Background

Interleukin-1 receptor associated kinase-4 (IRAK-4) is an effector of the Toll-like receptor and interleukin-1 receptor pathways, which plays a critical role in innate immune responses. The role of IRAK-4 in adaptive immune functions in humans is incompletely understood.

Objective

To evaluate T cell function in Interleukin-1 receptor associated kinase-4 deficient patients.

Methods

We compared upregulation of CD25 and CD69 on T cells, and production of interleukin-2, interleukin-6, and interferon gamma following stimulation of peripheral blood mononuclear cells from four IRAK-4 deficient patients and normal controls with anti-CD3 and anti-CD28.

Results

Upregulation of CD25 and CD69 on T cells and production of interleukin-6 and interferon-gamma, but not interleukin-2, was significantly reduced in IRAK-4 deficient patients.

Conclusions

IRAK-4 deficient patients have defects in T cell activation.

Clinical Implications

Defects in T cell activation may contribute to the susceptibility of IRAK-4 deficient patients to infections.

Vascular perturbation is a hallmark of severe forms of dengue disease. We show here that antibody-enhanced dengue virus infection of primary human cord blood-derived mast cells (CBMCs) and the human mast cell-like line HMC-1 results in the release of factor(s) which activate human endothelial cells, as evidenced by increased expression of the adhesion molecules ICAM-1 and VCAM-1. Endothelial cell activation was prevented by pretreatment of mast cell-derived supernatants with a tumor necrosis factor (TNF)-specific blocking antibody, thus identifying TNF as the endothelial cell-activating factor. Our findings suggest that mast cells may represent an important source of TNF, promoting vascular endothelial perturbation following antibody-enhanced dengue virus infection.

Although platelets induce lung inflammation, leading to acute lung injury (ALI), the extent of platelet–endothelial cell (EC) interactions remains poorly understood. Here, in a ventilation-stress model of lung inflammation, we show that platelet–EC interactions are important. We obtained freshly isolated lung endothelial cells (FLECs) from isolated, blood-perfused rat lungs exposed to ventilation at low tidal volume (LV) or stress-inducing high tidal volume (HV). Immunofluorescence and immunoprecipitation studies revealed HV-induced increases in cell-surface von Willebrand factor (vWf) expression on FLEC. This increased expression was inhibited by platelet removal from the lung perfusion and by including a P-selectin–blocking antibody in the lung perfusion. The expression was also blocked in lungs from P-selectin knockout (P sel−/−) mice perfused with autologous blood, but not with heterologous wild-type blood containing P-selectin–expressing platelets. These findings indicate that in ventilation stress, platelets transfer vWf to the EC surface and that platelet P-selectin plays a critical role in this transfer. Further evidence for such intercellular transfers was the HV-induced FLEC expressions of platelet glycoprotein 1b and of platelet P-selectin. We conclude that in ventilation stress, platelets deposit leukocyte- and platelet-binding proteins on the EC surface, thereby establishing the proinflammatory phenotype of the vascular lining.

Human interleukin (IL) 1 receptor–associated kinase 4 (IRAK-4) deficiency is a recently discovered primary immunodeficiency that impairs Toll/IL-1R immunity, except for the Toll-like receptor (TLR) 3– and TLR4–interferon (IFN)-a/b pathways. The clinical and immunological phenotype remains largely unknown. We diagnosed up to 28 patients with IRAK-4 deficiency, tested blood TLR responses for individual leukocyte subsets, and TLR responses for multiple cytokines. The patients' peripheral blood mononuclear cells (PBMCs) did not induce the 11 non-IFN cytokines tested upon activation with TLR agonists other than the nonspecific TLR3 agonist poly(I:C). The patients' individual cell subsets from both myeloid (granulocytes, monocytes, monocyte-derived dendritic cells [MDDCs], myeloid DCs [MDCs], and plasmacytoid DCs) and lymphoid (B, T, and NK cells) lineages did not respond to the TLR agonists that stimulated control cells, with the exception of residual responses to poly(I:C) and lipopolysaccharide in MDCs and MDDCs. Most patients (22 out of 28; 79%) suffered from invasive pneumococcal disease, which was often recurrent (13 out of 22; 59%). Other infections were rare, with the exception of severe staphylococcal disease (9 out of 28; 32%). Almost half of the patients died (12 out of 28; 43%). No death and no invasive infection occurred in patients older than 8 and 14 yr, respectively. The IRAK-4–dependent TLRs and IL-1Rs are therefore vital for childhood immunity to pyogenic bacteria, particularly Streptococcus pneumoniae. Conversely, IRAK-4–dependent human TLRs appear to play a redundant role in protective immunity to most infections, at most limited to childhood immunity to some pyogenic bacteria.

