Our objective was to establish an experimental model of a self-sustained and bistable extracellul... more Our objective was to establish an experimental model of a self-sustained and bistable extracellular signal-regulated kinase 1/2 (ERK1/2) signaling process. A single stimulation of cells with cytokines causes rapid ERK1/2 activation, which returns to baseline in 4 h. Repeated stimulation leads to sustained activation of ERK1/2 but not Jun N-terminal protein kinase (JNK), p38, or STAT6. The ERK1/2 activation lasts for 3 to 7 days and depends upon a positive-feedback mechanism involving Sprouty 2. Overexpression of Sprouty 2 induces, and its genetic deletion abrogates, ERK1/2 bistability. Sprouty 2 directly activates Fyn kinase, which then induces ERK1/2 activation. A genome-wide microarray analysis shows that the bistable phospho-ERK1/2 (pERK1/2) does not induce a high level of gene transcription. This is due to its nuclear exclusion and compartmentalization to Rab5+ endosomes. Cells with sustained endosomal pERK1/2 manifest resistance against growth factor withdrawal-induced cell dea...
Interleukin 5 (IL-5) regulates the growth and function of eosinophils. The objective of this stud... more Interleukin 5 (IL-5) regulates the growth and function of eosinophils. The objective of this study was to investigate the intracellular signal transduction mechanism of IL-5 in eosinophils. Purified eosinophils were stimulated with IL-5, and the involvement of various kinases was investigated by immunoblotting, immune complex kinase assay, and in situ denatured/renatured kinase assay. We found that IL-5 induced tyrosine phosphorylation and activation of a number of kinases. Two species of lyn kinases (53 and 56 kD) were present in eosinophils. Both forms were Tyr-phosphorylated and activated rapidly within 1 min. Further, lyn kinase was physically associated with the IL-5 beta receptor in eosinophils. Ras was studied by immunoprecipitation followed by thin-layer chromatography. Ras bound higher quantities of [alpha-32P]guanosine 5'triphosphate upon stimulation with IL-5. Raf-1 kinase showed increased Tyr phosphorylation on immunoblotting and increased activity in the immune comp...
Allergen-specific immunotherapy modulates the balance of circulating Tfh and Tfr cells
The Journal of allergy and clinical immunology, Jan 12, 2017
Follicular helper T cells (Tfh cells) are a CD4 T cell subset essential for germinal center forma... more Follicular helper T cells (Tfh cells) are a CD4 T cell subset essential for germinal center formation and B cell responses, although their role in allergy and allergen-specific immunotherapy (AIT) is unclear. Here, we show that AIT-treated patients have a higher ratio of regulatory Tfh cells (Tfr) to follicular T cells (Tfh) and hypothesize an IL-2 dependent mechanism.
Background: Aspirin desensitization provides long-term clinical benefits. The exact mechanisms of... more Background: Aspirin desensitization provides long-term clinical benefits. The exact mechanisms of aspirin desensitization are not clearly understood. Objective: We sought to evaluate the effects of nonsteroidal anti-inflammatory drugs (NSAIDs) on T-cell activation of the IL-4 pathway in aspirin-sensitive patients with asthma and control subjects. Methods: A total of 11 aspirin-sensitive patients with asthma, 10 aspirin-tolerant patients with asthma, and 10 controls without asthma were studied. PBMCs were stimulated with an anti-CD3 antibody and IL-4 or IL-12, with and without the presence of NSAIDs. The expression of phosphorylated signal transducers and activators of transcription 6 (pSTAT6), phosphorylated signal transducers and activators of transcription 4, and IL-4 was detected in CD4 T cells by flow cytometry. Results: Stimulation with a combination of anti-CD3 and IL-4 induced pSTAT6 in CD4 T cells from all subjects. The induction of pSTAT6 was significantly higher in aspirin-sensitive patients with asthma than in controls subjects. The increase in pSTAT6 was inhibited in a dose-dependent manner by aspirin and indomethacin and minimally by sodium salicylate. This inhibition was strongest in aspirin-sensitive patients. Two-group comparisons showed significant differences in pSTAT6 inhibition by all concentrations of indomethacin and aspirin: between aspirin-sensitive and aspirin-tolerant groups and between aspirin-sensitive and control groups. No differences were found between aspirin-tolerant and control groups at all 3 concentrations. The inhibition of pSTAT6 was associated with reduced IL-4 expression. Conclusions: NSAIDs inhibited signal transducers and activators of transcription 6 signaling in CD4 T cells. This inhibition was significantly higher in aspirin-sensitive patients than in aspirintolerant subjects and was associated with reduced expression of IL-4. These findings have implications for clinical benefits of aspirin desensitization in aspirin-sensitive patients with asthma.
