Epigenetic dysregulation of ACE2 and interferon-regulated genes might suggest increased COVID-19 susceptibility and severity in lupus patients.

Infection caused by SARS-CoV-2 can result in severe respiratory complications and death. Patients with a compromised immune system are expected to be more susceptible to a severe disease course. In this report we suggest that patients with systemic lupus erythematous might be especially prone to severe COVID-19 independent of their immunosuppressed state from lupus treatment. Specifically, we provide evidence in lupus to suggest hypomethylation and overexpression of ACE2, which is located on the X chromosome and encodes a functional receptor for the SARS-CoV-2 spike glycoprotein. Oxidative stress induced by viral infections exacerbates the DNA methylation defect in lupus, possibly resulting in further ACE2 hypomethylation and enhanced viremia. In addition, demethylation of interferon-regulated genes, NFκB, and key cytokine genes in lupus patients might exacerbate the immune response to SARS-CoV-2 and increase the likelihood of cytokine storm. These arguments suggest that inherent epigenetic dysregulation in lupus might facilitate viral entry, viremia, and an excessive immune response to SARS-CoV-2. Further, maintaining disease remission in lupus patients is critical to prevent a vicious cycle of demethylation and increased oxidative stress, which will exacerbate susceptibility to SARS-CoV-2 infection during the current pandemic. Epigenetic control of the ACE2 gene might be a target for prevention and therapy in COVID-19.

The down-regulation of hsa_circ_0012919, the sponge for miR-125a-3p, contributes to DNA methylation of CD11a and CD70 in CD4+ T cells of systemic lupus erythematous.

BACKGROUND: Systemic lupus erythematous (SLE) is an autoimmune disease characterized by the production of autoantibodies directed against various autoantigens. But the expression profiles and functions of circular RNAs (circRNAs) in SLE are still scarce. OBJECTIVES: To explore the roles of circRNA in SLE and its potential diagnostic potential in SLE. METHODS: SLE patients and healthy control subjects were recruited. CD4+ T cells were isolated, circRNA microarray analysis were used to screen for circRNA candidate in CD4+ T cells. Expression of DNMT1, CD11a and CD70, and methylation level of CD11a and CD70 were detected after transfecting hsa_circ_0012919-targetted siRNA. The network analysis of hsa_circ_0012919 was used by bioinformatics. Luciferase reporter assay and fluorescence in situ hybridization (FISH) assay were used for screening for which miRNAs could bind with hsa_circ_0012919. RESULTS: Twelve circRNAs were up-regulated and two circRNAs were down-regulated in SLE patients group after circRNA microarray analysis. Hsa_circ_0012919 was further confirmed to be significantly different between healthy control and SLE patients (P<0.05) and associated with SLE characters (P<0.05). Down-regulation of hsa_circ_0012919 (i) increased the expression of DNMT1 and reduced the expression of CD70, CD11a, (ii) reversed the DNA hypomethylation of CD11a and CD70 in CD4+ T cells of SLE, but it could be reversed by down-regulation of DNMT1. Hsa_circ_0012919 regulated KLF13 and RANTES by miR-125a Conclusion: Hsa_circ_0012919 could be regarded as a biomarker for SLE and hsa_circ_0012919 was the competitive endogenous RNA (ceRNA) for miR-125a-3p.

Identification of Stage-Specific Surface Markers in Early B Cell Development Provides Novel Tools for Identification of Progenitor Populations.

Whereas the characterization of B lymphoid progenitors has been facilitated by the identification of lineage- and stage-specific surface markers, the continued identification of differentially expressed proteins increases our capacity to explore normal and malignant B cell development. To identify novel surface markers with stage-specific expression patterns, we explored the reactivity of CD19(+) B cell progenitor cells to Abs targeted to 176 surface proteins. Markers with stage-specific expression were identified using a transgenic reporter gene system subdividing the B cell progenitors into four surface IgM(-) stages. This approach affirmed the utility of known stage-specific markers, as well as identifying additional proteins that selectively marked defined stages of B cell development. Among the stage-specific markers were the cell adhesion proteins CD49E, CD11A, and CD54 that are highly expressed selectively on the most immature progenitors. This work identifies a set of novel stage-specific surface markers that can be used as a complement to the classical staining protocols to explore B lymphocyte development.

