH inhibitors suppressed the development of MLL-AF9-driven AML invivo without having a devastating effect on immune function. Mechanistically, IMPDH inhibition induced overactivation of Toll-like receptor (TLR)-TRAF6-NF-κB signaling and upregulation of an adhesion molecule VCAM1, which contribute to the antileukemia effect of IMPDH inhibitors. Consequently, combined treatment with IMPDH inhibitors and the TLR1/2 agonist effectively inhibited the development of MLL-fusion AML. These findings provide a rational basis for clinical testing of IMPDH inhibitors against MLL-fusion AMLs and potentially other aggressive tumors with active TLR signaling.

In Vitro Model Systems to Study Human T Cell Development.

Not only is human T cell development characterized by unique changes in surface marker expression, but it also requires specific growth factors and conditions to mimic and study T cell development in vitro. In this chapter, we provide an overview of the specific aspects that need attention when performing T cell differentiation cultures with human hematopoietic and T cell progenitors.

Therapies with CCL25 require controlled release via microparticles to avoid strong inflammatory reactions

BackgroundChemokine therapy with C–C motif chemokine ligand 25 (CCL25) is currently under investigation as a promising approach to treat articular cartilage degeneration. We developed a delayed release mechanism based on Poly (lactic-co-glycolic acid) (PLGA) microparticle encapsulation for intraarticular injections to ensure prolonged release of therapeutic dosages. However, CCL25 plays an important role in immune cell regulation and inflammatory processes like T-cell homing and chronic tissue inflammation. Therefore, the potential of CCL25 to activate immune cells must be assessed more thoroughly before further translation into clinical practice. The aim of this study was to evaluate the reaction of different immune cell subsets upon stimulation with different dosages of CCL25 in comparison to CCL25 released from PLGA particles.ResultsImmune cell subsets were treated for up to 5 days with CCL25 and subsequently analyzed regarding their cytokine secretion, surface marker expression, polarization, and migratory behavior. The CCL25 receptor C–C chemokine receptor type 9 (CCR9) was expressed to a different extent on all immune cell subsets. Direct stimulation of peripheral blood mononuclear cells (PBMCs) with high dosages of CCL25 resulted in strong increases in the secretion of monocyte chemoattractant protein-1 (MCP-1), interleukin-8 (IL-8), interleukin-1β (IL-1β), tumor-necrosis-factor-α (TNF-α) and interferon-γ (IFN-γ), upregulation of human leukocyte antigen-DR (HLA-DR) on monocytes and CD4+ T-cells, as well as immune cell migration along a CCL25 gradient. Immune cell stimulation with the supernatants from CCL25 loaded PLGA microparticles caused moderate increases in MCP-1, IL-8, and IL-1β levels, but no changes in surface marker expression or migration. Both CCL25-loaded and unloaded PLGA microparticles induced an increase in IL-8 and MCP-1 release in PBMCs and macrophages, and a slight shift of the surface marker profile towards the direction of M2-macrophage polarization.ConclusionsWhile supernatants of CCL25 loaded PLGA microparticles did not provoke strong inflammatory reactions, direct stimulation with CCL25 shows the critical potential to induce global inflammatory activation of human leukocytes at certain concentrations. These findings underline the importance of a safe and reliable release system in a therapeutic setup. Failure of the delivery system could result in strong local and systemic inflammatory reactions that could potentially negate the benefits of chemokine therapy.

A Polymorphonuclear Leukocyte Assay to Assess Implant Immunocompatibility.

Polymorphonuclear leukocytes (PMNs) are essential in the first infection and host-versus-graft reactions. Strategies for adequate and standardized assays to test PMN activation by diverse types of matrices such as cardiovascular implants are urgently needed. To overcome this limitation, we established a straightforward PMN activation assay and validated lipopolysaccharide (LPS) as a reliable PMN activator that induces defined changes in surface marker expression and cytokine release. Biological "proof-of-principle" matrices demonstrated the feasibility of this PMN assay. Overall, this assay provides an instrument conducting an initial immunological assessment of biological implants prior their clinical application.