Respiratory syncytial virus (RSV) is the major cause of acute bronchiolitis in infancy, a syndrom... more Respiratory syncytial virus (RSV) is the major cause of acute bronchiolitis in infancy, a syndrome characterized by wheezing, respiratory distress, and the pathologic findings of peribronchial mononuclear cell infiltration and release of inflammatory mediators by basophil and eosinophil leukocytes. Composition and activation of this cellular response are thought to rely on the discrete target cell selectivity of CC chemokines. We demonstrate that infection in vitro of human epithelial cells of the lower respiratory tract by RSV induced doseand time-dependent increases in mRNA and protein secretion for RANTES (regulated upon activation, normal T-cell expressed and presumably secreted), monocyte chemotactic protein-1 (MCP-1), and macrophage inflammatory protein-1␣ (MIP-1␣). Production of MCP-1 and MIP-1␣ was selectively localized only in epithelial cells of the small airways and lung. Exposure of epithelial cells to gamma interferon (IFN-␥), in combination with RSV infection, induced a significant increase in RANTES production that was synergistic with respect to that obtained by RSV infection or IFN-␥ treatment alone. Epithelial cell-derived chemokines exhibited a strong chemotactic activity for normal human blood eosinophils. Furthermore, eosinophils were susceptible to RSV and released RANTES and MIP-1␣ as a result of infection. Therefore, the inflammatory process in RSV-induced bronchiolitis appears to be triggered by the infection of epithelial cells and further amplified via mechanisms driven by IFN-␥ and by the secretion of eosinophil chemokines.
Data Revues 00916749 V131i2ss S0091674912033970, Jan 26, 2013
RATIONALE: Regulation of allergic inflammation has been largely attributed to regulatory T cells.... more RATIONALE: Regulation of allergic inflammation has been largely attributed to regulatory T cells. IL-10+ B cells have immunomodulatory properties and have been shown to be altered in autoimmune diseases. We hypothesised that IL-10+ B cells were also dysregulated in grass pollen allergic individuals. METHODS: Grass pollen allergic rhinitics (AR) and non-atopic (NA) controls were studied. PBMCs or negatively selected CD19+ B cells were cultured with CpG [1ug/mL]. Frequencies of IL-10+ B cells were quantified by FluoroSpot assay. IL-10+ B cells were phenotyped by flow cytometry. Suppression of allergen-driven CFSE-labelled CD4+ T cell proliferation was assessed in the presence of CpG-primed or un-primed B cells. RESULTS: CpG-stimulation of CD19+ B cells resulted in greater proportions of IL-10+ cells compared with medium alone (n513;p<0.001). Increased proportions of IL-10+ B cells were observed within CD5+ (p50.009), CD24hiCD38hi (p50.001), CD10+ (p50.004) and PD-L1+ (p<0.001) B cell subsets. Co-culture of CpG-primed B cells (1:1 with CD4+ T cells for 9 days) resulted in suppression of allergenstimulated CD4+ T cell proliferation (p50.03). This suppression was not reversed by the addition of anti-IL-10 (p50.02), anti-IL-10R (p50.003) or anti-TGF-beta (p50.04) neutralising antibodies. Frequencies and proportions of IL-10+ B cells were reduced in AR compared to NA as measured by both FluoroSpot (p50.04) and flow cytometry(p50.03). CONCLUSIONS: IL-10+ regulatory B cells suppressed allergen-driven T cell proliferation. The suppression was not IL-10 or TGF-beta dependent. Grass pollen allergic individuals have lower proportions of IL-10+ B cells relative to non-atopic controls. Whether this cell type contributes to efficacy and tolerance after immunotherapy remains to be tested. J ALLERGY CLIN IMMUNOL FEBRUARY 2013 AB204 Abstracts MONDAY
Data Revues 00916749 V125i2ss1 S009167490901985x, Aug 13, 2011
Background. Despite vernal keratoconjunctivitis is included in ocular allergies, the role of alle... more Background. Despite vernal keratoconjunctivitis is included in ocular allergies, the role of allergy in the pathogenesis of the disease is still unclear. Due to the strict relationship between the eye and the nose in respiratory allergy, we attempted to assess the involvement of the nasal mucosa in VKC.
Uploads
Papers by Rafeul Alam