B cells represent a key cellular component of humoral immunity. Besides antigen presentation and antibody production, B cells also play a role in immune regulation and induction of tolerance through several mechanisms. Our understanding of B-lineage cells with regulatory ability has been revolutionized by the delineation of heterogeneous subsets of these cells. Specific environmental signals may further determine the polarization and function of B-lineage regulatory cells. With the availability of new genetic, molecular and pharmacological tools, considerable advances have been made toward our understanding of the surface phenotype, developmental processes and functions of these cells. These exciting discoveries, some of which are still controversial, also raise many new questions, which makes the inhibitory function of B cells a rapidly growing field in immunopathology. Here we review highlights of the regulatory activity of B cells and the recent advances in the function and phenotype of these B-cell subsets in healthy and diseased states.

Purpose Similar to chronic obstructive pulmonary disease (COPD), the diffusing capacity of the lung (D LCO ) might be decreased and associated with poor prognosis in preserved ratio impaired spirometry (PRISm), a clinical entity as a prodromal phase of COPD. The aims of the present study were to evaluate the distributions of D LCO and to assess the association between D LCO and mortality among subjects with PRISm. Patients and Methods We conducted an observational cohort study at the National Hospital Organization Fukuoka National Hospital. We classified the 899 patients ≥ 40 years of age with an assessment of D LCO into five groups based on spirometry: preserved spirometry, PRISm, mild COPD, moderate COPD, and severe/very severe COPD. The prevalence of low D LCO (< 80% per predicted) was compared among the five groups. Using PRISm patients with follow-up data, we further investigated the association of low D LCO with all-cause mortality. Results The prevalence of low D LCO in the PRISm group (58.8%) was significantly higher than that in the preserved-spirometry group (21.8%), the mild-COPD group (23.5%), and the moderate-COPD group (36.0%) (all P < 0.01), and it was comparable to that in the severe/very severe-COPD group (63.2%). The results remained unchanged after adjusting for potential confounders. Among the PRISm subjects, the overall survival rate was significantly lower in the low-D LCO group than in the preserved-D LCO group ( P < 0.01). The multivariable-adjusted hazard ratio (HR) for all-cause mortality was significantly higher in the low-D LCO group than in the preserved-D LCO group (HR = 10.10 (95% confidence interval 2.33–43.89)). Conclusion Diffusing capacity was more impaired in PRISm subjects than in those with preserved spirometry or mild to moderate COPD. Regarding PRISm, low D LCO was a significant risk factor for all-cause mortality. Clinicians should assess D LCO in the management of PRISm to predict the future risk of overall death.

We describe the case of a 73-year-old man who experienced dry cough and exertional dyspnea after dabigatran administration. Chest radiographs revealed the development of bilateral consolidative and ground glass opacity, and transbronchial lung biopsy showed organized materials in the alveolar spaces with moderate inflammatory infiltrate and focal fibrosis. Lung opacity gradually disappeared after discontinuing dabigatran. To date, there has been only one report regarding dabigatran-induced lung injury, except for alveolar hemorrhage and eosinophilic pneumonia. Therefore, we should consider that any drug can cause various types of lung injuries.

Sarcoidosis is a systemic, granulomatous disease caused by unknown immunological abnormalities. The organs most vulnerable to sarcoidosis are the lungs. Patients often resolve spontaneously, but the lungs can also be severely affected. Although details regarding prognostic factors in sarcoidosis patients with lung involvement remain unclear, several reports have suggested that immune checkpoint molecules are involved in the pathogenesis of sarcoidosis. In this study, we divided sarcoidosis patients into two groups based on chest computed tomography (CT) findings and compared immune checkpoint molecules expressed on T cells in bronchoalveolar lavage fluid (BALF) in the two groups, using flow cytometry. We found elevated programmed cell death 1 (PD-1) or T cell immunoglobulin- and mucin-domain-containing molecule-3 (TIM-3) expression on T cells in BALF in patients with spontaneous improvement in CT findings, compared with those in patients without improvement in CT findings. In conclusion, our study implies that PD-1 or TIM-3 expression on T cells in BALF may be a prognostic factor for pulmonary lesions in sarcoidosis.

Recent studies have suggested an association between EB virus infection and IgG4-related diseases in the pathological exploration of surgically resected lymph nodes. Our case is the first case of IgG4-related lung disease in which EB virus infection was both pathologically and clinically proved. The present case is of particular interest in view of this newly reported association, and may serve as a fundamental report for future studies connecting EB virus infection with IgG4-related diseases.