Although high tidal volume ventilation exacerbates lung injury, the mechanisms underlying the inflammatory response are not clear. Here, we exposed isolated lungs to high or low tidal volume ventilation, while perfusing lungs with whole blood, or blood depleted of leukocytes and platelets. Then, we determined signaling responses in freshly isolated lung endothelial cells by means of immunoblotting and immunofluorescence approaches. In depleted blood perfusion, high tidal volume induced modest increases in both P-selectin expression on the endothelial surface, and in endothelial protein tyrosine phosphorylation. Both high tidal volume–induced responses were markedly enhanced in the presence of whole blood perfusion. However, a P-selectin–blocking antibody given together with whole blood perfusion inhibited the responses down to levels corresponding to those for depleted blood perfusion. These findings indicate that the full proinflammatory response occurs in two stages. First, lung distension causes modest endothelial activation. Second, subsequent endothelial–inflammatory cell interactions augment P-selectin expression and tyrosine phosphorylation. We conclude that interactions of circulating inflammatory cells with P-selectin critically determine proinflammatory endothelial activation during high tidal volume ventilation.

Attempts to repair muscle damage in Duchenne muscular dystrophy (DMD) by transplanting skeletal myoblasts directly into muscles are faced with the problem of the limited migration of these cells in the muscles. The delivery of myogenic stem cells to the sites of muscle lesions via the systemic circulation is a potential alternative approach to treat this disease. Muscle-derived stem cells (MDSCs) were obtained by a MACS® multisort method. Clones of MDSCs, which were Sca-1+/CD34−/L-selectin+, were found to adhere firmly to the endothelium of mdx dystrophic muscles after i.v. or i.m. injections. The subpopulation of Sca-1+/CD34− MDSCs expressing L-selectin was called homing MDSCs (HMDSCs). Treatment of HMDSCs with antibodies against L-selectin prevented adhesion to the muscle endothelium. Importantly, we found that vascular endothelium from striate muscle of young mdx mice expresses mucosal addressin cell adhesion molecule-1 (MAdCAM-1), a ligand for L-selectin. Our results showed for the first time that the expression of the adhesion molecule L-selectin is important for muscle homing of MDSCs. This discovery will aid in the improvement of a potential therapy for muscular dystrophy based on the systemic delivery of MDSCs.

Although capillary barrier deterioration underlies major inflammatory lung pathology, barrier-enhancing strategies are not available. To consider hyperosmolar therapy as a possible strategy, we gave 15-minute infusions of hyperosmolar sucrose in lung venular capillaries imaged in real time. Surprisingly, this treatment enhanced the capillary barrier, as indicated by quantification of the capillary hydraulic conductivity. The barrier enhancement was sufficient to block the injurious effects of thrombin, TNF-α, and H2O2 in single capillaries, and of intratracheal acid instillation in the whole lung. Capillary immunofluorescence indicated that the hyperosmolar infusion markedly augmented actin filament formation and E-cadherin expression at the endothelial cell periphery. The actin-depolymerizing agent latrunculin B abrogated the hyperosmolar barrier enhancement as well as the actin filament formation, suggesting a role for actin in the barrier response. Furthermore, hyperosmolar infusion blocked TNF-α–induced P-selectin expression in an actin-dependent manner. Our results provide the first evidence to our knowledge that in lung capillaries, hyperosmolarity remodels the endothelial barrier and the actin cytoskeleton to enhance barrier properties and block proinflammatory secretory processes. Hyperosmolar therapy may be beneficial in lung inflammatory disease.