Transient Surface CCR5 Expression by Naive CD8+ T Cells within Inflamed Lymph Nodes Is Dependent on High Endothelial Venule Interaction and Augments Th Cell-Dependent Memory Response.

In inflamed lymph nodes, Ag-specific CD4(+) and CD8(+) T cells encounter Ag-bearing dendritic cells and, together, this complex enhances the release of CCL3 and CCL4, which facilitate additional interaction with naive CD8(+) T cells. Although blocking CCL3 and CCL4 has no effect on primary CD8(+) T cell responses, it dramatically impairs the development of memory CD8(+) T cells upon Ag rechallenge. Despite the absence of detectable surface CCR5 expression on circulating native CD8(+) T cells, these data imply that naive CD8(+) T cells are capable of expressing surface CCR5 prior to cognate Ag-induced TCR signaling in inflamed lymph nodes; however, the molecular mechanisms have not been characterized to date. In this study, we show that CCR5, the receptor for CCL3 and CCL4, can be transiently upregulated on a subset of naive CD8(+) T cells and that this upregulation is dependent on direct contact with the high endothelial venule in inflamed lymph node. Binding of CD62L and CD11a on T cells to their ligands CD34 and CD54 on the high endothelial venule can be enhanced during inflammation. This enhanced binding and subsequent signaling promote the translocation of CCR5 molecules from intracellular vesicles to the surface of the CD8(+) T cell. The upregulation of CCR5 on the surface of the CD8(+) T cells increases the number of contacts with Ag-bearing dendritic cells, which ultimately results in increased CD8(+) T cell response to Ag rechallenge.

CD11a/ICAM-1 blockade combined with IL-2 targeting therapy causes a paradoxical acceleration of type 1 diabetes.

Enhancement of regulatory T-cell (Treg) function is the goal of many immunotherapies aimed at treating type 1 diabetes (T1D). The use of interleukin (IL)-2 is hindered by its effects on other populations such as effector T cells and NK cells. Combination therapies aimed at suppressing effector T cells while using IL-2 to expand Tregs could be beneficial and have been trialed in T1D patients. We have investigated a combination therapy using IL-2 and αCD11a blocking antibody to simultaneously expand Tregs and suppress the activation and migration of autoreactive T cells. When non-obese diabetic mice were treated with low-dose IL-2/anti-IL-2 complexes (IL-2c) and αCD11a, significant Treg expansion occurred in both the spleen and pancreas. Activation and IFNγ production by islet-specific T cells was robustly suppressed in the periphery following IL-2c/αCD11a treatment. Surprisingly, combination therapy accelerated diabetes onset compared with control treatments. Analysis of IL-2 responsive populations found that combination therapy increased the activation of CD8+ T cells and natural killer (NK) cells specifically within the pancreas despite concomitant Treg expansion. Blocking effector T-cell migration with the inhibitor FTY720 together with IL-2c treatment also resulted in intra-pancreatic expansion of effector cell populations. Thus, inhibiting effector T-cell migration into the islets unleashes islet-resident pathogenic effectors in the presence of low doses of exogenous IL-2.

IL-18 Is Involved in Eosinophil-Mediated Tumoricidal Activity against a Colon Carcinoma Cell Line by Upregulating LFA-1 and ICAM-1.

