Are dysregulated inflammatory responses to commensal bacteria involved in the pathogenesis of hepatobiliary-pancreatic autoimmune disease? An analysis using mice models of primary biliary cirrhosis and autoimmune pancreatitis

Mechanistic Insights into Autoimmune Pancreatitis and IgG4-Related Disease

Autoimmune pancreatitis (AIP) is a pancreatic manifestation of a recently defined disease form known as IgG4-related disease (AIP/IgG4-RD). AIP/IgG4-RD is characterized by elevated systemic IgG4 antibody concentrations and lesional tissues infiltrated by IgG4-expressing plasmacytes. In addition, recent studies have revealed that, in common with other autoimmune diseases, such as systemic lupus erythematosus (SLE) and psoriasis, AIP/IgG4-RD is associated with increased type I IFN (IFN-I) production by plasmacytoid dendritic cells (pDCs). However, unlike SLE, AIP/IgG4-RD is characterized by elevated IFN-I-dependent IL-33 production, the latter emerging as an important contributor to inflammation and fibrotic responses characterizing this disease. On this basis, we propose that blockade of the IFN-I/IL-33 axis might constitute a successful approach to treating this unique type of autoimmunity.

Prevalence and Clinicopathological Features of Triaditis in a Prospective Case Series of Symptomatic and Asymptomatic Cats

Background

The term triaditis designates the concurrent presence of idiopathic inflammatory bowel disease (IBD), cholangitis, and pancreatitis in cats.

Hypothesis/Objectives

The histopathology of concurrent, but often subclinical, inflammatory processes in the small intestine, liver, and pancreas of cats is poorly described. We aimed to investigate the frequency of enteritis, cholangitis, pancreatitis, or some combination of these in symptomatic and asymptomatic cats, compare clinicopathological features, and correlate histopathological with laboratory findings.

Animals

Domestic cats (27 symptomatic, 20 asymptomatic, and 8 normal).

Methods

Prospective study. Physical examination, laboratory variables (CBC, serum biochemistry profile, serum thyroxine concentration, serum feline trypsin‐like immunoreactivity [fTLI], feline lipase immunoreactivity [fPLI, as measured by Spec fPL^®], urinalysis, and fecal analysis), imaging, and histopathological examinations were conducted. Feline liver, pancreas, and small intestine were biopsied during laparotomy.

Results

Inflammatory lesions were detected in 47 cats (27 symptomatic, 20 asymptomatic). In total, 20 cats had histopathologic lesions of IBD (13/47, 27.7%), cholangitis (6/47, 12.8%), or pancreatitis (1/47, 2.1%) alone, or inflammation involving >1 organ (27/47, 57.4%). More specifically, 16/47 cats (34.0%) had concurrent lesions of IBD and cholangitis, 3/47 (6.4%) of IBD and pancreatitis, and 8/47 cats (17%) of triaditis. Triaditis was identified only in symptomatic cats (8/27, 29.6%). A mild, positive correlation was detected between the severity (score) of IBD lesions and the number of comorbidities (rho = +0.367, P = .022).

Conclusions and Clinical Importance

Histopathological evidence of IBD or IBD with comorbidities was detected in both symptomatic and asymptomatic cats. The possibility of triaditis should be considered in symptomatic cats with severe IBD.

Involvement of commensal bacteria may lead to dysregulated inflammatory and autoimmune responses in a mouse model for chronic nonsuppurative destructive cholangitis

BACKGROUND

We previously reported a mouse model of primary biliary cirrhosis (PBC)-like chronic nonsuppurative destructive cholangitis (CNSDC), in which frequent injections of Streptococcus intermedius induced CNSDC and autoantibody production. The present study was performed to verify the model by examining 1) the reappearance of the PBC-like CNSDC after lymphocyte transfer from model to naïve mice, 2) the involvement of autophagy, and 3) the influence of the strain difference.

METHODS

Mice were inoculated with S. intermedius weekly for 8 weeks, then sacrificed to obtain samples. Spleen cells obtained from S. intermedius-inoculated mice were transferred to RAG2(-/-) mice.

RESULTS

CNSDC and elevated serum level of anti-gp210 titers were observed in S. intermedius-inoculated C57BL/6 mice, similar to the results of our previous report using BALB/c mice. Portal inflammation was induced in the livers of RAG2(-/-) mice by the transfer of spleen cells from S. intermedius-inoculated C57BL/6 mice. Among the inflammatory cells in the RAG2(-/-) mice, CD3-positive cells were predominant. Autophagosome-like structures were detected histologically, in the cytoplasm of infiltrated cells around the bile ducts in the livers of S. intermedius-inoculated both C57BL/6 and BALB/c mice. In S. intermedius-inoculated C3H/HeJ mice, inflammation in the portal area was less extensive than that in the hepatic parenchyma.

CONCLUSION

Bacterial component(s) and sequentially upregulated innate and acquired immune responses, accompanied by autophagy, might trigger CNSDC, via autoimmune mechanisms. Throughout the generation of bacteria-triggered PBC-like CNSDC, strain difference may influence the response to S. intermedius-inoculation in the liver.

Commensal Flora, is it an Unwelcomed Companion as a Triggering Factor of Autoimmune Pancreatitis?

The etiopathogenesis of many autoimmune disorders has not been identified. The aim of this paper is to focus on the involvement of bacterial exposure, as an environmental factor, in the pathogenesis of autoimmune pancreatitis (AIP), which is broadly categorized as autoimmune disorders involving pancreatic lesions. Avirulent and/or commensal bacteria, which may have an important role(s) as initiating/progressing factors in the pathogenesis of autoimmune disorder AIP, will be emphasized.