Immune Response of Healthy Adults to the Ingested Probiotic Lactobacillus casei Shirota

Daily ingestion of a probiotic drink containing Lactobacillus casei Shirota (LcS; 1.3 × 10¹⁰ live cells) by healthy adults for (1) 4‐week LcS, (2) 6‐week discontinuation of LcS and (3) a final 4 weeks of LcS was investigated. There was a significant increase in expression of the T cell activation marker CD3⁺CD69⁺ in ex vivo unstimulated blood cells at weeks 10 and 14, and there was a significant increase in the NK cell marker CD3⁺CD16/56⁺ in ex vivo unstimulated blood cells at weeks 4, 10 and 14. Expression of the NK cell activation marker CD16/56⁺CD69⁺ in ex vivo unstimulated blood cells was 62% higher at week 10 and 74% higher at week 14. Intracellular staining of IL‐4 in ex vivo unstimulated and PMA‐/ionomycin‐stimulated CD3⁺ β7⁺ integrin blood cells was significantly lower at weeks 10 and 14. Intracellular staining of IL‐12 in ex vivo unstimulated and LPS‐stimulated CD14⁺ blood cells was significantly lower at weeks 4, 10 and 14. Intracellular staining of TNF‐α in LPS‐stimulated CD14⁺ blood cells was significantly lower at weeks 4, 10 and 14. Mucosal salivary IFN‐γ, IgA1 and IgA2 concentrations were significantly higher at week 14, but LcS did not affect systemic circulating influenza A‐specific IgA or IgG and tetanus‐specific IgG antibody levels. In addition to the decrease in CD3⁺β7⁺ integrin cell IL‐4 and a reduced CD14⁺ cell pro‐inflammatory cytokine profile, at week 14 increased expression of activation markers on circulating T cells and NK cells and higher mucosal salivary IgA1 and IgA2 concentration indicated a secondary boosting effect of LcS.     

Innate,antigen‐independent role for T cells in the activation of the immune system by Propionibacterium acnes

Propionibacterium acnes is a human commensal but also an opportunistic pathogen. In mice, P. acnes exerts strong immunomodulatory activities, including formation of intrahepatic granulomas and induction of LPS hypersensitivity. These activities are dependent on P. acnes recognition via TLR9 and subsequent IL‐12‐mediated IFN‐γ production. We show that P. acnes elicits IL‐12p40 and p35 mRNA expression in macrophages, and IFN‐γ mRNA in liver CD4⁺ T cells and NK cells. After priming with P. acnes, CD4⁺ T cells serve as the major IFN‐γ mRNA source. In the absence of CD4⁺ T cells, CD8⁺ T cells (regardless of antigenic specificity) or NK cells can produce sufficient IFN‐γ to induce the P. acnes‐driven immune effects. Moreover, in the absence of αβT cells, γδT cells also enable the development of strongly enhanced TNF‐α and IFN‐γ responses to LPS and intrahepatic granuloma formation. Thus, under microbial pressure, different T‐cell types, independent of their antigen specificity, exert NK‐cell‐like functions, which contribute decisively to the activation of the innate immune system.     

Combined cell wall polysaccharide,mycotoxin and bacterial lipopolysaccharide exposure and inflammatory cytokine responses

Human exposure to environmental microbes occurs regularly. Microbial compounds may interact with each other to affect cellular responses. We hypothesized that interactions between microbial compounds could modulate inflammatory cytokine responses in vitro. We investigated monocyte production of the pro‐inflammatory cytokine tumour necrosis factor‐α (TNF‐α) and the regulatory cytokine interleukin‐10 (IL‐10) after combined exposure to the fungal cell wall polysaccharide mannan and to the β‐glucan laminarin, the mycotoxin citrinin and bacterial lipopolysaccharide (LPS). Interactions between the cell wall microbial compounds were estimated statistically in a general linear mixed model. We found that LPS (100 ng/ml) and the used β‐glucan (up to 1000 μg/ml) significantly interacted with each other to reduce TNF‐α production. Mannan (up to 100 μg/ml) did not interact with the β‐glucan, but interacted with LPS. IL‐10 production was induced by LPS only. The mycotoxin citrinin did not induce cytokine production, but was toxic to the cells in a dose‐ and time‐dependent manner. However, non‐toxic doses of citrinin reduced LPS‐induced IL‐10 production while LPS‐induced TNF‐α production was not similarly reduced by citrinin. In conclusion, interactions between microbial compounds can modulate cellular inflammatory cytokine production and experimental investigations of one compound at a time could give misleading conclusions about these combined effects.     