Eosinophils are multifunctional leukocytes that are involved in innate and adaptive immune responses through the expression of various receptors and mediators. Previously, we showed that human eosinophils and T cells shared cytotoxic activities against tumor cells that involved the γ-δ TCR and cell-cell contact. In this study, we investigated the molecules involved in eosinophil-tumor cell interactions. Given the role of IL-18 in cell adhesion and in protecting against colon cancer, we evaluated its role in eosinophil-mediated cytotoxicity against Colo-205, a human colon carcinoma cell line. We found that human eosinophils exerted dose- and time-dependent tumoricidal activity against Colo-205 cells. Neutralization of IL-18 significantly reduced eosinophil-mediated Colo-205 apoptosis and inhibited cell-cell adhesion. Moreover, addition of rIL-18 led to upregulation of CD11a and ICAM-1 adhesion molecules, which were involved in the contact between eosinophils and Colo-205 cells. Our results indicated that IL-18 was involved in the eosinophil-mediated death of Colo-205 by facilitating contact between effector and target cells. These data underscored the involvement of an additional mediator in eosinophil-mediated antitumor cytotoxicity. Our findings support existing evidence that eosinophils could play a beneficial role in the context of colon cancer.

Targeted Delivery of LXR Agonist Using a Site-Specific Antibody-Drug Conjugate.

Liver X receptor (LXR) agonists have been explored as potential treatments for atherosclerosis and other diseases based on their ability to induce reverse cholesterol transport and suppress inflammation. However, this therapeutic potential has been hindered by on-target adverse effects in the liver mediated by excessive lipogenesis. Herein, we report a novel site-specific antibody-drug conjugate (ADC) that selectively delivers a LXR agonist to monocytes/macrophages while sparing hepatocytes. The unnatural amino acid para-acetylphenylalanine (pAcF) was site-specifically incorporated into anti-CD11a IgG, which binds the α-chain component of the lymphocyte function-associated antigen 1 (LFA-1) expressed on nearly all monocytes and macrophages. An aminooxy-modified LXR agonist was conjugated to anti-CD11a IgG through a stable, cathepsin B cleavable oxime linkage to afford a chemically defined ADC. The anti-CD11a IgG-LXR agonist ADC induced LXR activation specifically in human THP-1 monocyte/macrophage cells in vitro (EC50-27 nM), but had no significant effect in hepatocytes, indicating that payload delivery is CD11a-mediated. Moreover, the ADC exhibited higher-fold activation compared to a conventional synthetic LXR agonist T0901317 (Tularik) (3-fold). This novel ADC represents a fundamentally different strategy that uses tissue targeting to overcome the limitations of LXR agonists for potential use in treating atherosclerosis.

Natalizumab treatment alters the expression of T-cell trafficking marker LFA-1 α-chain (CD11a) in MS patients.

OBJECTIVE: To determine the long-term effect of natalizumab (NTZ) treatment on the expression of integrins and chemokine receptors involved in the migration of T cells towards the central nervous system (CNS). METHODS: We drew the blood of 23 patients just before starting NTZ therapy and every 12 months thereafter, for up to 48 months of treatment. We assessed the ex-vivo expression of phenotype markers (CCR7 and CD45RA), CNS-addressing integrins (CD11a, CD49d and CD29) and chemokine receptors (CXCR3 and CCR6) in CD4+ or CD8+ T-cell subsets by flow cytometry. RESULTS: As compared to the pre-NTZ values, there was a marked increase in central memory (CCR7+/CD45RA-) CD4+ T cells and in effector memory (CCR7-/CD45RA-) CD8+ T cells at 12 and 24 months. In addition to an expected downregulation of both VLA-4 subunits (CD49d/CD29), we also found decreased T-cell expression of CXCR3 at 12 months, and of CD11a (LFA-1 αL subunit) at 12 months, but mostly at 24 months of NTZ treatment. CONCLUSION: Our data show a nadir of CD11a expression at 2 years of NTZ treatment, at the peak of incidence of progressive multifocal leukoencephalopathy (PML), indirectly suggesting that a lack of these molecules may play a role in the onset of PML in NTZ-treated patients.

Immunomodulatory action of dietary fish oil and targeted deletion of intestinal epithelial cell PPARδ in inflammation-induced colon carcinogenesis.

