PubMed Health⌕ Search

Biomedical subjects

Sarbjit Saini

Publications and source records attributed to Sarbjit Saini.

5 recordsLinked to original sources
PubMed2005

TLR9- and FcepsilonRI-mediated responses oppose one another in plasmacytoid dendritic cells by down-regulating receptor expression.

Plasmacytoid dendritic cells (pDC) express not only TLR9 molecules through which ligation with CpG DNA favors Th1 responses but also possess IgE receptors (FcepsilonRI) implicated in allergen presentation and induction of Th2 responses. This dichotomy prompted an investigation to determine whether TLR9- and IgE receptor-mediated responses oppose one another in pDC by affecting receptor expression and associated functional responses. Results showed that IgE cross-linking reduced TLR9 in pDC and inhibited the capacity of these cells to secrete IFN-alpha when stimulated with the CpG oligodeoxynucleotide (ODN)-2216. In contrast, an approximately 15-fold reduction in FcepsilonRIalpha mRNA and a loss in surface protein were seen in pDC first exposed to TLR9 ligation with ODN-2216. Results indicated that type I IFNs partly mediated this effect, as rIFN-alpha also caused a significant approximately 4-fold reduction in FcepsilonRIalpha mRNA. Finally, this reduction in FcepsilonRIalpha mediated by ODN-2216 correlated with a selective suppression of allergen-induced CD4+ T cell proliferation, but not of responses resulting from tetanus toxoid. Overall, these results imply mechanisms by which specific innate and IgE-dependent immune responses counterregulate one another at the dendritic cell level and may have significant impact on whether an ensuing response is either of Th1 or Th2 in nature.

Adult↗
PubMed2004

Systemic effects of allergen exposure on blood basophil IL-13 secretion and FcepsilonRIbeta.

BACKGROUND: Airway allergen challenge studies have shown the upregulation of cytokines in local airway tissues and distal effects on bone marrow precursors for eosinophils and basophils. OBJECTIVE: We investigated whether local intranasal allergen challenge alters the phenotype of circulating basophils to a primed state. METHODS: Ten subjects with allergic rhinitis were challenged with allergen by means of intranasal spray on 3 sequential days. Basophils were isolated from subjects before challenge and 3, 24, and 96 hours after the third allergen challenge. Basophils were compared before challenge and after the last allergen challenge for levels of FcepsilonRIbeta protein by means of Western blotting and for FcepsilonRIbeta mRNA expression by means of real-time PCR. Basophils were also compared with regard to spontaneous secretion of IL-4 and IL-13. RESULTS: Basophil FcepsilonRIbeta protein levels increased in 5 of 6 subjects after allergen challenge relative to before challenge. Likewise, basophil FcepsilonRIbeta mRNA levels increased a median of 2-fold after the last challenge relative to before challenge ( P=.007, n=9). IL-13 protein was detected in supernatants of 7 of 9 subjects' basophil-enriched cultures after the last challenge compared with 3 of 9 basophil-enriched cultures before challenge (median, 6.2 vs 0 pg/mL; P=.058). IL-4 was not detected in any culture supernatant. CONCLUSION: Intranasal allergen challenge transiently activates circulating basophils by increasing expression of the FcepsilonRIbeta subunit and spontaneous IL-13 secretion. Because FcepsilonRIbeta is an amplifier of FcepsilonRI-mediated responses and IL-13 is proinflammatory, these findings support a primed basophil functional state and demonstrate a systemic effect of local allergen challenge that could contribute in exacerbating allergic reactions.

Administration, Intranasal↗
PubMed2004

Omalizumab-induced reductions in mast cell Fce psilon RI expression and function.

BACKGROUND: By design, omalizumab binds free IgE in the circulation and prevents its attachment to the surface of mast cells and basophils, thereby preventing them from responding to allergens. Previously, omalizumab rapidly reduced free IgE levels, as well as basophil high-affinity IgE receptors, leading to significant reductions in basophil mediator response to allergen. It is assumed that tissue mast cells are similarly altered in their Fc epsilon RI density and function. OBJECTIVE: We examined the phenotypic shift of skin mast cells in parallel to that of blood basophils in 3 subjects infused with omalizumab. METHODS: Three subjects with allergic rhinitis underwent intradermal skin test titration with house dust mite antigen at days 0, 7, 70, and 196 of omalizumab treatment. As control subjects, 5 untreated subjects with allergic rhinitis were evaluated at similar time points. All subjects underwent skin biopsy 18 to 24 hours later at the site of allergen injection. Biopsy specimens were characterized by means of immunohistochemisty for tryptase and Fc epsilon RI alpha immunoreactivity, as well other markers (CD3, CD45RO, CD68, cutaneous lymphocyte antigen, and major basic protein). RESULTS: Omalizumab recipients, but not control subjects, demonstrated reductions in Fc epsilon RI alpha immunoreactivity at days 70 and 196 in parallel with reductions in the acute wheal response to allergen. However, no reductions in tryptase-positive cells were noted at these time points. CONCLUSION: Reductions in free IgE levels by omalizumab leads to a rapid reduction in basophil Fc epsilon RI receptor expression. In contrast, the time course for the decrease of Fc epsilon RI expression in skin mast cells is slower and associated with decreased acute allergen wheal size.

Allergens↗