Cells with regulatory function of the innate and adaptive immune system in primary Sjögren's syndrome

The aim of the present study was to describe subsets of cells with regulatory properties in primary Sjögren's syndrome (pSS), and to correlate these cell populations with clinical symptoms. Among the 32 investigated patients, 23 had extraglandular manifestations (EGMs), while nine had only glandular symptoms. Twenty healthy individuals served as controls. The percentages of natural killer (NK), natural killer T cells (NK T), interleukin (IL)‐10 producing T regulatory type 1 (Tr1) cells and CD4⁺CD25⁺ regulatory T cells (T_reg) cells were determined by flow cytometry and serum cytokine levels of IL‐4, IL‐6, IL‐10, tumour necrosis factor (TNF)‐α and interferon (IFN)‐γ were evaluated by enzyme‐linked immunosorbent assay (ELISA). Functional tests were carried out to assess the suppressor properties of T_reg cells in patients and controls. Peripheral NK, NK T and Tr1 cell percentages were elevated in pSS, while CD4⁺CD25⁺ T_reg cells showed reduced frequencies in patients compared to controls. In pSS, elevated percentages of NK T, Tr1 and CD4⁺CD25⁺ T_reg cells were observed in patients with EGMs, when compared to patients with sicca symptoms only. CD4⁺CD25⁺ T_reg cell percentages showed a negative correlation with sialometry values. The in vitro functional assay demonstrated lower suppression activity of CD4⁺CD25⁺ T_reg cells in patients compared to controls. Serum IL‐6 and TNF‐α levels were elevated, while IL‐10 was decreased in patients compared to controls. Negative correlation was found between IL‐10 levels and the percentages of Tr1 cells. Changes in the investigated subsets of regulatory cells in pSS may contribute to the development and progression of the disease.     

Correlation Between Natural Cytotoxicity Receptors and Intracellular Cytokine Expression of Peripheral Blood NK Cells in Women with Recurrent Pregnancy Losses and Implantation Failures

Problem Natural cytotoxicity receptors (NCRs) are unique markers, which regulate NK cell cytotoxicity and cytokine production. We investigated whether women with recurrent pregnancy losses (RPLs) and implantation failures have aberrant correlation between NCRs and intracellular cytokine expression of NK cells. Method of study Peripheral blood NK cells (CD56^dim and CD56^bright) were analyzed for NCRs (NKp46, NKp44 and NKp30) and cytokine expression (TNF‐α, IFN‐γ, IL‐4, IL‐10) using flow cytometry in RPL (n = 22), implantation failures (n = 23) or controls (n = 15). Results In type 1 cytokine studies, CD56^bright/NKp30⁺ cells in controls (r = 0.696, P < 0.05) were positively correlated with CD56^bright/IFN‐γ⁺/TNF‐α⁺ cells. CD56^bright/NKp46⁺ cells in implantation failures (r = ?0.76, P < 0.01) were negatively correlated with CD56^bright/IFN‐γ⁺/TNF‐α^? cells. RPL did not have any correlation. In type 2 cytokine studies, CD56⁺/NKp46⁺ cells (r = 0.758, P < 0.01) and CD56⁺/NKp30⁺ cells (r = 0.637, P < 0.05) were positively correlated with CD56^bright/IL‐4⁺/IL‐10⁺ cells in controls. CD56⁺/NKp30⁺ cells in implantation failures (r = ?0.778, P < 0.05) were negatively correlated with CD56^bright/IL‐10⁺/IL‐4⁺ cells. There were no correlations in RPL. Conclusion Recurrent pregnancy losses and implantation failures have lack of, or negative correlation between NCRs and intracellular cytokines expression. This observation suggests that excessive pro‐inflammatory cytokine expression in NK cells in RPL and implantation failures may be exerted through the NCRs or interruption of signal transduction processes.     