The ligand-activated transcription factor peroxisome proliferator-activated receptor (PPAR)-δ is highly expressed in colonic epithelial cells; however, the role of PPARδ ligands, such as fatty acids, in mucosal inflammation and malignant transformation has not been clarified. Recent evidence suggests that the anti-inflammatory/chemoprotective properties of fish oil (FO)-derived n-3 polyunsaturated fatty acids (PUFAs) may be partly mediated by PPARδ. Therefore, we assessed the role of PPARδ in modulating the effects of dietary n-3 PUFAs by targeted deletion of intestinal epithelial cell PPARδ (PPARδ(ΔIEpC)). Subsequently, we documented changes in colon tumorigenesis and the inflammatory microenvironment, i.e., local [mesenteric lymph node (MLN)] and systemic (spleen) T cell activation. Animals were fed chemopromotive [corn oil (CO)] or chemoprotective (FO) diets during the induction of chronic inflammation/carcinogenesis. Tumor incidence was similar in control and PPARδ(ΔIEpC) mice. FO reduced mucosal injury, tumor incidence, colonic STAT3 activation, and inflammatory cytokine gene expression, independent of PPARδ genotype. CD8(+) T cell recruitment into MLNs was suppressed in PPARδ(ΔIEpC) mice. Similarly, FO reduced CD8(+) T cell numbers in the MLN. Dietary FO independently modulated MLN CD4(+) T cell activation status by decreasing CD44 expression. CD11a expression by MLN CD4(+) T cells was downregulated in PPARδ(ΔIEpC) mice. Lastly, splenic CD62L expression was downregulated in PPARδ(ΔIEpC) CD4(+) and CD8(+) T cells. These data demonstrate that expression of intestinal epithelial cell PPARδ does not influence azoxymethane/dextran sodium sulfate-induced colon tumor incidence. Moreover, we provide new evidence that dietary n-3 PUFAs attenuate intestinal inflammation in an intestinal epithelial cell PPARδ-independent manner.

Human eosinophils exert TNF-α and granzyme A-mediated tumoricidal activity toward colon carcinoma cells.

Peripheral blood and tissue eosinophilia is a prominent feature in allergic diseases and helminth infections. In cancer patients, tumor-associated tissue eosinophilia is frequently observed. Tumor-associated tissue eosinophilia can be associated with a favorable prognosis, notably in colorectal carcinoma. However, underlying mechanisms of eosinophil contribution to antitumor responses are poorly understood. We have in this study investigated the direct interactions of human eosinophils with Colo-205, a colorectal carcinoma cell line, and show that eosinophils induce apoptosis and directly kill tumor cells. Using blocking Abs, we found that CD11a/CD18 complex is involved in the tumoricidal activity. Coculture of eosinophils with Colo-205 led to the release of eosinophil cationic protein and eosinophil-derived neurotoxin as well as TNF-α secretion. Moreover, eosinophils expressed granzyme A, which was released upon interaction with Colo-205, whereas cytotoxicity was partially inhibited by FUT-175, an inhibitor of trypsin-like enzymatic activity. Our data present the first demonstration, to our knowledge, that granzyme A is a cytotoxic mediator of the eosinophil protein arsenal, exerting eosinophil tumoricidal activity toward Colo-205, and provide mechanistic evidence for innate responses of eosinophil against tumor cells.

NK cells promote islet allograft tolerance via a perforin-dependent mechanism.

Although major histocompatibility complex (MHC) class II-restricted CD4 T cells are well appreciated for their contribution to peripheral tolerance to tissue allografts, little is known regarding MHC class I-dependent reactivity in this process. Here we show a crucial role for host MHC class I-dependent NK cell reactivity for allograft tolerance in mice induced through either costimulation blockade using CD154-specific antibody therapy or by targeting LFA-1 (also known as CD11a). Tolerance induction absolutely required host expression of MHC class I, but was independent of CD8 T cell-dependent immunity. Rather, tolerance required innate immunity involving NK1.1(+) cells, but was independent of CD1d-restricted NKT cells. Therefore, NK cells seem to be generally required for induction of tolerance to islet allografts. Additional studies indicate that CD154-specific antibody-induced allograft tolerance is perforin dependent. Notably, NK cells that are perforin competent are sufficient to restore allograft tolerance in perforin-deficient recipients. Together, these results show an obligatory role for NK cells, through perforin, for induction of tolerance to islet allografts.