Elevation of lung capillary pressure causes exocytosis of the leukocyte adhesion receptor P-selectin in endothelial cells (ECs), indicating that lung ECs generate a proinflammatory response to pressure-induced stress. To define underlying mechanisms, we followed the EC signaling sequence leading to P-selectin exocytosis through application of real-time, in situ fluorescence microscopy in lung capillaries. Pressure elevation increased the amplitude of cytosolic Ca2+ oscillations that triggered increases in the amplitude of mitochondrial Ca2+ oscillations and in reactive oxygen species (ROS) production. Responses to blockers of the Ca2+ oscillations and of mitochondrial electron transport indicated that the ROS production was Ca2+ dependent and of mitochondrial origin. A new proinflammatory mechanism was revealed in that pressure-induced exocytosis of P-selectin was inhibited by both antioxidants and mitochondrial inhibitors, indicating that the exocytosis was driven by mitochondrial ROS. In this signaling pathway mitochondria coupled pressure-induced Ca2+ oscillations to the production of ROS that in turn acted as diffusible messengers to activate P-selectin exocytosis. These findings implicate mitochondrial mechanisms in the lung’s proinflammatory response to pressure elevation and identify mitochondrial ROS as critical to P-selectin exocytosis in lung capillary ECs.

A key event in virus-induced inflammation (leukocyte extravasation through the endothelium) is the local activation of endothelial cells, as indicated by the expression of adhesion molecules such as intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and E-selectin. In order to identify triggers of inflammation in adenovirus infection, we inoculated respiratory and ocular epithelial cells with adenovirus type 37 (Ad37), a human pathogen associated with keratoconjunctivitis as well as urogenital and respiratory infections. Fluids from virus-infected epithelial cells activated ICAM-1 (and to a lesser extent, VCAM-1) expression on cultured human umbilical vein endothelial cells. Blocking studies with anticytokine antibodies implicated interleukin-1α (IL-1α) as the epithelial cell-derived factor which activated endothelial cell ICAM-1 expression. The results thus identify epithelial cell-derived IL-1α as a potentially important activator of endothelial cells in Ad37-induced inflammation.

Endothelial responses may contribute importantly to the pathology of high vascular pressure. In lung venular capillaries, we determined endothelial [Ca2+]i by the fura-2 ratioing method and fusion pore formation by quantifying the fluorescence of FM1-43. Pressure elevation increased endothelial [Ca2+]i. Concomitantly evoked exocytotic events were evident in a novel spatial-temporal pattern of fusion pore formation. Fusion pores formed predominantly at vascular branch points and colocalized with the expression of P-selectin. Blockade of mechanogated Ca2+ channels inhibited these responses, identifying entry of external Ca2+ as the critical triggering mechanism. These endothelial responses point to a proinflammatory effect of high vascular pressure that may be relevant in the pathogenesis of pressure-induced lung disease.

J. Clin. Invest. 104:495-502 (1999).

The cytokines IL-1 and TNF-α are involved in inflammation and their production is stimulated by various agents, especially endotoxin (LPS). Here, using the human IL-1 receptor antagonist (IL-1RA) and a new monoclonal antibody (mAb 7F11) to rabbit TNF, the role of endogenous IL-l and TNF production in acute (3h) leukocyte (PMNL) recruitment to dermal inflammation in rabbits has been studied. IL-1RA inhibited by 27% the PMNL accumulation in reactions induced by killed Escherichia coli (p < 0.05) but not by LPS. The monoclonal antibody to TNF inhibited by 27% and 38% (p < 0.002) the PMNL accumulation in LPS and E. coli reactions respectively, but a combination of the mAb with IL-1RA was not more effective. Treatment of human umbilical vein endothelium with LPS for 3 h activated endothelium to induce PMNL transendothelial migration in vitro, which was not inhibited by IL-1RA, antibody to TNF-α, IL-1 or to IL-8. In conclusion, TNF and IL-1 may partially mediate acute PMNL infiltration in vivo to LPS and Gram negative bacteria, but there is a major IL-1/TNF independent mechanism, at least in dermal inflammation, which may be due to direct LPS activation of the microvasculature or perhaps the generation of cytokines other than IL-1 and TNF.

