Chronic follicular bronchiolitis requires antigen-specific regulatory T cell control to prevent fatal disease progression

A human STAT3 gain-of-function variant confers T cell dysregulation without predominant Treg dysfunction in mice

Primary immune regulatory disorders (PIRD) represent a group of disorders characterized by immune dysregulation, presenting with a wide range of clinical disease, including autoimmunity, autoinflammation, or lymphoproliferation. Autosomal dominant germline gain-of-function (GOF) variants in STAT3 result in a PIRD with a broad clinical spectrum. Studies in patients have documented a decreased frequency of FOXP3+ Tregs and an increased frequency of Th17 cells in some patients with active disease. However, the mechanisms of disease pathogenesis in STAT3 GOF syndrome remain largely unknown, and treatment is challenging. We developed a knock-in mouse model harboring a de novo pathogenic human STAT3 variant (p.G421R) and found these mice developed T cell dysregulation, lymphoproliferation, and CD4+ Th1 cell skewing. Surprisingly, Treg numbers, phenotype, and function remained largely intact; however, mice had a selective deficiency in the generation of iTregs. In parallel, we performed single-cell RNA-Seq on T cells from STAT3 GOF patients. We demonstrate only minor changes in the Treg transcriptional signature and an expanded, effector CD8+ T cell population. Together, these findings suggest that Tregs are not the primary driver of disease and highlight the importance of preclinical models in the study of disease mechanisms in rare PIRD.

Small Airway Disease: A Step Closer to Etiology-Based Classification of Bronchiolitis

Three major histologic patterns of bronchiolitis: obliterative bronchiolitis, follicular bronchiolitis, and diffuse panbronchiolitis, are reviewed in detail. These distinct patterns of primary bronchiolar injury provide a useful starting point for formulating a differential diagnosis and considering possible causes. In support of the aim toward a cause-based classification system of small airway disease, a simple diagnostic algorithm is provided for further subclassification of the above 3 bronchiolitis patterns according to the major associated etiologic subgroups.

A model of TH17-associated ileal hyperplasia that requires both IL-17A and IFNγ to generate self-tolerance and prevent colitis

Homeostasis in the ileum, which is commonly disrupted in patients with Crohn's disease, involves ongoing immune responses. To study how homeostatic processes of the ileum impact CD4⁺T cell responses, we used TCR transgenic tools to breed mice that spontaneously produced CD4⁺T cells reactive to an antigen expressed in the ileum. At an early age, the ilea of these mice exhibit crypt hyperplasia and accumulate increased numbers of T_H17 cells bearing non-transgenic clonotypes. Half of these mice subsequently developed colitis linked to broad mucosal infiltration by T_H17 and T_H1 cells expressing non-transgenic clonotypes, chronic wasting disease and loss of ileal crypt hyperplasia. By contrast, adult mice with normal growth continued to exhibit T_H17-associated ileal crypt hyperplasia and additionally accumulated ileal-reactive Treg cells. Both IL-17A and IFNγ were protective, as their deficiency precluded ileal-reactive Treg accumulation and exacerbated colitic disease. IL-23R blockade prevented progression to colitis, whereas nTreg cell transfers prevented colitic disease, ileal crypt hyperplasia and ileal-reactive Treg accumulation. Thus, our studies identify an IL-17A and IFNγ-dependent homeostatic process that mobilizes ileal-reactive Treg cells and is disrupted by IL-23.

The Clinical Characteristics and Outcomes of Follicular Bronchiolitis in Chinese Adult Patients

Follicular bronchiolitis (FB) is a rare interstitial lung disease (ILD) and has been reported in diverse clinical contexts. Six FB patients demonstrated by surgical lung biopsy (SLB) were reviewed between 2009 and 2017 from Nanjing Drum Tower Hospital in China. The average age of subjects was 42 years old (range: 31-55 years). The clinical symptoms were very mild. The laboratory findings showed elevated Erythrocyte sedimentation rate (ESR) and serum globulin and anemia. Pulmonary function tests were normal in four cases. Five cases had underlying diseases, such as, Sjo¨gren's syndrome, multi-centric castlemans' disease, idiopathic pneumonia with autoimmune features and abscess. Five cases presented as interstitial lung disease (ILD) on chest imaging with centrilobular or peribronchiolar nodules, ground glass opacities, interlobular septal thickening, cysts and bronchiectasis. Isolated mass was in one patient. The histopathology suggested the changes of FB in all subjects. Prednisone and/or cyclophosphamide were used in four cases, one did the surgery and the other was clinically monitored. All cases were alive at the end of follow up. The adult patients of FB usually have mild symptoms, ILD and underlying diseases. The definite diagnosis needs SLB. The prognosis is depended on their underlying conditions.