Adipose tissue derived mesenchymal stem cells exhibit a superior immune-modulatoery effect on mature dendritic cells compared to bone marrow derived mesenchymal stem cells

Background & Aim Background The ability of mesenchymal stem cells (MSCs) to interact with immune cells and exert a modulatory effect is the core of cellular therapy approaches. Dendritic cells (DCs), the most potent of antigen presenting cells (APCs), play a key role in T-cell activation and firing immune responses. The direct interaction between MSCs and mature DCs (mDCs) results in attenuation of mDCs' activity and subsequent immune reactions. Aim Bone marrow derived MSCs (BM-MSCs) and adipose tissue derived MSCs (AT- MSCs), are more abundant and easier to harvest compared to other types of MSCs. How BM-MSCs and AT-MSCs affect mDCs can be illustrated with changes in surface marker expression and mDCs secreted cytokines, a focus is needed on changes in mDC gene expression which may help in a better understanding of the interaction process. Methods, Results & Conclusion Methods MSCs were isolated from two adult sources bone marrow and adipose tissue. Monocytes were isolated from peripheral blood to generate mDCs in recommended culture conditions. All cells were characterized by flowcytometry. Multiplex immunoassay was carried out to evaluate the inflammatory cytokines levels. PCR arrays were performed to demonstrate the gene expression profile of mDCs. All tests were performed before and after direct contact co-culture of mDCs with BM-MSCs, and with AT-MSCs. Results The immune-inhibitory effect of both types of MSCs on mDCs was manifested by a decrease in the levels of inflammatory cytokines, and the downregulation of 84 investigated genes responsible for mDC activity in both co-cultures. The fold changes, and fold change ratios from PCR array data clearly demonstrate the superiority of AT-MSCs in inhibiting mDCs immune awakening functions. This finding is supported by previous microarray analysis of the inherent immune-modulatory potential of both types of MSCs, which revealed an advantage for AT-MSCs over BM-MSCs, in terms of the expression magnitude of immune-regulatory genes. Functional annotation clustering and gene ontology demonstrated that all investigated genes participate in response to stimulus (p- value= 4.3 E-26), and that 79.8% (67 out of 84 genes) are significant players in positive regulation of response to stimulus (p-value = 4.3 E-45). Conclusion These findings highlight the outcome of MSCs’ interaction with mDCs on the molecular level. Our data confirm the immune-modulatory properties of MSCs and suggest AT-MSCs as a more effective suppressor of mDCs immune activity than BM-MSCs.

Pericytes secrete pro-regenerative molecules in response to platelet-derived growth factor-BB

Brain pericytes not only maintain the anatomical, biochemical and immune blood–brain barrier, but display features of mesenchymal stem cells (MSCs) in vitro. MSCs have pro-regenerative properties attributed to their secretome. However, whether also brain pericytes possess such pro-regenerative capacities is largely unknown. Here we characterize the secretome and microvesicle (MV) release of human brain pericytes mediated by platelet-derived growth factor-BB (PDGF-BB)/PDGF receptor beta (PDGFRβ) signalling. Upon PDGF-BB, pericytes release not only a plethora of growth factors and a panel of cytokines, but also MVs containing BDNF, FGFb, βNGF, VEGF and PLGF, a response that is specific for PDGFRβ signalling and activation of the ERK 1/2 pathway. In contrast, lipopolysaccharide (LPS), an activator of the innate immune system, stimulates the secretion of much higher amounts of mainly inflammatory cytokines and activates the NFκB pathway. Pericytes change their morphology and undergo opposite changes in surface marker expression, respectively. Our findings provide evidence that the secretome of human brain pericytes varies greatly depending on the exogenous stimulus. The differential secretory functions of pericytes may play an important role in either regulating neuroinflammation or contributing to neurorestoration and identify a possible new target cell for neuroregeneration.