Costimulatory signals potently modulate the T cell inhibitory capacity of the therapeutic CD11a antibody Efalizumab.

The therapeutic CD11a antibody Efalizumab interferes with psoriasis pathogenesis by blocking T cell activation and migration. We have performed a detailed analysis on its effects during the activation of human T cells and found that the capability of Efalizumab to inhibit proliferation and cytokine production of T cells critically depends on the quality and quantity of costimulatory signals. Efalizumab potently inhibited the proliferation and cytokine production of human T cells costimulated via ICOS, OX40, CD27 or 4-1BB, but did not significantly inhibit T cells that received stimuli via CD2 or CD28. The capacity of CD2 and CD28 signals to interfere with the T cell inhibitory effects of Efalizumab was also observed upon stimulation of T cells with allogeneic DC. Furthermore, studies with T cells from psoriasis patients indicated that Efalizumab therapy induces inhibition of T cell responses that can be reverted by CD2 or CD28 signals.

Effects of CD70 and CD11a in immune thrombocytopenia patients.

INTRODUCTION: CD70 and CD11a are co-stimulatory molecules that are important for the immune functions of T, B lymphocytes. Over-expressions of CD70 or CD11a cause T cell to be autoreactive. OBJECTIVES: The purpose of this study was to explore the effect of CD70 and CD11a in immune thrombocytopenia (ITP). METHODS: CD70 and CD11a mRNAs and protein expressions in CD4(+) T cells from ITP patients were measured respectively by real-time quantitative-PCR (RT-PCR) and flow cytometry. The apoptosis of T cells, B cells, and platelets in the PBMCs were analyzed by flow cytometry, and secretion of IL-4, IFN-γ, as well as IgG in the reaction supernatant were detected by ELISA. In order to investigate the effects of CD70 and CD11a over-expression on pathogenesis of ITP, anti-CD70, and anti-CD11a mAbs were used to block the signaling pathways. RESULTS: CD70 and CD11a mRNAs and protein expressions in CD4(+) T cells from ITP patients were significantly higher than healthy controls. In vitro co-culturing of PBMCs with anti-CD70 or anti-CD11a, the apoptosis of T, B lymphocytes were significantly increased but apoptosis of platelets were reduced. Anti-CD11a and anti-CD70 both significantly suppressed the secretion of IFN-γ, while anti-CD11a significantly promoted the secretion of IL-4. There was no significant difference in the healthy group. CONCLUSIONS: CD70 and CD11a facilitate the survival of T, B lymphocytes and indirectly enhance the destruction of platelets in ITP. Blockade of CD70 or CD11a are promising therapeutic approaches for ITP.

Dendritic cells adhere to and transmigrate across lymphatic endothelium in response to IFN-α.

Migration of DC into lymphatic vessels ferries antigenic cargo and pro-inflammatory stimuli into the draining LN. Given that tissues under the influence of viral infections produce type I IFN, it is conceivable that these cytokines enhance DC migration in order to facilitate an antiviral immune response. Cultured lymphatic endothelium monolayers pretreated with TNF-α were used to model this phenomenon under inflammatory conditions. DC differentiated in the presence of either IFN-α2b or IFN-α5 showed enhanced adhesion to cultured lymphatic endothelial cells. These pro-adhesive effects were mediated by DC, not the lymphatic endothelium, and correlated with increased DC transmigration across lymphatic endothelial cell monolayers. Transmigration was guided by chemokines acting on DC, and blocking experiments with mAb indicated a role for LFA-1. Furthermore, incubation of DC with IFN-α led to the appearance of active conformation epitopes on the CD11a integrin chains expressed by DC. Differentiation of mouse DC in the presence of IFN-α also increased DC migration from inflammed footpads toward popliteal LN. Collectively, these results indicate a role for type I IFN in directing DC toward LN under inflammatory conditions.

Wiskott-Aldrich syndrome protein is required for homeostasis and function of invariant NKT cells.