IL‐18‐induced expression of high‐affinity IL‐2R on murine NK cells is essential for NK‐cell IFN‐γ production during murine Plasmodium yoelii infection

Early production of pro‐inflammatory cytokines, including IFN‐γ, is essential for control of blood‐stage malaria infections. We have shown that IFN‐γ production can be induced among human natural killer (NK) cells by coculture with Plasmodium falciparum infected erythrocytes, but the importance of this response is unclear. To further explore the role of NK cells during malaria infection, we have characterized the NK‐cell response of C57BL/6 mice during lethal (PyYM) or nonlethal (Py17XNL) P. yoelii infection. Ex vivo flow cytometry revealed that NK cells are activated within 24 h of Py17XNL blood‐stage infection, expressing CD25 and producing IFN‐γ; this response was blunted and delayed during PyYM infection. CD25 expression and IFN‐γ production were highly correlated, suggesting a causal relationship between the two responses. Subsequent in vitro experiments revealed that IL‐18 signaling is essential for induction of CD25 and synergizes with IL‐12 to enhance CD25 expression on splenic NK cells. In accordance with this, Py17XNL‐infected erythrocytes induced NK‐cell CD25 expression and IFN‐γ production in a manner that is completely IL‐18‐ and partially IL‐12‐dependent, and IFN‐γ production is enhanced by IL‐2. These data suggest that IL‐2 signaling via CD25 amplifies IL‐18‐ and IL‐12‐mediated NK‐cell activation during malaria infection.     

IL‐33 promotes innate IFN‐γ production and modulates dendritic cell response in LCMV‐induced hepatitis in mice

Recent studies have revealed IL‐33 as a key factor in promoting antiviral T‐cell responses. However, it is less clear as to how IL‐33 regulates innate immunity. In this study, we infected wild‐type (WT) and IL‐33^?/? mice with lymphocytic choriomeningitis virus and demonstrated an essential role of infection‐induced IL‐33 expression for robust innate IFN‐γ production in the liver. We first show that IL‐33 deficiency resulted in a marked reduction in the number of IFN‐γ⁺ γδ T and NK cells, but an increase in that of IL‐17⁺ γδ T cells at 16 h postinfection. Recombinant IL‐33 (rIL‐33) treatment could reverse such deficiency via increasing IFN‐γ‐producing γδ T and NK cells, and inhibiting IL‐17⁺ γδ T cells. We also found that rIL‐33‐induced type 2 innate lymphoid cells were not involved in T‐cell responses and liver injury, since the adoptive transfer of type 2 innate lymphoid cells neither affected the IFN‐γ and TNF‐α production in T cells, nor liver transferase levels in lymphocytic choriomeningitis virus infected mice. Interestingly, we found that while IL‐33 was not required for costimulatory molecule expression, it was critical for DC proliferation and cytokine production. Together, this study highlights an essential role of IL‐33 in regulating innate IFN‐γ‐production and DC function during viral hepatitis.     

The two‐pore domain K2P channel TASK2 drives human NK‐cell proliferation and cytolytic function

Natural killer (NK) cells are a subset of cytotoxic lymphocytes that recognize and kill tumor‐ and virus‐infected cells without prior stimulation. Killing of target cells is a multistep process including adhesion to target cells, formation of an immunological synapse, and polarization and release of cytolytic granules. The role of distinct potassium channels in this orchestrated process is still poorly understood. The current study reveals that in addition to the voltage‐gated K_V1.3 and the calcium‐activated K_Ca3.1 channels, human NK cells also express the two‐pore domain K₂P channel TASK2 (TWIK‐related acid‐sensitive potassium channel). Expression of Task2 varies among NK‐cell subsets and depends on their differentiation and activation state. Despite its different expression in TASK2^highCD56^brightCD16^? and TASK2^lowCD56^dimCD16⁺ NK cells, TASK2 is involved in cytokine‐induced proliferation and cytolytic function of both subsets. TASK2 is crucial for leukocyte functional antigen (LFA‐1) mediated adhesion of both resting and cytokine‐activated NK cells to target cells, an early step in killing of target cells. With regard to the following mechanism, TASK2 plays a role in release of cytotoxic granules by resting, but not IL‐15‐induced NK cells. Taken together, our data exhibit two‐pore potassium channels as important players in NK‐cell activation and effector function.     