Dimethylfumarate Impairs Neutrophil Functions

Host defense against pathogens relies on neutrophil activation. Inadequate neutrophil activation is often associated with chronic inflammatory diseases. Neutrophils also constitute a significant portion of infiltrating cells in chronic inflammatory diseases, for example, psoriasis and multiple sclerosis. Fumarates improve the latter diseases, which so far has been attributed to the effects on lymphocytes and dendritic cells. Here, we focused on the effects of dimethylfumarate (DMF) on neutrophils. In vitro, DMF inhibited neutrophil activation, including changes in surface marker expression, reactive oxygen species production, formation of neutrophil extracellular traps, and migration. Phagocytic ability and autoantibody-induced, neutrophil-dependent tissue injury ex vivo was also impaired by DMF. Regarding the mode of action, DMF modulates-in a stimulus-dependent manner-neutrophil activation using the phosphoinositide 3-kinase/Akt-p38 mitogen-activated protein kinase and extracellular signal-regulated kinase 1/2 pathways. For in vivo validation, mouse models of epidermolysis bullosa acquisita, an organ-specific autoimmune disease caused by autoantibodies to type VII collagen, were employed. In the presence of DMF, blistering induced by injection of anti-type VII collagen antibodies into mice was significantly impaired. DMF treatment of mice with clinically already-manifested epidermolysis bullosa acquisita led to disease improvement. Collectively, we demonstrate a profound inhibitory activity of DMF on neutrophil functions. These findings encourage wider use of DMF in patients with neutrophil-mediated diseases.

Approaches to Study Human T Cell Development.

Not only is human T cell development characterized by unique changes in surface marker expression, but it also requires specific growth factors and conditions to mimic and study T cell development in vitro. In this chapter, we provide an overview of the specific aspects that need attention when performing T cell differentiation cultures with human progenitors.

Cigarette-smoke-induced priming of neutrophils from smokers and non-smokers for increased oxidative burst response is mediated by TNF-α

In vitro treatment of human peripheral blood neutrophils from smokers and non-smokers with an aqueous cigarette smoke (CS) extract resulted in a concentration-dependent increase in surface expression of CD11b and CD66b and a corresponding decrease of CD62L, together with a concentration-dependent release of MMP-8, MMP-9, and lactoferrin, indicating considerable activation and degranulation. However, the burst response to N-formyl-methionyl-leucyl-phenylalanine (fMLP) was unchanged in CS-stimulated neutrophils from both smokers and non-smokers. When supernatants from CS-treated monocytic MonoMac-6 (MM6) cells were used for activation of neutrophils, concentration-dependent changes in surface marker expression, granule protein release, and the oxidative burst response to fMLP were observed, again with no major differences between smokers and non-smokers. CS-treated MM6 cells released significant amounts of IL-8 and TNF-α into the culture supernatant. However, antibody blocking experiments showed that only TNF-α mediated the increased burst response in neutrophils. These data show that, in the presence of secondary cells, CS is able to prime neutrophils for an increased burst response to fMLP which is mediated by TNF-α, released from the secondary cells in response to CS. Following stimulation with priming agents, peripheral blood neutrophils from healthy smokers show an equal burst response compared to those from non-smokers.

A C-Terminal Acidic Domain Regulates Degradation of the Transcriptional Coactivator Bob1

Bob1 (Obf-1 or OCA-B) is a 34-kDa transcriptional coactivator encoded by the Pou2af1 gene that is essential for normal B-cell development and immune responses in mice. During lymphocyte activation, Bob1 protein levels dramatically increase independently of mRNA levels, suggesting that the stability of Bob1 is regulated. We used a fluorescent protein-based reporter system to analyze protein stability in response to genetic and physiological perturbations and show that, while Bob1 degradation is proteasome mediated, it does not require ubiquitination of Bob1. Furthermore, degradation of Bob1 in B cells appears to be largely independent of the E3 ubiquitin ligase Siah. We propose a novel mechanism of Bob1 turnover in B cells, whereby an acidic region in the C terminus of Bob1 regulates the activity of degron signals elsewhere in the protein. Changes that make the C terminus more acidic, including tyrosine phosphorylation-mimetic mutations, stabilize the instable murine Bob1 protein, indicating that B cells may regulate Bob1 stability and activity via signaling pathways. Finally, we show that expressing a stable Bob1 mutant in B cells suppresses cell proliferation and induces changes in surface marker expression commonly seen during B-cell differentiation.