NKT cells comprise a separate T lineage expressing semi-invariant T cell receptors. Canonical invariant NKT (iNKT) cells specifically recognize lipid Ags presented by CD1d, a MHC class I-like molecule. iNKT cells function, in part, as initial responders to bacterial infection and play a role in immune surveillance and tumor rejection. The Wiskott-Aldrich Syndrome protein (WASp) serves as a crucial link between cellular stimuli and cytoskeletal rearrangements. Although we and others have identified a key role for WASp in homeostasis of T-regulatory and marginal zone B cells, little data exist regarding the role for WASp within the iNKT lineage. Analysis of WASp-expressing cell populations in heterozygous female WASp mice revealed a substantial selective advantage for WASp(+) vs WASp(-) iNKT cells. Although adult WASp-deficient (WASp(-/-)) mice had normal thymic and bone marrow iNKT numbers, we observed 2- to 3-fold reduction in the numbers of iNKT cells in the spleen and liver. This peripheral iNKT deficit is manifested, in part, due to defective iNKT homeostasis. WASp(-/-) iNKT cells exhibited reduced levels of integrin surface expression and decreased homing and/or retention within peripheral tissues in a competitive repopulation model. In addition, analysis of young mice showed that WASp is important for both maturation and egress of thymic iNKT cells. WASp(-/-) iNKT cells also exhibited a marked reduction in Ag-induced proliferation and cytokine production. Our findings highlight the crucial role for WASp in iNKT development, homeostasis, and activation, and identify iNKT dysfunction as an additional factor likely to contribute to the clinical features observed in WAS patients.

Increased expression of CD11a and CD45 on leukocytes and decreased serum TNF-alpha levels in patients with isolated coronary artery ectasia.

BACKGROUND: Aneurysm and ectasia have similar pathological pathways. TH2-associated cytokines are stimulated by aneurismal tissue and correspondingly lack mediators associated with TH1 response. In this study, we measured serum TNF-alpha and IL-18 levels which are strong TH1 stimulating cytokines and also investigated the expression of CD11a, CD11b, CD18 adhesion molecules and CD45 on leukocytes in patients with coronary artery ectasia (CAE) and controls with normal coronary arteries (NCA). METHODS: A total of 51 isolated CAE patients free of atherosclerosis and 37 NCA controls were included in the study. Cell counts and cell surface adhesion molecules were detected by flow cytometry using fluorescence conjugated monoclonal antibodies. Serum TNF-alpha, IL-18 levels, and Chlamydophila pneumoniae IgG and IgM and Helicobacter pylori IgG levels were detected by ELISA methods. RESULTS: The mean fluorescence intensities of CD11a on granulocytes, monocytes and lymphocytes and CD45 on granulocytes and monocytes were significantly higher in CAE patients when compared with the NCA group (10.01 +/- 8.2 vs. 6.79 +/- 3.49, p = 0.04; 15.84 +/- 8.64 vs. 11.56 +/- 5.27, p = 0.016; 29.58 +/- 9.98 vs. 20.02 +/- 9.66, p < 0.001; 7.58 +/- 5.03 vs. 4.57 +/- 3.05, p = 0.003; 18.73 +/- 1238 vs. 10.74 +/- 738, p = 0.004; respectively) detected by flow cytometry. TNF-alpha levels were significantly lower in the patient group (18.76 +/- 7.07 vs. 24.29 +/- 8.46; p < 0.001) when compared with controls. The percentage of granulocytes was higher in the CAE group when compared with the NCA group (65.52 +/- 14.91 vs. 52.28 +/- 1537; p = 0.002). Contrarily, the percentage of monocytes was higher in the control group when compared with the CAE group (18.12 +/- 15.69 vs. 934 +/- 733 p = 0.008). Among the infection markers studied, only C. pneumoniae IgG levels were significantly higher in patients when compared with controls (81.62 +/- 48.53 RU/mL vs. 63.79 +/- 33.83 RU/mL; p = 0.045). In CAE patients, TNF-alpha levels significantly correlated with mean fluorescence intensity levels of CD45+ granulocyte (0.525, p < 0.001), monocyte (0.469, p = 0.001) and lymphocytes (0376, p = 0.013). CONCLUSIONS: The decreased levels of TNF-alpha may indicate predominance of TH2 and lack of TH1 type immunity in CAE patients, similar to patients with aortic aneurysms. Increased levels of cell surface adhesion molecules in CAE are an indicator of activation of leukocytes for adherence and transmigration through the vessels for the initiation of inflammation.

