Sound velocity measurements in dense glass bead packs reveal significant softening effect at large amplitudes, due to the frictional nonlinearity at the grain contacts. Beyond a certain amplitude, the sound-matter interaction becomes irreversible, leaving the medium in a weakened and slightly compacted state. A slow recovery of the initial elastic modulus is observed after acoustic perturbation, revealing the plastic creep growth of microcontacts. The cross-correlation function of configuration-specific acoustic speckles highlights the relationship between the macroscopic elastic weakening and the local change of the contact networks, induced by strong sound vibration, in the absence of appreciable grain motion.

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Basophils express not only high-affinity IgE receptors, but also low-affinity IgG receptors. Which, among these receptors, are expressed by human basophils is poorly known. Low-affinity IgG receptors comprise CD32 (FcγRIIA, FcγRIIB, and FcγRIIC) and CD16 (FcγRIIIA and FcγRIIIB). FcγRIIA, FcγRIIC, and FcγRIIIA are activating receptors, FcγRIIB are inhibitory receptors, FcγRIIIB are GPI-anchored receptors whose function is poorly understood. Basophils were reported to express FcγRII, but not FcγRIII. We aimed at further identifying basophil IgG receptors. Basophils from normal donors and from patients suffering from an allergic skin disease (atopic dermatitis), allergic respiratory diseases (allergic rhinitis and asthma), or a nonallergic skin disease (chronic urticaria) were examined. We found that normal basophils contain FcγRIII transcripts and express FcγRIIIB, but not FcγRIIIA, which were detected on 24–81% basophils from normal donors and on 12–100% basophils from patients. Noticeably, the proportion of FcγRIIIB+ basophils was significantly lower in atopic dermatitis patients than in other subjects. This decreased FcγRIII expression was not correlated with an activated phenotype of basophils in atopic dermatitis patients, although FcγRIIIB expression was down-regulated upon basophil activation by anti-IgE. Our results challenge the two dogmas 1) that basophils do not express FcγRIII and 2) that FcγRIIIB is exclusively expressed by neutrophils. They suggest that a proportion of basophils may be lost during enrichment procedures in which FcγRIII+ cells are discarded by negative sorting using anti-CD16 Abs. They unravel an unexpected complexity of IgG receptors susceptible to modulate basophil activation. They identify a novel systemic alteration in atopic dermatitis.

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