Diesel exhaust particles modify natural killer cell function and cytokine release

BackgroundNatural killer (NK) cells are an important lymphocyte population in the nasal mucosa and play important roles in linking the innate and the adaptive immune response. Their two main functions are direct cell-mediated cytotoxicity and the release of cytokines. They are important during viral infections and cancer. Due to their location in the nasal mucosa, NK cells are likely exposed to inhaled pollutants, such as diesel exhaust. Whether and how exposure to diesel exhaust particles (DEP) affects NK cell function in the context of viral infections has not been investigated.MethodsNK cells were isolated from peripheral blood obtained from normal healthy volunteers and subsequently stimulated with the viral mimetic polyinosinic:polycytidylic acid (pI:C), DEP, or pI:C+DEP for 18 hours. NK cells were subsequently analyzed for changes in surface marker expression, cytokine production, gene expression changes, and cytotoxic function using flow cytometry, ELISA, qRT-PCR, and cell-mediated cytotoxicity assay, respectively.ResultsStimulation of NK cells with pI:C and pI:C+DEP, but not DEP alone, increased the release of IL-1β, IL-2, IL-4, IL-8, IL-10, IL-12p70, IFN-γ and TNF-α. As compared to pI:C alone or pI:C+DEP, the release of IL-1β, IL-8 and TNF-α was significantly lower after DEP stimulation alone. Stimulation with pI:C alone increased the gene and protein expression of granzyme B and perforin, which was completely blunted by adding DEP. Addition of DEP further reduced CD16 expression in pI:C stimulated cells. Similarly, cell-mediated cytotoxicity was significantly reduced by the addition of DEP.ConclusionsIn the context of viral infection, DEP potentially reduces NK cells' ability to kill virus-infected host cells, in spite of normal cytokine levels, and this may increase susceptibility to viral infections . This reduction in the potential ability of NK cells to kill virus-infected host cells may increase the susceptibility to viral infections after DEP exposure.

A High-Throughput Screen to Identify Compounds Preserving Primary Human AML Stem Cells Ex-Vivo,

Abstract 3587Acute myeloid leukemia (AML) is the second most frequent leukemia in adults with still high relapse rates supposed to be due to a rare population of leukemia stem cells (LSC) within the leukemic bulk not responding to conventional anti-cancer drugs. Engraftment of human leukemic cells in immunocompromised mice mimicking the human disease is considered to prove the existence of stem cells in the sample; however, the engraftment potential of primary human AML cells is usually quickly lost upon ex-vivo culture indicating that LSC have undergone differentiation or apoptosis and thus lost their stem cell properties. This lack of appropriate culture conditions enabling ex-vivo maintenance of primary human LSC is a major obstacle in the development of LSC targeted therapies. Our aim is, therefore, to identify conditions which allow the maintenance and expansion of these rare cells ex-vivo to understand their unique properties and to further elucidate cellular pathways underlying the self-renewal program of human primary LSC. We established a flow cytometry based high-throughput screen in which we tested more than 6,000 selected compounds with regards to their potential to expand primary human AML cells while preserving their phenotypic and functional characteristics. We considered alteration of surface marker expression, i.e. loss of CD34 and acquisition of markers of myeloid maturation initially not expressed on the cells, as indicator of differentiation implicating at the same time a loss of stem cells in the culture. We hypothesized that compounds that would be able to prevent these alterations in surface marker expression could have the potential to promote self-renewal of primary human LSC ex vivo. A normal-karyotype AML representing the most frequent cytogenetic group of AML in adults with FAB M1 morphology was chosen to perform the screen. Moreover, the initial CD34+CD15- phenotype allowed us to monitor changes in surface marker expression. Cells were plated in 384 well plates with a density of 5,000 cells per well. 6,160 compounds were tested with and without an inhibitor to aryl hydrocarbon receptor (AhR) and the vehicle DMSO was used as negative control resulting in a final DMSO concentration of ∼0.1% in each well, which had been proven to be not toxic to the cells. After 5 days of incubation the cells were analyzed on a BD LSRII high-throughput flow cytometer with regards to CD34 and CD15 surface expression. Compounds showing an increase of ≥45% of CD34+ and CD34+CD15- cells over DMSO compared to the AhR antagonist were selected for further evaluation. In a secondary screen we retested 32 compounds in 5 different concentrations ranging from 1:34 to 3x based on the initial screen concentration after 5 and 9 days of incubation and confirmed an increase ≥50% of relative and absolute CD34+CD15- leukemic cells after 5 days for 13 compounds and after 9 days for 7 compounds. We have initiated functional in-vitro and in-vivo experiments to validate these results and to prove the existence of LSC in cultures where compounds have been added. The ability of the newly identified compounds to preserve human LSC ex-vivo will be further evaluated using a collection of primary AML samples comprising different morphological and cytogenetic groups. Together, our observations document the feasibility of finding anti-differentiation (pro-self-renewal?) compounds of primary human AML cells that can be expanded ex-vivo. These studies represent a first key step in the identification of specific LSC targeting compounds. Disclosures:No relevant conflicts of interest to declare.

