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We evaluated the hypothesis that serum IgE regulates neutrophil FcεRI expression in the same manner as described for other FcεRI + cells. FcεRI expression by neutrophils of 40 asthma subjects and 20 control subjects did not correlate with serum IgE levels, whereas FcεRI expression by basophils of the same subjects showed a highly significant correlation. The level of FcεRI expression by neutrophils of both asthma and control subjects was approximately 1% of that for basophil FcεRI expression. IgE + neutrophils were minimally detectable, and FcεRI α subunit was not detected in Western blots of neutrophil membranes and cytosol. The neutrophil FcεRI did not support antiIgE stimulated superoxide release or IgE-induced increase in neutrophil survival. We conclude that FcεRI expression by neutrophils of both asthma patients and control individuals is minimal at best and that, if present, neutrophil FcεRI expression, unlike that of other human FcεRI + cells, is not regulated by serum IgE.

Recent studies on the urine microbiome have highlighted the importance of the gut–vagina–bladder axis in recurrent urinary tract infection (rUTI). In particular, the role of Gardnerella as a covert pathogen that activates E. coli in animal experiments has been reported. Herein, we conducted a human bladder microbiome study to investigate the effect of Gardnerella on rUTI. Urine 16S ribosomal RNA gene sequencing via transurethral catheterization was conducted in the normal control group (NC) (n = 18) and rUTI group (n = 78). The positive detection rate of Gardnerella species did not differ between the NC and rUTI groups (22.2% vs. 18.0%, p = 0.677). In addition, the Gardnerella-positive NC and Gardnerella-positive rUTI groups showed similar levels of microbiome diversity. The Gardnerella-positive group was categorized into three subgroups: the Escherichia-dominant group, Gardnerella-dominant group, and Lactobacillus-dominant group. All of the Escherichia-dominant groups were associated with rUTI. The Gardnerella-dominant or Lactobacillus-dominant groups expressed rUTI with symptoms when risk factors such as the degree of Gardnerella proliferation or causative agents of bacterial vaginosis were present. The presence of Gardnerella in the urine is considered to be related to rUTI depending on other risk factors. New guideline recommendations regarding antibiotic selection based on a novel method to detect the cause of rUTI may be required to reduce antibiotic resistance.

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