NK cells from tuberculous pleurisy express high ICAM-1 levels and exert stimulatory effect on local T cells.

Tuberculous pleurisy, one of the most common manifestations of extrapulmonary tuberculosis, is characterized by a T-cell-mediated hypersensitivity reaction along with a Th1 immune profile. In this study, we investigated functional cross-talk among T and NK cells in human tuberculous pleurisy. We found that endogenously activated pleural fluid-derived NK cells express high ICAM-1 levels and induce T-cell activation ex vivo through ICAM-1. Besides, upon in vitro stimulation with monokines and PAMP, resting peripheral blood NK cells increased ICAM-1 expression leading to cellular activation and Th1 polarization of autologous T cells. Furthermore, these effects were abolished by anti-ICAM-1 Ab. Hence, NK cells may contribute to the adaptive immune response by a direct cell-contact-dependent mechanism in the context of Mycobacterium tuberculosis infection.

Investigating the role of proinflammatory CD16+ monocytes in the pathogenesis of inflammatory bowel disease.

Infiltrating monocytes and macrophages contribute to the initiation and perpetuation of mucosal inflammation characteristic for human inflammatory bowel disease (IBD). Peripheral blood monocytes expressing the low-affinity Fcgamma receptor CD16 have been identified previously as a major proinflammatory cell population, based on their unique cytokine secretion profile. However, the contribution of these cells to the pathogenesis of inflammatory bowel disease remains to be elucidated. Thus, in this study we investigated whether the peripheral CD16(+) monocyte count correlates with common IBD disease parameters, and whether these cells infiltrate the intestinal mucosa under inflammatory conditions. We observed that CD16(+) peripheral blood monocytes are increased significantly in active Crohn's disease, particularly in patients with high Crohn's disease activity index and colonic involvement. Furthermore, we found that CD16(+) cells are a major contributor to the inflammatory infiltrate in Crohn's disease mucosa, although their spontaneous migration through primary human intestinal endothelial cells is limited. Our data suggest that lamina propria, but not peripheral blood, CD16(+) monocytes are a crucial proinflammatory cell population in IBD, and a potential target for anti-inflammatory therapy.

Phenotypic characterization of gammadelta T cells mobilized in response to acute psychological stress.

Gamma-delta (gammadelta) T lymphocytes are versatile cells that play key roles in bacterial clearance, wound repair, and delayed-type hypersensitivity reactions. Recently we showed that these cells are mobilized into the blood during acute psychological stress. gammadelta T lymphocytes are a heterogeneous population of cells, and the current study aimed to characterize the effects of stress on distinct gammadelta T cell populations. Twenty-nine healthy participants completed a 12min speech task. Blood samples were taken after a resting baseline, during the last two minutes of the task, and after a 15min recovery period. Flow cytometry was used to investigate the response of memory phenotypes (i.e. Naïve, Central memory, Effector Memory, and CD45RA(+) Effector Memory (EMRA)) within the delta1 and delta2 gammadelta T cell populations. Cells were further analysed on expression of adhesion molecules (CD11a, CD62L) and the NK-receptor CD94. Both the delta1 and delta2 subsets were mobilized during stress, and for both subsets, EMRA cells were mobilized to a much greater extent than the other memory phenotypes. Analysis of migration markers revealed that mobilized cells had a predominantly tissue migrating phenotype (CD11a(hi)CD62L(lo/neg)) and expressed high levels of the NK-receptor CD94. The current findings indicate that stress primarily mobilizes gammadelta memory cells that have high cytotoxic capability, tissue homing potential, and the capacity for rapid, innate-like target recognition. This selective mobilization possibly provides protection in contexts when tissue damage and antigen exposure are more likely to occur.