Expression of chemokine receptor CX3CR1 characterizes effector and effector memory CD8+ T cells after viral infection (150.4)

Abstract A number of changes in surface marker expression characterize the differentiation of naïve to effector and memory CD8+ T cells. However, no single surface marker has been reported that durably characterizes effector memory (CD62L- and CCR7-) CD8+ T cells and allows distinction from other T cell subsets, in particular central memory CD8+ T cells (CD62L+ CCR7+). We report here the robust surface expression of chemokine receptor CX3CR1 by effector and memory CD8+ T cells following viral challenge. CX3CR1 expression by CD8+ T cells occurred relatively late after activation, appearing on virus specific T cells 4-5 days after LCMV infection. Expression of CD127 increased on CX3CR1hi cells over time and was markedly enriched during the memory phase. Memory CX3CR1hi CD8+ cells did not express central memory associated LN homing molecules CCR7 or CD62L, and failed to enter LNs, while preferentially localizing to peripheral tissues. Memory CX3CR1hi possessed potent cytolytic function while maintaining a modest proliferative capacity following viral rechallenge. These findings characterize CX3CR1 as a robust and distinctly expressed marker to identify long-lived effector memory CD8+ T cell, which to date could only be approximated as cells that express memory markers, but lack lymph node homing receptors. Expression of CX3CR1 by effector memory CD8+ T cells may provide a potent tool for differentially visualizing their in vivo behavior alongside central memory T cells after rechallenge.

Expression of surface markers on the human monocytic leukaemia cell line, THP‐1, as indicators for the sensitizing potential of chemicals

Evaluation of skin sensitization potential is an important part of the safety assessment of cosmetic ingredients and topical drugs. Recently, evaluation of changes in surface marker expression induced in dendritic cells (DC) or DC surrogate cell lines following exposure to chemicals represents one approach for in vitro test methods. The study aimed to test the change of expression patterns of surface markers on THP-1 cells by chemicals as a predictive in vitro method for contact sensitization. We investigated the expression of CD54, CD86, CD83, CD80, and CD40 after a 1-day exposure to sensitizers (1-chloro-2,4-dinitrobenzene; 2,4-dinitrofluorobenzene; benzocaine; 5-chloro-2-methyl-4-isothiazolin-3-one; hexyl cinnamic aldehyde; eugenol; nickel sulfate hexahydrate; potassium dichromate; cobalt sulfate; 2-mercaptobenzothiazole; and ammonium tetrachloroplatinate) and non-sensitizers (sodium lauryl sulfate, benzalkonium chloride, lactic acid, salicylic acid, isopropanol, and dimethyl sulphoxide). The test concentrations were 0.1x, 0.5x, and 1x of the 50% inhibitory concentration, and the relative fluorescence intensity was used as an expression indicator. By evaluating the expression patterns of CD54, CD86, and CD40, we could classify the chemicals as sensitizers or non-sensitizers, but CD80 and CD83 showed non-specific patterns of expression. These data suggest that the THP-1 cells are good model for screening contact sensitizers and CD40 could be a useful marker complementary to CD54 and CD86.

