RESUMO
Dickeya solani is a pathogen most frequently responsible for infecting potato plants in Europe. As in the case of most plant pathogens, its ability to colonize and invade the host depends on chemotaxis and motility. The coordinated movement of Dickeya over solid surfaces is governed by a quorum sensing mechanism. In D. solani motility is regulated by ExpI-ExpR proteins, homologous to luxI-luxR system from Vibrio fisheri, in which N-acyl-homoserine lactones (AHLs) serve as signaling molecules. Moreover, in many Gram-negative bacteria motility is coupled with central metabolism via carbon catabolite repression. This enables them to reach more nutrient-efficient niches. The aim of this study was to analyze the swarming motility of D. solani depending on the volume of the medium in the cultivation plate and glucose content. We show that the ability of this bacterium to move is strictly dependent on both these factors. Moreover, we analyze the production of AHLs and show that the quorum sensing mechanism in D. solani is also influenced by the availability of glucose in the medium and that the distribution of these signaling molecules are different depending on the volume of the medium in the plate.
Assuntos
Acil-Butirolactonas/farmacologia , Proteínas de Bactérias/genética , Dickeya/efeitos dos fármacos , Glucose/farmacologia , Solanum tuberosum/microbiologia , Fatores de Virulência/genética , Acil-Butirolactonas/metabolismo , Proteínas de Bactérias/metabolismo , Quimiotaxia/efeitos dos fármacos , Quimiotaxia/genética , Meios de Cultura/química , Meios de Cultura/farmacologia , Dickeya/genética , Dickeya/metabolismo , Dickeya/patogenicidade , Regulação Bacteriana da Expressão Gênica , Glucose/metabolismo , Doenças das Plantas/microbiologia , Percepção de Quorum/efeitos dos fármacos , Percepção de Quorum/genética , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Transativadores/genética , Transativadores/metabolismo , Fatores de Virulência/metabolismoRESUMO
The objective of this study was to describe a novel form of primary immune disorder characterized by circulating B cells with the exclusive transitional phenotype which fail to respond to CpG stimulation. The 12-year-old male patient suffered from recurrent bacterial infections since infancy. The immunological studies were based on extensive B cell immunophenotyping, humoral in vivo response to different vaccine antigens, and in vitro proliferation and immunoglobulin production after CpG stimulation. Sequence analysis for potentially candidate genes such as IRF8, MyD88, TLR9, T-bet were performed. The patient's serum immunoglobulin levels and the specific antibody response to tetanus toxoid were normal, whereas that to polysaccharide antigens was severely impaired. Flow cytometric analysis showed that almost all patient's peripheral B cells had the transitional phenotype (CD24(bright) CD38(bright) CD27(neg)). Furthermore, the patient's B cells did not proliferate and failed to secrete immunoglobulins after in vitro CpG stimulation. Sequence analysis for TLR9, MyD88, IRF8 and T-bet showed no mutations. To our knowledge, this is the first case of a novel primary immunodeficiency mimicking the clinical phenotype of common variable immunodeficiency, with a peculiar immunological phenotype characterized by normal immunoglobulin serum levels, circulating B cells with the exclusive transitional phenotype unable to respond to CpG stimulation. This defines a novel form of primary immunodeficiency mimicking common variable immunodeficiency in the presence of normal immunoglobulin serum levels.
Assuntos
Subpopulações de Linfócitos B/imunologia , Ilhas de CpG/imunologia , Síndromes de Imunodeficiência/imunologia , Criança , Imunodeficiência de Variável Comum/diagnóstico , Diagnóstico Diferencial , Humanos , Síndromes de Imunodeficiência/diagnóstico , Imunofenotipagem , Ativação Linfocitária/imunologia , Masculino , Infecções Oportunistas/imunologia , Pneumonia Bacteriana/imunologia , RecidivaRESUMO
BLyS, a TNF family member, is crucial for B cell proliferation and differentiation by acting through its three receptors, TACI, BCMA and BAFF-R. The knock out model for BLyS is characterized by an immunological phenotype reminiscent of the human phenotype of common variable immunodeficiency (CVID). CVID is characterized by a defective B cell compartment, evidencing the putative importance of BLyS in its pathogenesis. On the contrary, the transgenic model for BLys is characterized by autoimmune manifestations, underlying its role in B cell regulation. In fact, mutations in TACI, one of the three BLyS receptors, are associated with CVID. Based on these facts, we hypothesized that BLyS could be a candidate gene for CVID. We screened 78 patients with CVID using DHPLC and direct sequencing: No disease causing mutations were identified. A novel heterozygous single nucleotide polymorphism (SNP) was found in exon 1 of one individual, however this SNP (G189A) does not lead to an amino acid substitution.
