Activation of leukotriene B_(4)receptor 1 is a prerequisite for complement receptor 3-mediated antifungal responses of neutrophils

Invasive fungal infections are life-threatening,and neutrophils are vital cells of the innate immune system that defend against them.The role of LTA4H-LTB_(4)-BLT1 axis in regulation of neutrophil responses to fungal infection remains poorly understood.Here,we demonstrated that the LTA4H-LTB_(4)-BLT1 axis protects the host against Candida albicans and Aspergillus fumigatus,but not Cryptococcus neoformans infection,by regulating the antifungal activity of neutrophils.Our results show that deleting Lta4h or Blt1 substantially impairs the fungal-specific phagocytic capacity of neutrophils.Moreover,defective activation of the spleen tyrosine kinase(Syk)and extracellular signal-related kinase(ERK1/2)pathways in neutrophils accompanies this impairment.Mechanistically,BLT1 regulates CR3-mediated,β-1,3-glucan-induced neutrophil phagocytosis,while a physical interaction with CR3 with slight influence on its dynamics is observed.Our findings thus demonstrate that the LTA4H-LTB_(4)-BLT1 axis is essential for the phagocytic function of neutrophils in host antifungal immune response against Candida albicans and Aspergillus fumigatus.

Gene testing for osteonecrosis of the femoral head in systemic lupus erythematosus using targeted next-generation sequencing:A pilot study

BACKGROUND Previous publications indicated that genetic predisposition might play important roles in the onset of osteonecrosis of the femoral head(ONFH)in systemic lupus erythematosus(SLE).Some gene loci such as complement C3d receptor 2(CR2),nitric oxide synthase 3(NOS3),collagen type II alpha 1 chain(COL2A1),protein tyrosine phosphatase non-receptor type 22(PTPN22),and transient receptor potential cation channel subfamily V member 4(TRPV4)were reported to be involved in this process.AIM To investigate whether the risk of ONFH in SLE is associated with single nucleotide variations(SNVs)in these five genes.METHODS SNVs in the CR2,NOS3,COL2A1,PTPN22,and TRPV4 genes were examined by using FastTarget and Illumina Miseq sequencing technologies in 49 cases of SLE with ONFH.Burrows–wheeler aligner was used to align the sequencing reads to hg19,and GATK and Varscan programs were used to perform SNV calling.PolyPhen-2,SIFT,and MutationTaster were used to assess the functional effects of non-synonymous SNVs.RESULTS Six of the 49 patients were confirmed to have low frequency SNVs,including one patient with SNVs in NOS3(exon 6:c.814G>A:p.E272K and exon 7:c.814G>A:p.E272K.),four in COL2A1(rs41263847:exon 29:c.1913C>T:p.T638I,exon 28:c.1706C>T:p.T569I,and rs371445823:exon 8:c.580G>A:p.A194T,exon 7:c.373G>A:p.A125T),and one in CR2(rs45573035:exon 2:c.200C>G:p.T67S).CONCLUSION The onset of ONFH in SLE might be associated with the identified SNVs in NOS3,COL2A1,and CR2.

Complement 5a receptor-mediated neutrophil dysfunction is associated with a poor outcome in sepsis

Complement 5a （C5a） has been implicated in the pathogenesis of sepsis by inducing the functional impairment of neutrophils; however, the utility of C5a receptors （C5aRs; C5aR and C5L2） as biomarkers for the management of sepsis is uncertain. This study investigated the dynamic expression of C5aR and C5L2 on neutrophits and their effects on neutrophil function. We found that sepsis patients displayed low expression levels of C5aR and C5L2 on neutrophils compared to healthy and systemic inflammatory response syndrome （SIRS） subjects, and this expression pattern was correlated with disease severity. Additionally, the expression levels of C5aR and C5L2 were associated with the survival of sepsis patients. In vitro, the addition of C5a significantly reduced C5aR and C5L2 expression levels and IL-8 production in neutrophils from sepsis patients. Those findings suggest that the reduced expression of C5aRs was associated with the functional impairment of neutrophils and a poor prognosis for sepsis patients. Overall, these findings may help establish C5aRs expression levels as early markers to predict the severity of sepsis.