Characterization of cytokine production by human term placenta macrophages in vitro

Problem Macrophages are apparently the only immune cells within placenta villi, yet functions of these cells remain obscure. It has been postulated that placental macrophages accomplish regulatory roles at the fetal–maternal interface by means of wide variety of secreted cytokines. We attempt to analyze the patterns of cytokine production in an isolated population of placental macrophages. Method of study Macrophages were obtained from term placentas in the absence of spontaneous labor. The basal and lipopolysaccharide (LPS)‐stimulated levels of intracellular cytokines were detected by flow cytometry. The basal cytokine secretion was determined by BD^?Cytometry Bead Array (BD Biosciences, San Diego, CA, USA). Results Intracellular IL‐1α, IL‐1β, IL‐6, and TNFα were detected in 31, 27, 4, and 3% CD68+ cells, respectively. Stimulation with LPS increased the proportions of cytokine‐producing CD68+ cells to 48, 50, 28, and 49%, respectively. Under basal conditions, levels of released TNFα and IL‐6, respectively, were 20‐ and 25‐fold higher when compared with IL‐1β while IL‐10 was secreted in small but detectable amounts. When a secretory activity was estimated for cytokine‐producing cells, the secretion rate for TNFα and IL‐6 overwhelmingly surpassed that for IL‐1β (TNFα:IL‐6:IL‐1β ratio was 192:145:1). Conclusion These results suggest functional heterogeneity of the placental macrophage population and contribute to the elucidation of regulatory roles of these cells in gestation.     

Co‐culture of Spleen Stromal Cells with Bone Marrow Mononuclear Cells Leads to the Generation of A Novel Macrophage Subset

Macrophages adopt diverse activation states depending on the microenvironment. Recently, stromal cells have been demonstrated to be organizers of the microenvironment. Here, using splenic stromal cells to mimic the splenic microenvironment in vivo, we show that spleen stromal cells can programme bone marrow‐derived mononuclear cells to differentiate and polarize into a novel macrophage subset. These differentiated macrophages (Diff‐Mφ) exhibited pronounced production of IL‐10, IL‐6 and TNF‐α, but diminished the production of IL‐12 in response to LPS. The generation of Diff‐Mφ depended on cell–cell contact as well as on soluble factors. Diff‐Mφ directly suppressed the antigen‐non‐specific (CD3/CD28) CD4⁺ T cell proliferative response and induced cell death of activated CD4⁺ T cells. As for cytokine production in CD4⁺ T cells, Diff‐Mφ promoted IL‐10 and IL‐17 production, whereas inhibited IL‐4 production and did not alter IFN‐γ production. Besides, Diff‐Mφ also expressed iNOS, CD16/CD32, CD54, CD43, CCR7, CD44, PD‐L1 and FasL, which might be involved in the function of Diff‐Mφ. These results suggest that splenic microenvironment may physiologically induce a novel type of macrophages differentiation.     

Activation of p38 mitogen-activated protein kinase is critical step for acquisition of effector function in cytokine-activated T cells, but acts as a negative regulator in T cells activated through the T-cell receptor

Peripheral blood CD4⁺ CD45RO⁺ T cells activated in vitro are able to induce expression of tumour necrosis factor‐α (TNF‐α) in monocytes via a contact‐dependent mechanism. Activation is achieved either with interleukin‐2 (IL‐2)/IL‐6/TNF‐α over an 8‐day period or cross‐linking CD3 using anti‐CD3 antibody for 48 hr. In this paper, we show that the p38 mitogen‐activated protein kinase (MAPK) signalling pathway played different roles in the generation of effector function in these two types of activated T cells. In anti‐CD3 activated T cells, p38 MAPK is a negative regulator for anti‐CD3 induced cell proliferation and has no significant effect on the acquisition of either the effector function (induction of monocyte‐derived TNF‐α) or production of T‐cell cytokines. In contrast, the p38 MAPK signalling pathway is required for the acquisition of cytokine‐induced effector function and promotes cell proliferation and cytokine production.     