Bacterial invasion of the tissues often stimulates a vigorous inflammatory reaction, which may limit the spread of microorganisms but may also be accompanied by serious vascular injury and tissue damage. We previously studied the inflammatory reaction induced by the injection of killed Escherichia coli into rabbit skin, a model suitable for the quantitation of various parameters of inflammation. Here we report the effect of immune serum treatment of the E. coli on their capacity to induce inflammation and vascular injury. Injection of killed E. coli treated with immune serum elicited a reaction which had a smaller increase in vascular permeability (protein exudation), measured with 125I-labeled albumin, less increase in blood flow, measured with 86RbCl, less leukocyte infiltration, measured with 51Cr-labeled leukocytes, and a lesser degree of hemorrhage, measured with 59Fe-labeled erythrocytes, than E. coli treated with nonimmune serum. Crossover experiments with four different E. coli serotypes and four different antisera indicated that antibody to specific O antigens or a related antigen, but not to K or H antigen, was important for modifying the inflammatory response. Treatment of four different E. coli serotypes with antiserum to “core” glycolipid, produced by immunization with the E. coli J5 mutant, inhibited the inflammatory response to all four E. coli serotypes. Finally, treatment of killed E. coli with polymyxin B also inhibited their inflammation-inducing potential. These results suggest that it may be possible to diminish the magnitude of local vascular and tissue injury associated with E. coli infections by the use of antisera or polymyxin B, which bind to endotoxin on the E. coli.

Escherichia coli organisms induce polymorphonuclear leukocyte (PMNL) infiltration during clinical infection and also in a rabbit dermal model of inflammation. We investigated the factors which may mediate this host response to E. coli. In vitro incubation of Formalin-killed E. coli in heat-inactivated rabbit plasma or balanced salt solution generated in the supernatant factors which induced in vivo PMNL infiltration upon intradermal injection into rabbits. However, these supernatants, in the presence or absence of plasma, did not induce PMNL migration in vitro. The in vivo activity was stable at 100°C and of high molecular weight (30,000). Antiserum to O antigen or to core glycolipid, but not to K or H antigen, as well as polymyxin B inhibited the release or activity of these E. coli-derived factors. The intradermal injection of 0.02 to 0.2 μg of four different endotoxin preparations or lipid A also induced marked PMNL infiltration in vivo. However, these preparations did not stimulate PMNL migration in vitro and failed to generate chemotactic activity in plasma except at very high concentrations (500 μg/ml). Anti-O serum inhibited PMNL infiltration induced by endotoxins with the corresponding O antigen and anti-core glycolipid serum inhibited all four endotoxins tested, whereas polymyxin B inhibited the activity of the endotoxins as well as that of lipid A. Base hydrolysis of endotoxin abolished PMNL infiltration. It is concluded that (i) endotoxin shed from E. coli (killed or live) may be one factor mediating the PMNL infiltration induced by this organism, (ii) endotoxin probably acts independent of in vivo complement activation, (iii) the activity is dependent on the lipid A moiety, and (iv) antibody binding to O or core glycolipid antigens can modify endotoxin so as to diminish its capacity to induce PMNL infiltration in vivo.