Trehalose 6,6′-dimycolate on the surface of Mycobacterium tuberculosis modulates surface marker expression for antigen presentation and costimulation in murine macrophages

Trehalose 6,6′-dimycolate (TDM) is the most abundant lipid extracted from Mycobacterium tuberculosis (MTB). TDM promotes MTB survival by decreasing phagosomal acidification and phagolysosomal fusion in macrophages. Delipidation of MTB using petroleum ether removes TDM and decreases MTB survival within host cells. TDM reconstituted onto MTB restores its virulent wild-type characteristics. We investigated the role of TDM in regulating surface marker expression in MTB-infected macrophages. Macrophages were infected with wild-type, delipidated, and TDM-reconstituted MTB for 24 h and measured for changes in surface marker expression. TDM on MTB was found to specifically target MHCII, CD1d, CD40, CD80 and CD86. Both wild-type and TDM-reconstituted MTB suppressed or induced no change in expression of these surface markers, whereas delipidated MTB increased expression of the same markers. MTB-infected macrophages were also overlaid with MHCII-restricted T cell hybridomas which recognize Antigen 85B. Macrophages infected by wild-type and TDM-reconstituted MTB did not present antigen as well as delipidated MTB-infected macrophages. The evidence shown furthers supports the notion that TDM present on MTB promotes its survival and persistence in host macrophages.

Dopaminergic regulation of immune cells via D3 dopamine receptor: a pathway mediated by activated T cells.

Neuro-immune interactions enable mutual regulation of the nervous and immune systems. To date, evidence exists for manipulations of immune cells by neurotransmitters in the periphery. In this study, we suggest the existence of a pathway by which the brain affects immune cells. The pathway we describe here is mediated by dopamine receptors expressed on activated T cells, termed blasts. Blasts can cross the blood brain barrier regardless of antigen specificity and can therefore encounter neurotransmitters in the brain. We show that blasts have a unique response to dopaminergic activation, which has no counterpart in resting T cells. Dopaminergic activation of blasts induces a Th1 bias in their cytokine profile and causes changes in surface marker expression. We further suggest that these changes can subsequently be transferred to peripheral T cells. We have tested this pathway in two in vivo systems: in rats exogenously administered with L-dopa, and in schizophrenia, which is characterized by a central nervous system-restricted increase in dopamine. In both models, peripheral T cells exhibit similar features to those of dopaminergically activated blasts. The existence of such a pathway by which the brain can regulate immune cells opens a conceptually new direction in neuro-immune interactions.

T Cell Epitope-Specific Defects in the Immune Response to Cat Allergen in Patients with Atopic Dermatitis

Atopic dermatitis (AD) is often associated with high titer IgE antibodies (ab) to allergens, and IL-10-mediated regulation of IFN-gamma has been proposed to contribute to this IgE ab production. However, the relevance of IL-10 and IFN-gamma to IgE associated with AD has not been examined in the context of an allergen-specific system. Analysis of PBMC responses in vitro showed deficient T cell proliferation to overlapping IL-10- (peptide (P) 2:1) and IFN-gamma- (P2:2) inducing chain 2 major epitopes of cat allergen (Fel d 1) in cultures from sensitized AD patients (mean IgE to cat=20.9 IU/ml). Diminished IFN-gamma induction by Fel d 1 and P2:2, along with elevated peptide-induced IL-10 (except for P2:1) was observed in PBMC cultures from AD subjects compared with non-AD (sensitized and non-sensitized) subjects. Neither T cell proliferation nor IFN-gamma production to chain 2 epitopes could be restored by anti-IL-10 mAb in cultures from sensitized AD subjects. Moreover, allergen avoidance was associated with a paradoxical decrease in both IL-10 and IFN-gamma in peptide-stimulated PBMC from these subjects. Control of IFN-gamma production to chain 2 epitopes by IL-10 may be relevant to sensitization status. Development of high titer IgE ab in AD could reflect a failure of this mechanism.

