Gastric IgA in cystic fibrosis in relation to the migrating motor complex

Secretory Immunoglobulin A Immunity in Chronic Obstructive Respiratory Diseases

Chronic obstructive pulmonary disease (COPD), asthma and cystic fibrosis (CF) are distinct respiratory diseases that share features such as the obstruction of small airways and disease flare-ups that are called exacerbations and are often caused by infections. Along the airway epithelium, immunoglobulin (Ig) A contributes to first line mucosal protection against inhaled particles and pathogens. Dimeric IgA produced by mucosal plasma cells is transported towards the apical pole of airway epithelial cells by the polymeric Ig receptor (pIgR), where it is released as secretory IgA. Secretory IgA mediates immune exclusion and promotes the clearance of pathogens from the airway surface by inhibiting their adherence to the epithelium. In this review, we summarize the current knowledge regarding alterations of the IgA/pIgR system observed in those major obstructive airway diseases and discuss their implication for disease pathogenesis.

Immunoglobulin A Mucosal Immunity and Altered Respiratory Epithelium in Cystic Fibrosis

The respiratory epithelium represents the first chemical, immune, and physical barrier against inhaled noxious materials, particularly pathogens in cystic fibrosis. Local mucus thickening, altered mucociliary clearance, and reduced pH due to CFTR protein dysfunction favor bacterial overgrowth and excessive inflammation. We aimed in this review to summarize respiratory mucosal alterations within the epithelium and current knowledge on local immunity linked to immunoglobulin A in patients with cystic fibrosis.

Lung immunoglobulin A immunity dysregulation in cystic fibrosis

BACKGROUND

In cystic fibrosis (CF), recurrent infections suggest impaired mucosal immunity but whether production of secretory immunoglobulin A (S-IgA) is impaired remains elusive. S-IgA is generated following polymeric immunoglobulin receptor (pIgR)-mediated transepithelial transport of dimeric (d-)IgA and represents a major defence through neutralisation of inhaled pathogens like Pseudomonas aeruginosa (Pa).

METHODS

Human lung tissue (n = 74), human sputum (n = 118), primary human bronchial epithelial cells (HBEC) (cultured in air-liquid interface) (n = 19) and mouse lung tissue and bronchoalveolar lavage were studied for pIgR expression, IgA secretion and regulation.

FINDINGS

Increased epithelial pIgR immunostaining was observed in CF lung explants, associated with more IgA-producing plasma cells, sputum and serum IgA, especially Pa-specific IgA. In contrast, pIgR and IgA transport were downregulated in F508del mice, CFTR-inhibited HBEC, and CF HBEC. Moreover, the unfolded protein response (UPR) due to F508del mutation, inhibited IgA transport in Calu-3 cells. Conversely, pIgR expression and IgA secretion were strongly upregulated following Pa lung infection in control and F508del mice, through an inflammatory host response involving interleukin-17.

INTERPRETATION

A complex regulation of IgA secretion occurs in the CF lung, UPR induced by CFTR mutation/dysfunction inhibiting d-IgA transcytosis, and Pa infection unexpectedly unleashing this secretory defence mechanism.

FUNDING

This work was supported by the Forton's grant of the King Baudouin's Foundation, Belgium, the Fondazione Ricerca Fibrosi Cistica, Italy, and the Fonds National de la Recherche Scientifique, Belgium.

Gastrointestinal transit times and motility in patients with cystic fibrosis

OBJECTIVE

Patients with cystic fibrosis (CF) often suffer from gastrointestinal (GI) dysfunction including obstructive symptoms, malabsorption and pain, but the underlying pathophysiology remains obscure.

AIM

To compare GI motility and transit times in CF patients and healthy controls.

MATERIAL AND METHODS

Ten CF patients (five women, median age 23) with pancreatic insufficiency were studied. Total gastrointestinal transit time (GITT) and segmental colonic transit times (SCTT) were assessed by radiopaque markers. Gastric emptying and small intestinal transit were evaluated using the magnet-based motility tracking system (MTS-1). With each method patients were compared with 16 healthy controls.

RESULTS

Basic contraction frequencies of the stomach and small intestine were normal, but the pill reached the cecum after 7 h in only 20% of CF patients while in 88% of controls (p = 0.001). Paradoxically, velocity of the magnetic pill through the upper small intestine tended to be faster in CF patients (median 1.1 cm/min, range 0.7-1.7) compared with controls (median 1.0 cm/min, range 0.6-1.7) (p = 0.09). No statistically significant differences were found in median gastric emptying time (CF: 58 min, range 6-107 vs. healthy: 41 min, range 4-125 (p = 0.24)), GITT (CF: 2 days, range 0.5-3.3 vs. healthy: 1.5 days, range 0.7-2.5 (p = 0.10)), right SCTT (CF: 0.5 day, range 0-1.1 vs. healthy: 0.4 day, range 0-1.0 (p = 0.85)), or left SCTT (CF: 1.0 day, range 0-2.2 vs. healthy 0.6 day, range 0.2-1.2 (p = 0.10)).

CONCLUSIONS

In spite of normal contraction patterns, overall passage through the small intestine is significantly delayed in CF patients while upper small intestinal transit may be abnormally fast.

Effects of daily fat or ethanol ingestion on the cholecystokinin- pancreas and the gastrin- enterochromaffin-like cell axes in rats

BACKGROUND/AIMS

Ingestion of fat and ethanol is thought to contribute to the development of pancreatitis through the release of gut hormones, such as cholecystokinin (CCK) and gastrin. We have examined the effects of fat or ethanol on the relationships between CCK and pancreas on one hand and between gastrin and the enterochromaffin-like (ECL) cells in the stomach on the other.

METHODS

In one study, rats received 2 ml of medium-chain triglycerides or water twice a day by the oral route for 12 days. In another study, rats received 2.5, 5, 10 or 20% ethanol in drinking water for 12 days. All rats were killed on day 13.

RESULTS

There were no changes in either the plasma CCK concentration or the pancreatic weight and DNA content in the fat-fed rats. The serum gastrin concentration and the histidine decarboxylase (HDC) activity, HDC mRNA level and histamine content of the ECL cells were lower in fat-fed rats than in control rats. Ethanol did not affect either the plasma CCK concentration or the pancreatic weight and DNA content. The serum gastrin concentration was reduced in the rats that received 5, 10 or 20% ethanol. Also the HDC activity and histamine content of the ECL cells were reduced in the rats that received 10 and 20% ethanol.

CONCLUSION

Daily ingestion of fat or ethanol for 12 days was without effects on the plasma CCK concentration and the pancreas, but reduced the serum gastrin concentration and the activity of the ECL cells in the rat.