Soluble HLA‐I‐mediated secretion of TGF‐β1 by human NK cells and consequent down‐regulation of anti‐tumor cytolytic activity

Soluble HLA class I (sHLA‐I) molecules can regulate survival of NK cells and their anti‐tumor killing activity. Herein, we have analysed whether interaction of sHLA‐I with CD8 and/or different isoforms of killer Ig‐like receptors (KIR) induced secretion of transforming growth factor (TGF)‐β1. CD8⁺KIR^? NK cell clones secreted TGF‐β1 upon the interaction of sHLA‐I with CD8 molecule. sHLA‐Cw4 or sHLA‐Cw3 alleles engaging inhibitory isoforms of KIR, namely KIR2DL1 or KIR2DL2, strongly downregulated TGF‐β1 production elicited through CD8. On the other hand, sHLA‐Cw4 or sHLA‐Cw3 alleles induced secretion of TGF‐β1 by ligation of stimulatory KIR2DS1 or KIR2DS2 isoforms. TGF‐β1 strongly reduced NK cell‐mediated tumor cell lysis and production of pro‐inflammatory cytokines such as TNF‐α and IFN‐γ. Also, TGF‐β1 inhibited NK cell cytolysis induced by the engagement of stimulatory receptors including NKG2D, DNAM1, 2B4, CD69, NKp30, NKp44 and NKp46. The IL‐2‐dependent surface upregulation of some of these receptors was prevented by TGF‐β1. Furthermore, TGF‐β1 hampered IL‐2‐induced NK cell proliferation but not IL‐2‐mediated rescue from apoptosis of NK cells. Depletion of TGF‐β1 restored all the NK cell‐mediated functional activities analysed. Taken together these findings suggest that sHLA‐I antigens may downregulate the NK cell‐mediated innate response by inducing TGF‐β1 release.     

Secreted aspartic proteases of Candida albicans activate the NLRP3 inflammasome

In a recent report, we demonstrated that distinct members of the secreted aspartic protease (Sap) family of Candida albicans are able to induce secretion of proinflammatory cytokines by human monocytes, independently of their proteolytic activity and specific pH optima. In particular, C. albicans Sap2 and Sap6 potently induced IL‐1β, TNF‐α, and IL‐6 production. Here, we demonstrate that Sap2 and Sap6 proteins trigger IL‐1β and IL‐18 production through inflammasome activation. This occurs via NLRP3 and caspase‐1 activation, which cleaves pro‐IL‐1β into secreted bioactive IL‐1β, a cytokine that was induced by Saps in monocytes, in monocyte‐derived macrophages and in dendritic cells. Downregulation of NLRP3 by RNA interference strongly reduced the secretion of bioactive IL‐1β. Inflammasome activation required Sap internalization via a clathrin‐dependent mechanism, intracellular induction of K⁺ efflux, and ROS production. Inflammasome activation of monocytes induced by Sap2 and Sap6 differed from that induced by LPS‐ATP in several aspects. Our data reveal novel immunoregulatory mechanisms of C. albicans and suggest that Saps contribute to the pathogenesis of candidiasis by fostering rather than evading host immunity.     

NK cells modulate the lung dendritic cell‐mediated Th1/Th17 immunity during intracellular bacterial infection

The impact of the interaction between NK cells and lung dendritic cells (LDCs) on the outcome of respiratory infections is poorly understood. In this study, we investigated the effect and mechanism of NK cells on the function of LDCs during intracellular bacterial lung infection of Chlamydia muridarum in mice. We found that the naive mice receiving LDCs from C. muridarum‐infected NK‐cell‐depleted mice (NK‐LDCs) showed more serious body weight loss, bacterial burden, and pathology upon chlamydial challenge when compared with the recipients of LDCs from infected sham‐treated mice (NK+LDCs). Cytokine analysis of the local tissues of the former compared with the latter exhibited lower levels of Th1 (IFN‐γ) and Th17 (IL‐17), but higher levels of Th2 (IL‐4), cytokines. Consistently, NK‐LDCs were less efficient in directing C. muridarum‐specific Th1 and Th17 responses than NK+LDCs when cocultured with CD4⁺ T cells. In NK cell/LDC coculture experiments, the blockade of NKG2D receptor reduced the production of IL‐12p70, IL‐6, and IL‐23 by LDCs. The neutralization of IFN‐γ in the culture decreased the production of IL‐12p70 by LDCs, whereas the blockade of TNF‐α resulted in diminished IL‐6 production. Our findings demonstrate that NK cells modulate LDC function to elicit Th1/Th17 immunity during intracellular bacterial infection.     