Neutrophils are important effector cells in the defense against microorganisms. They migrate into infected sites and then phagocytose and kill bacteria. Chemotactic factors may be important for initiating neutrophil migration. We investigated whether chemotactic factors might also influence an event subsequent to chemotaxis, namely bacterial killing. It was found that preincubation (20 min at 37°C) of human leukocytes with chemotactic substances such as zymosan-activated serum, a C5a-containing fraction of zymosan-activated serum, N-formyl methionyl phenylalanine or N-formyl methionyl-leucine-phenylalanine, enhanced leukocyte killing of Staphylococcus aureus, Escherichia coli, and Streptococcus faecalis in a dose-dependent fashion. The concentration of chemotactic factor required to enhance killing was similar to that required to induce neutrophil chemotaxis. In addition, zymosan-activated serum, C5a fraction, and the two N-formyl methionyl peptides increased the hexose monophosphate shunt activity of resting and phagocytosing neutrophils by two- to threefold. In contrast, bacterial killing by sodium azide-treated neutrophils and neutrophils from a patient with chronic granulomatous disease was not increased by any chemotactic factor. These findings suggest that chemotactic factors stimulate neutrophil oxygen-dependent microbicidal pathways. These observations illustrate another important contribution of biologically active molecules to effector cell function and host defense.

Autosomal recessive interleukin-1 receptor-associated kinase (IRAK)-4 and myeloid differentiation factor (MyD)88 deficiencies impair Toll-like receptor (TLR)- and interleukin-1 receptor-mediated immunity. We documented the clinical features and outcome of 48 patients with IRAK-4 deficiency and 12 patients with MyD88 deficiency, from 37 kindreds in 15 countries. The clinical features of IRAK-4 and MyD88 deficiency were indistinguishable. There were no severe viral, parasitic, and fungal diseases, and the range of bacterial infections was narrow. Noninvasive bacterial infections occurred in 52 patients, with a high incidence of infections of the upper respiratory tract and the skin, mostly caused by Pseudomonas aeruginosa and Staphylococcus aureus, respectively. The leading threat was invasive pneumococcal disease, documented in 41 patients (68%) and causing 72 documented invasive infections (52.2%). P. aeruginosa and Staph. aureus documented invasive infections also occurred (16.7% and 16%, respectively, in 25% and 25% of patients). Systemic signs of inflammation were usually weak or delayed. The first invasive infection occurred before the age of 2 years in 53 (88.3%) and in the neonatal period in 19 (32.7%) patients. Multiple or recurrent invasive infections were observed in most survivors (n = 36/50, 72%).

PIWIL2, a member of PIWI/AGO gene family, is expressed in the germline stem cells (GSCs) of testis for gametogenesis but not in adult somatic and stem cells. It has been implicated to play an important role in tumor development. We have previously reported that precancerous stem cells (pCSCs) constitutively express Piwil2 transcripts to promote their proliferation. Here we show that these transcripts de facto represent Piwil2-like (PL2L) proteins. We have identified several PL2L proteins including PL2L80, PL2L60, PL2L50 and PL2L40, using combined methods of Gene-Exon-Mapping Reverse Transcription Polymerase Chain Reaction (GEM RT-PCR), bioinformatics and a group of novel monoclonal antibodies. Among them, PL2L60 rather than Piwil2 and other PL2L proteins is predominantly expressed in various types of human and mouse tumor cells. It promotes tumor cell survival and proliferation in vitro through up-regulation of Stat3 and Bcl2 gene expressions, the cell cycle entry from G0/1 into S-phase, and the nuclear expression of NF-κB, which contribute to the tumorigenicity of tumor cells in vivo. Consistently, PL2L proteins rather than Piwil2 are predominantly expressed in the cytoplasm or cytoplasm and nucleus of euchromatin-enriched tumor cells in human primary and metastatic cancers, such as breast and cervical cancers. Moreover, nuclear PL2L proteins are always co-expressed with nuclear NF-κB. These results reveal that PL2L60 can coordinate with NF-κB to promote tumorigenesis and might mediate a common pathway for tumor development without tissue restriction. The identification of PL2L proteins provides a novel insight into the mechanisms of cancer development as well as a novel bridge linking cancer diagnostics and anticancer drug development.