Elucidating Changes in Surface Marker Expression of Dendritic Cells Following Chemical Allergen Treatment

Dendritic cells (DC) are highly specialized antigen-presenting cells (APC) located in lymphoid and many nonlymphoid tissues, and Langerhans cells (LC), a specialized form of DC, are found in the skin. LC play a critical role in the induction of contact dermatitis and therefore have become a focal point for the development of in vitro cell-based methods for contact sensitization testing. Because of the low abundance of skin-derived LC, methods to culture DC from peripheral blood are being used by investigators to generate LC surrogates to examine the effects of sensitizing chemicals on APC. It has been reported recently that chemical allergens can induce changes in the expression of various DC surface markers and it has been suggested that the measure of these changes in surface marker expression following allergen treatment could provide the basis for an in vitro test method to predict the contact sensitization potential of a chemical. For the work presented here, DC were differentiated from human peripheral blood mononuclear cells (PBMC-DC) in culture medium containing GM–CSF and interleukin (IL)-4 to ensure an immature phenotype or were derived from the KG-1 cell line (KG-1 DC) using a defined cytokine cocktail consisting of GM–CSF, IL-4, Flt-3/Flk-2-ligand, thrombopoietin, stem cell factor, and tumor necrosis factor-α (TNFα). Surface marker expression (HLA-DR, CD54, CD80, and CD86) on these DC was measured by flow cytometry after 48 h treatment with the known chemical allergens dinitrofluorobenzene (DNFB) and methylchloroisothiazolinone/methylisothiazolinone (MCI/MI), the irritant sodium dodecyl sulfate, lipopolysaccharide (LPS), and TNFα. Treatment of PBMC-DC with either MCI/MI or DNFB induced a slight upregulation of class II major histocompatibility (MHC) expression (HLA-DR), whereas LPS and TNFα significantly upregulated CD54 and slightly upregulated CD80 and HLA-DR expression. For KG-1 DC, only MCI/MI upregulated CD86 expression, whereas TNFα upregulated CD54 and slightly upregulated CD80 and CD86 expression. SDS had no effect on surface marker expression in either PBMC-DC or KG-1 DC. Changes in surface marker expression in PBMC-DC treated with chemical allergens were detected in two of five donors, suggesting a limited sensitivity of PBMC-DC under these defined isolation and culture conditions. Furthermore, we found that the presence of GM-CSF and IL-4 during chemical allergen treatment masked the ability to detect changes in surface marker expression. Our data suggest that, under these culture and treatment conditions, measurement of surface marker changes in vitro using PBMC-DC or KG-1 DC does not provide a sensitive in vitro method with sufficient dynamic range for assessing the contact sensitization potential of a chemical.

Surface activation markers of T lymphocytes: role in the detection of infection in neonates.

Diagnosis of perinatal infection in the newborn is difficult; there may be few clinical signs and current tests are slow or non-specific. Detection of organisms, antigen or specific antibody to common pathogens often requires repeat samples and does not give immediate results. Haematological parameters, although relied upon frequently to diagnose infection in the neonate prior to a positive bacterial isolation, are unreliable and insensitive. Indicators such as an increase in neutrophil band cell counts are highly variable between morphologists. Infection induces the expression of a number of T lymphocyte surface markers, including CD45RA/CD45RO and CD45RO. The use of changed expression of surface markers as a laboratory test for detection of infection in neonates was evaluated. We used multiparameter flow cytometry to detect expression of early (CD45RA/CD45RO) and late (CD45RO) activation markers. In the respective groups of 50 full term (including 25 normal vaginal deliveries and 25 caesarean deliveries) and 30 premature, i.e. < 36 weeks gestation (born by either normal vaginal delivery or caesarean delivery) the CD45RA isoform was brightly expressed on newborn 'naive' CD4+ T cells, whereas the CD45RO isoform (including both 'bright' and 'dim' populations) was present on < 19% of CD4+ T cells from these newborn infants. In a group of 37 infants, tested to evaluate possible effects of non-infective parameters such as respiratory distress and iso-immunization, no significant changes in surface marker expression were found and specificity of the test was confirmed. In 14 neonates with documented sepsis, up-regulation of dual staining CD45RA/CD45RO isoforms on CD4+ T cells was detected early in the infection. In addition, we found that CD45RO expression persisted for several weeks after bacterial infection, and up to several months in viral infection. In conclusion, detection of T cell activation by flow cytometry for the early diagnosis of neonatal infection is an easy test to carry out on small volumes of blood, is inexpensive, and may be a specific indicator of infection.