T cell response to viral antigens in adults and children with common variable immunodeficiency and specific antibody deficiency

Several T cell abnormalities have been described in common variable immunodeficiency (CVID), a B cell disorder of mainly unknown origin. A subset of CVID patients suffers from frequent reactivations of herpes viruses. We studied T cell function in CVID [and in a subset of paediatric patients with specific antibody deficiency (SAD)] by measuring T cell proliferation and cytokine production in response to herpes virus‐antigens in paediatric CVID patients (n = 9) and paediatric SAD patients (n = 5), in adult CVID patients (n = 14) and in healthy controls. Paediatric CVID patients, but not SAD patients, displayed moderately increased CD8⁺ T cell proliferation in response to cytomegalovirus, human herpes virus type 6B (HHV6‐B) and herpes simplex virus compared to controls. CD8⁺ T cell responses in adult CVID patients tended to be increased in response to cytomegalovirus and herpes simplex virus. In response to stimulation with herpes virus antigens, the proinflammatory cytokines interleukin (IL)‐1β, IL‐6, tumour necrosis factor (TNF)‐α and interferon inducible protein (IP)‐10 were produced. Overall, no major differences were detected in cytokine production upon stimulation between patients and controls, although higher IL‐10 and IL‐12 production was detected in paediatric patients. In conclusion, cellular immunity against herpes virus antigens appears undisturbed in CVID patients, although defects in subpopulations of CVID patients cannot be excluded.     

Anti-tumour synergy of cytotoxic chemotherapy and anti-CD40 plus CpG-ODN immunotherapy through repolarization of tumour-associated macrophages

We studied the effectiveness of monoclonal anti‐CD40 + cytosine–phosphate–guanosine‐containing oligodeoxynucleotide 1826 (CpG‐ODN) immunotherapy (IT) in mice treated with multidrug chemotherapy (CT) consisting of vincristine, cyclophosphamide and doxorubicin. Combining CT with IT led to synergistic anti‐tumour effects in C57BL/6 mice with established B16 melanoma or 9464D neuroblastoma. CT suppressed the functions of T cells and natural killer (NK) cells, but primed naïve peritoneal macrophages (Mφ) to in vitro stimulation with lipopolysaccharide (LPS), resulting in augmented nitric oxide (NO) production. IT, given after CT, did not restore the responsiveness of T cells and NK cells, but further activated Mφ to secrete NO, interferon‐γ (IFN‐γ) and interleukin (IL)‐12p40 and to suppress the proliferation of tumour cells in vitro. These functional changes were accompanied by immunophenotype alterations on Mφ, including the up‐regulation of Gr‐1. CD11b⁺ F4/80⁺ Mφ comprised the major population of B16 tumour‐infiltrating leucocytes. CT + IT treatment up‐regulated molecules associated with the M1 effector Mφ phenotype [CD40, CD80, CD86, major histocompatibility complex (MHC) class II, IFN‐γ, tumour necrosis factor‐α (TNF‐α) and IL‐12] and down‐regulated molecules associated with the M2 inhibitory Mφ phenotype (IL‐4Rα, B7‐H1, IL‐4 and IL‐10) on the tumour‐associated Mφ compared with untreated controls. Together, the results show that CT and anti‐CD40 + CpG‐ODN IT synergize in the induction of anti‐tumour effects which are associated with the phenotypic repolarization of tumour‐associated Mφ.     

