The extracellular antagonists of the Wnt signalling pathway can be divided into two broad classes. Both classes of molecule prevent ligand-receptor interactions, but by different mechanisms: members of the first class, which include the sFRP (secreted Frizzled-related protein) family, WIF (Wnt inhibitory factor)-1 and Cerberus, primarily bind to Wnt proteins; the second class comprises certain members of the Dickkopf (Dkk) family, which bind to one subunit of the Wnt receptor complex. In addition, there are other protein interactions that contribute to Wnt antagonist function. Moreover, certain sFRPs and Dkks do not antagonise Wnt function, which suggests that these families have as-yet-undiscovered functions.

Anaphylaxis is an acute, severe, and potentially fatal systemic allergic reaction. Immunoglobulin E (IgE), mast cells, and histamine have long been associated with anaphylaxis, but an alternative pathway mediated by IgG has been suggested to be more important in the elicitation of anaphylaxis. Here, we showed that basophils, the least common blood cells, were dispensable for IgE-mediated anaphylaxis but played a critical role in IgG-mediated, passive and active systemic anaphylaxis in mice. In vivo depletion of basophils but not macrophages, neutrophils, or NK cells ameliorated IgG-mediated passive anaphylaxis and rescued mice from death in active anaphylaxis. Upon capture of IgG-allergen complexes, basophils released platelet-activating factor (PAF), leading to increased vascular permeability. These results highlight a pivotal role for basophils in vivo and contrast two major, distinct pathways leading to allergen-induced systemic anaphylaxis: one mediated by basophils, IgG, and PAF and the other "classical" pathway mediated by mast cells, IgE, and histamine.

Ticks are ectoparasitic arthropods that can transmit a variety of microorganisms to humans and animals during blood feeding, causing serious infectious disorders, including Lyme disease. Acaricides are pharmacologic agents that kill ticks. The emergence of acaricide-resistant ticks calls for alternative control strategies for ticks and tick-borne diseases. Many animals develop resistance to ticks after repeated infestations, but the nature of this acquired anti-tick immunity remains poorly understood. Here we investigated the cellular and molecular mechanisms underlying acquired resistance to Haemaphysalis longicornis ticks in mice and found that antibodies were required, as was IgFc receptor expression on basophils but not on mast cells. The infiltration of basophils at tick-feeding sites occurred during the second, but not the first, tick infestation. To assess the requirement for basophil infiltration to acquired tick resistance, mice expressing the human diphtheria toxin receptor under the control of the mast cell protease 8 (Mcpt8) promoter were generated. Diphtheria toxin administration to these mice selectively ablated basophils. Diphtheria toxin-mediated basophil depletion before the second tick infestation resulted in loss of acquired tick resistance. These data provide the first clear evidence, to our knowledge, that basophils play an essential and nonredundant role in antibody-mediated acquired immunity against ticks, which may suggest new strategies for controlling tick-borne diseases.

Opticospinal multiple sclerosis (OSMS) in Asians has similar features to the relapsing-remitting form of neuromyelitis optica (NMO) seen in Westerners. OSMS is suggested to be NMO based on the frequent detection of specific IgG targeting aquaporin-4 (AQP4), designated NMO-IgG. The present study sought to clarify the significance of anti-AQP4 autoimmunity in the whole spectrum of MS. Sera from 113 consecutive Japanese patients with clinically definite MS, based on the Poser criteria, were assayed for anti-AQP4 antibodies by immunofluorescence using GFP-AQP4 fusion protein-transfected HEK-293T cells. Sensitivity and specificity of the anti-AQP4 antibody assay, 83.3 and 100%, respectively, were calculated using serum samples with NMO-IgG status predetermined at the Mayo Clinic. The anti-AQP4 antibody positivity rate was significantly higher in OSMS patients (13/48, 27.1%) than those with CMS (3/54, 5.6%), other neurological diseases (0/52) or healthy controls (0/35). None of the 11 patients tested with a brainstem-spinal form of MS were positive. Among OSMS patients, the antibody positivity rate was highest in OSMS patients with longitudinally extensive spinal cord lesions (LESCLs) extending over three vertebral segments and brain lesions that fulfilled the Barkhof criteria (5/9, 55.6%). Multiple logistic analyses revealed that emergence of the anti-AQP4 antibody was positively associated only with a higher relapse rate, but not with optic-spinal presentation or LESCLs. Compared with anti-AQP4 antibody-negative CMS patients, anti-AQP4 antibody-positive MS patients showed significantly higher frequencies of severe optic neuritis, acute transverse myelitis and LESCLs while most conditions were also common to anti-AQP4 antibody-negative OSMS patients. The LESCLs in anti-AQP4 antibody-positive patients were located at the upper-to-middle thoracic cord, while those in anti-AQP4 antibody-negative OSMS patients appeared throughout the cervical-to-thoracic cord. On axial planes, the former most frequently showed central grey matter involvement, while holocord involvement was predominant in the latter. In contrast, LESCLs in anti-AQP4 antibody-negative CMS patients preferentially involved the mid-cervical cord presenting a peripheral white matter-predominant pattern, as seen in the short lesions. Anti-AQP4 antibody-positive MS patients fulfilling definite NMO criteria showed female preponderance, higher relapse rate, greater frequency of brain lesions and less frequent responses to interferon beta-1b than anti-AQP4 antibody-negative OSMS patients with LESCLs. These findings suggested that LESCLs are distinct in anti-AQP4 antibody positivity and clinical phenotypes. There were cases of anti-AQP4 antibody-positive MS/NMO distinct from CMS, and anti-AQP4 antibody-negative OSMS with LESCLs in Japanese. This indicated that the mechanisms producing LESCLs are also heterogeneous in cases with optic-spinal presentation, namely AQP4 autoimmunity-related and -unrelated.

CD44 is a widely distributed cell surface adhesion molecule and is implicated in diverse biological processes. However, the nature of intracellular signaling triggered by CD44 remains to be elucidated. Here, we show that CD44 undergoes sequential proteolytic cleavage in the ectodomain and intracellular domain, resulting in the release of a CD44 intracellular domain (ICD) fragment. Consequently, CD44ICD acts as a signal transduction molecule, where it translocates to the nucleus and activates transcription mediated through the 12-O-tetradecanoylphorbol 13-acetate–responsive element, which is found in numerous genes involved in diverse cellular processes. Expression of an uncleavable CD44 mutant as well as metalloprotease inhibitor treatment blocks CD44-mediated transcriptional activation. In search of the underlying mechanism, we have found that CD44ICD potentiates transactivation mediated by the transcriptional coactivator CBP/p300. Furthermore, we show that cells expressing CD44ICD produce high levels of CD44 messenger RNA, suggesting that the CD44 gene is one of the potential targets for transcriptional activation by CD44ICD. These observations establish a novel CD44 signaling pathway and shed new light on the functional link between proteolytic processing of an adhesion molecule at the cell surface and transcriptional activation in the nucleus.