Autoantibodies against exocrine pancreas in Crohn's disease are directed against two antigens: the glycoproteins CUZD1 and GP2

BACKGROUND

Autoantibodies against exocrine pancreas (PAb) have been reported to be pathognomonic markers of Crohn's disease (CD). Recently, the glycoprotein GP2 has been proposed as the exclusive target for PAb but two equally prevalent binding patterns can be observed in the indirect immunofluorescence test (IIFT) using cryosections of human pancreas: a reticulogranular and a droplet pattern.

AIM

To identify autoantigens corresponding to the staining patterns.

METHODS

Different lectins were screened for their ability to immobilize PAb-reactive glycoproteins from cell free human pancreas. The glycoproteins were then purified via UEA-I affinity chromatography and identified by mass spectrometry. The two candidate autoantigens were separately expressed in HEK293 cells, and the recombinant cells applied as substrates in IIFT to analyze sera from 96 patients with CD, 89 controls and hybridoma supernatants during the generation of murine monoclonal antibodies.

RESULTS

The UEA-I eluate was able to neutralize PAb reactivity of both patterns in IIFT. It contained two major constituents which were identified as the glycoproteins CUZD1 and GP2. With the recombinant cells, 35.4% of the CD patients exhibited positive reactions (CUZD1 alone 19.8%, GP2 alone 9.4%, and both antigens 6.2%). The reaction with the CUZD1 expressing cells was strictly correlated to the reticulogranular pattern, whereas the antibodies causing the droplet pattern stained the GP2 expressing cells. Antigen-capture ELISA using the newly generated monoclonal antibodies against CUZD1 and GP2 verified this relationship.

CONCLUSIONS

The concordant reactivities of the different platforms can be regarded as a proof for the authenticity of the two identified autoantigens.

Diabetes impairs mobilization of mouse bone marrow-derived Lin(-)/VEGF-R2(+) progenitor cells

Endothelial progenitor cells circulating in the peripheral blood (PB) contribute to vascular repair. This study aimed to evaluate the potential of a 'cocktail' consisting of erythropoietin, granulocyte colony-stimulating factor and tetrahydrobiopterin to mobilize hematopoietic lineage negative/vascular endothelial growth factor receptor 2 positive (Lin(-)/VEGF-R2(+)) cells from the bone marrow (BM) to PB in non-diabetic and diabetic mice. Diabetes was induced in mice by intraperitoneal injection of streptozotocin. Diabetic mice were studied after 16weeks of hyperglycemia. Half the mice in each group (non-diabetic and diabetic) received daily intraperitoneal injections of the cocktail for 6 consecutive days while the other half received vehicle buffer. Mobilization of Lin(-)/VEGF-R2(+) cells, which were expanded in MCP301 medium, was evaluated after isolating them from BM and PB and their phenotypic and morphological properties were studied. We found that 16weeks of diabetes affected neither the total number of BM mononucleated cells nor the number of Lin(-)/VEGF-R2(+) cells in BM compared with non-diabetic controls. In non-diabetic mice, cocktail treatment resulted in a significant decrease in BM Lin(-)/VEGF-R2(+) cells, paralleled by a significant increase of these cells in PB. Such changes in the number of Lin(-)/VEGF-R2(+) cells in BM and PB after the cocktail treatment were less marked in diabetic mice. In vitro studies of BM Lin(-)/VEGF-R2(+) cells from diabetic and non-diabetic mice did not reveal any differences in either phenotypes or colony forming potential. These findings indicate that diabetes impairs the mobilization of Lin(-)/VEGF-R2(+) cells from BM to PB. Impaired mobilization of BM Lin(-)/VEGF-R2(+) cells soon after the onset of diabetes may contribute to complications such as diabetic retinopathy.