Pattern and diversity of cytokine production differentiates between Mycobacterium tuberculosis infection and disease

Tuberculosis (TB) remains a global health problem. The solution involves development of an effective vaccine, but has been limited by incomplete understanding of what constitutes protective immunity during natural infection with Mycobacterium tuberculosis. In this study, M. tuberculosis‐specific responses following an overnight whole‐blood assay were assessed by intracellular cytokine staining and luminex, and compared between TB cases and exposed household contacts. TB cases had significantly higher levels of IFN‐γ⁺TNF‐α⁺IL‐2⁺CD4⁺T cells compared with contacts. TB cases also had a significantly higher proportion of cells single‐positive for TNF‐α, but lower proportion of cells producing IL‐2 alone and these differences were seen for both CD4⁺and CD8⁺ T cells. Cytokine profiles from culture supernatants were significantly biased toward a Th1 phenotype (IFN‐γ and IL‐12(p40)) together with a complete abrogation of IL‐17 secretion in TB cases. Our data indicate that despite a robust response to TB antigens in active TB disease, changes in the pattern of cytokine production between TB infection and disease clearly contribute to disease progression.     

Axl/Gas6 pathway positively regulates FLT3 activation in human natural killer cell development

Activation of the fibromyalgia syndrome‐like tyrosine kinase 3 (FLT3) by its ligand, FLT3 ligand (FL), strongly augments the development of natural killer (NK) cells from human CD34⁺ hematopoietic progenitor cells (HPCs) in the presence of IL‐15, compared with NK‐cell development in the presence of IL‐15 alone. In this study, we observed that blocking the receptor tyrosine kinase Axl/Gas6 pathway with a soluble Axl‐IgG1 Fc fusion protein (Axl‐Fc) in the presence of FL significantly diminished the absolute number of CD3^?CD56⁺ NK cells derived from human CD34⁺ HPCs. Axl‐Fc reduced the expression levels of the IL‐2/15 receptor β chain (CD122) and γ chain (CD132) induced by activation of FLT3 and consequently reduced the frequency of NK precursor cells responding to IL‐15. Furthermore, Axl‐Fc diminished FL‐induced FLT3 phosphorylation and impeded the physical interaction between Axl and FLT3 in CD34⁺ HPCs. Collectively, our data suggest that the Axl/Gas6 pathway contributes to normal human NK‐cell development at least in part via its positive regulatory effect on FLT3 signaling in CD34⁺ HPCs.     

Impaired cytokine responses in patients with cryopyrin‐associated periodic syndrome (CAPS)

Cryopyrin‐associated periodic syndrome (CAPS) is characterized by dysregulated inflammation with excessive interleukin (IL)‐1β activation and secretion. Neonatal‐onset multi‐system inflammatory disease (NOMID) is the most severe form. We explored cytokine responses in 32 CAPS patients before and after IL‐1β blocking therapy. We measured cytokines produced by activated peripheral blood monuclear cells (PBMCs) from treated and untreated CAPS patients after stimulation for 48 h with phytohaemagglutinin (PHA), PHA plus IL‐12, lipopolysaccharide (LPS) or LPS plus interferon (IFN)‐γ. We measured IL‐1β, IL‐6, IL‐10, tumour necrosis factor (TNF), IL‐12p70 and IFN‐γ in the supernatants. PBMCs from three untreated CAPS patients were cultured in the presence of the IL‐1β blocker Anakinra. Fifty healthy individuals served as controls. CAPS patients had high spontaneous production of IL‐1β, IL‐6, TNF and IFN‐γ by unstimulated cells. However, stimulation indexes (SIs, ratio of stimulated to unstimulated production) of these cytokines to PHA and LPS were low in NOMID patients compared to controls. Unstimulated IL‐10 and IL‐12p70 production was normal, but up‐regulation after PHA and LPS was also low. LPS plus IFN‐γ inadequately up‐regulated the production of IL‐1β, IL‐6, TNF and IL‐10 in CAPS patients. In‐vitro but not in‐vivo treatment with Anakinra improved SIs by lowering spontaneous cytokine production. However, in‐vitro treatment did not improve the low stimulated cytokine levels. Activating mutations in NLRP3 in CAPS are correlated with poor SIs to PHA, LPS and IFN‐γ. The impairment in stimulated cytokine responses in spite of IL‐1β blocking therapy suggests a broader intrinsic defect in CAPS patients, which is not corrected by targeting IL‐1β.