Novel peanut-specific human IgE monoclonal antibodies enable screens for inhibitors of the effector phase in food allergy.

Background: 10% of US residents have food allergies, including 2% with peanut allergy. Mast cell mediators released during the allergy effector phase drive allergic reactions. Therefore, targeting sensitized mast cells may prevent food allergy symptoms. Objective: We used novel, human, allergen-specific, IgE monoclonal antibodies (mAbs) created using human hybridoma techniques to design an in vitro system to evaluate potential therapeutics targeting sensitized effector cells. Methods: Two human IgE mAbs specific for peanut, generated through human hybridoma techniques, were used to sensitize rat basophilic leukemia (RBL) SX-38 cells expressing the human IgE receptor (FcϵRI). Beta-hexosaminidase release (a marker of degranulation), cytokine production, and phosphorylation of signal transduction proteins downstream of FcϵRI were measured after stimulation with peanut. Degranulation was also measured after engaging inhibitory receptors CD300a and Siglec-8. Results: Peanut-specific human IgE mAbs bound FcϵRI, triggering degranulation after stimulation with peanut in RBL SX-38 cells. Sensitized RBL SX-38 cells stimulated with peanut increased levels of phosphorylated SYK and ERK, signal transduction proteins downstream of FcϵRI. Engaging inhibitory cell surface receptors CD300a or Siglec-8 blunted peanut-specific activation. Conclusion: Allergen-specific human IgE mAbs, expressed from human hybridomas and specific for a clinically relevant food allergen, passively sensitize allergy effector cells central to the in vitro models of the effector phase of food allergy. Peanut reproducibly activates and induces degranulation of RBL SX-38 cells sensitized with peanut-specific human IgE mAbs. This system provides a unique screening tool to assess the efficacy of therapeutics that target allergy effector cells and inhibit food allergen-induced effector cell activation.

Anaphylaxis.

Anaphylaxis is a systemic, life-threatening disorder triggered by mediators released by mast cells and basophils activated via allergic (IgE-mediated) or nonallergic (non-IgE-mediated) mechanisms. It is a rapidly evolving, multisystem process involving the integumentary, pulmonary, gastrointestinal, and cardiovascular systems. Anaphylaxis and angioedema are serious disorders that can lead to fatal airway obstruction and culminate in cardiorespiratory arrest, resulting in hypoxemia and/or shock. Often, these disorders can be appropriately managed in an outpatient setting; however, these conditions can be severe enough to warrant evaluation of the patient in the ED and in some cases, hospitalization, and management in an ICU. Reports suggest that underdiagnosis and undertreatment of anaphylaxis are common. Several new syndromes have been described recently including bird-egg, pork-cat, delayed allergy to mammalian meat and a diverse group of mast cell activation disorders. Conditions such as postural orthostatic tachycardia syndrome, carcinoid syndrome, Munchausen stridor, and factitious anaphylaxis can present similarly and need to be included in the differential diagnosis. Anaphylaxis is a clinical diagnosis, but plasma tryptase and urinary histamine levels are often elevated, allowing diagnostic confirmation; however, diagnostic testing should not delay treatment as results may not be immediately available. The sine qua non of treatment is avoidance of any known triggers and epinephrine, which should never be delayed if this disorder is suspected. Secondary treatments include fluids, bronchodilators, antihistamines, and glucocorticoids. Patients with cardiopulmonary arrest or airway or vascular compromise require mechanical ventilation, vasopressors, and other advanced life support in the ICU.

Toll-like receptor 4-mediated regulation of spontaneous Helicobacter-dependent colitis in IL-10-deficient mice.

BACKGROUND & AIMS: The commensal microbiota is believed to have an important role in regulating immune responsiveness and preventing intestinal inflammation. Intestinal microbes produce signals that regulate inflammation via Toll-like receptor (TLR) signaling, but the mechanisms of this process are poorly understood. We investigated the role of the anti-inflammatory cytokine interleukin (IL)-10 in this signaling pathway using a mouse model of colitis. METHODS: Clinical, histopathologic, and functional parameters of intestinal inflammation were evaluated in TLR4(-/-), IL-10(-/-), and TLR4(-/-) x IL-10(-/-) mice that were free of specific pathogens and in TLR4(-/-) x IL-10(-/-) mice following eradication and reintroduction of Helicobacter hepaticus. Regulatory T-cell (Treg) function was evaluated by crossing each of the lines with transgenic mice that express green fluorescent protein under control of the endogenous regulatory elements of Foxp3. Apoptotic cells in the colonic lamina propria were detected by a TUNEL assay. RESULTS: TLR4-mediated signals have 2 interrelated roles in promoting inflammation in TLR4(-/-) x IL-10(-/-) mice. In the absence of TLR4-mediated signals, secretion of proinflammatory and immunoregulatory cytokines is dysregulated. Tregs (Foxp3(+)) that secrete interferon-gamma and IL-17 accumulate in the colonic lamina propria of TLR4(-/-) x IL-10(-/-) mice and do not prevent inflammation. Aberrant control of epithelial cell turnover results in the persistence of antigen-presenting cells that contain apoptotic epithelial fragments in the colonic lamina propria of Helicobacter-infected TLR4(-/-) mice. CONCLUSIONS: In mice that lack both IL-10- and TLR4-mediated signals, aberrant regulatory T-cell function and dysregulated control of epithelial homeostasis combine to exacerbate intestinal inflammation.

HIV diagnostic tests: an overview.

This article provides an overview of different HIV diagnostic tests, describing how they work and the advantages and limitations of the various tests. This article also briefly reviews the structure and genetic diversity of HIV, the mechanism the virus uses to infect host cells and the different phases of HIV infection. This information is included to facilitate understanding of how HIV diagnostic tests work and what molecular markers these tests use to pinpoint an HIV infection.