Activation of mitogen activated protein kinases via complement receptor type 2

Background Complement receptor type 2 (CR2) is the receptor for C3d and C3dg and for Epstein Barr virus The aim of our study was to explore whether CR2 can independently mediate the activation of mitogen activated protein kinases (MAPKs, including ERK, JNK, and p38MAPK), and to highlight the molecular mechanism of CD 4 + cell deletion in AIDS Methods HOS cells (HOS CR2) and HOS CD4 cells (HOS CD4CR2) stably expressing CR2 were established and then identified by FACS and Western blotting Activation and blocking tests of MAPKs were assessed by Western blot Cell proliferation was determined using Cell Titer 96 Aqueous One Solution Reagent Results FACS results showed that the positive rates of HOS CR2 and HOS CD4CR2 cells were greater than 96%, and Western blot showed that the CR2 expression levels on HOS CR2 and HOS CD4CR2 cells were high Activation and blocking tests of MAPKs (ERK, JNK, and p38MAPK) were carried out in HOS CR2, HOS CD4, and HOS CD4CR2 cells The activation of MAPKs in HOS CR2 cells stimulated with PMA (100 ng/ml) and NHS (10%) was identical The activation of MAPKs increased at 5 minutes, reached a peak at 10 minutes, and decreased to baseline within 30 minutes, all in a time dependent manner; the activation of MAPKs was blocked by anti CR2 McAb, PD98059 (inhibitor of ERK), and Wortmanin (inhibitor of PI 3K), respectively In HOS CD4 cells, MAPKs were activated by HIV gp160 In HOS CD4CR2 cells, MAPK activation was induced by HIV gp160, 10% NHS, and HIV gp160+10%NHS; phosphorylation of p38MAPK was dramatically induced by HIV gp160+NHS, and lasted for 1 hour The cell proliferation results showed that HIV gp160 inhibited the proliferation of HOS CD4 and HOS CD4CR2 cells ( P <0 01) and that NHS enhanced the effect of HIV gp160 ( P <0 01) Conclusions The activation of MAPKs is independently mediated by CR2 and that anti CR2 McAb, PD98059, and Wortmanin block the activation of MAPKs, respectively The results of the signal transduction and cell proliferation assays of HOS CD4CR2 cells show that CR2 plays a role in the pathogenesis of HIV infection, especially in the inhibition of CD 4 + cell proliferation

Function and regulation of self-reactive marginal zone B cells in autoimmune arthritis

Polyreactive innate-type B cells account for many B cells expressing self-reactivity in the periphery. Improper regulation of these B cells may be an important factor that underlies autoimmune disease. Here we have explored the influence of self-reactive innate B cells in the development of collagen-induced arthritis （CIA）, a mouse model of rheumatoid arthritis. We show that splenic marginal zone （MZ）, but not B- 1 B cells exhibit spontaneous IgM reactivity to autologous collagen II in na＇=＇ve mice. Upon immunization with heterologous collagen II in complete Freund＇s adjuvant the collagen-reactive MZ B cells expanded rapidly, while the B-1 B cells showed a modest anti-collagen response. The MZ B cells were easily activated by toll-like receptor （TLR） 4 and 9-1igands in vitro, inducing proliferation and cytokine secretion, implying that dual engagement of the B-cell receptor and TLRs may promote the immune response to self-antigen. Furthermore, collagen-primed MZ B cells showed significant antigen-presenting capacity as reflected by cognate T-cell proliferation in vitroand induction of IgG anti-collagen antibodies in vivo. MZ B cells that were deficient in complement receptors I and 2 demonstrated increased proliferation and cytokine production, while Fcy receptor lib deficiency of the cells lead to increased cytokine production and antigen presentation. In conclusion, our data highlight self-reactive MZ B cells as initiators of the autoimmune response in CIA, where complement and Fc receptors are relevant in controlling the self-reactivity in the cells.