Significance of Ficolin 2 in the Determination of Serological Activity in Chronic Inflammatory Bowel Disease

Background

Background Like mannan-binding lectin (MBL), ficolins are important soluble receptors for microbial associated molecular patterns leading to the activation of the lectin pathway complement. Ficolins are structurally related to MBL, but due to their different carbohydrate recognition domain represent an own family of lectins (1). The single polypeptide chains of ficolins form trimers and the trimers finally form higher order structures (tetramers up to hexamers) which constitute the functional protein. Humans have three ficolins: Ficolin-1 (M-ficolin), -2 (L-ficolin) and -3 (H-ficolin), whereas ficolin-2 and -3 are present in the serum, ficolin-1 is found on the surface of monocytes. Both, ficolin-2 and -3 are produced in the liver with an additional source for ficolin-3 in the lung. Like MBL, ficolins have to assemble with the MBL-associated serin proteases (MASPs) in order to activate the complement pathway (1). In our study on a possible role for the influence of the complement system in the development of CD-associated anti-Saccharomyces cerevisiae antibodies (ASCAs), we noticed that chronic inflammatory bowel disease (CIBD) patients, specifically Crohn's disease (CD) patients, exhibited high serum ficolin 2 concentrations.

Our research group is interested in the interaction of the innate immune system with microorganisms of the intestinal flora, focusing on possible defects in innate immune mechanisms. We have more than ten years experience in the field, with a special focus on ASCA and MBL. We have been able to continuously publish our work about these theories.

Our earlier and present studies on the role of MBL and the lectin pathway of complement in CD led to the finding of increased ficolin-2 concentration in the sera of CD patients. Moreover, we found that CD patients with a Harvey-Bradshaw index >3 had significantly higher ficolin 2 concentrations than those with a Harvey-Bradshaw index of ≤ 3.

Study Hypotheses

The following hypotheses are to be tested:

1. The ficolin 2 concentration is higher in Crohn's patients with active disease than in CD patients in remission.
2. Ficolin 2 correlates with endoscopic activity.
3. Ficolin 2 correlates with calprotectin.

Objective

The findings from the first part of the study are to be confirmed in a prospective and more detailed study with a larger patient cohort, testing our (new) working hypothesis that ficolin 2 represents a serum marker for disease activity in CD.

Since it is currently difficult to reliably determine disease activity in CD patients using serum and stool markers without simultaneous endoscopic examination, another specific and easy to obtain disease marker which correlates well with disease activity would be highly welcome. Particularly because the current standard marker, to monitor disease activity (faecal calprotectin), is much less accepted than testing for parameters in the blood.

Therefore, the study aims at answering the question of whether ficolin 2 is present in greater concentrations in the blood of Crohn's patients with active inflammation compared to CD patients in remission or to ulcerative colitis (UC) patients.

Methods

For the purposes of the study, the endoscopic activity index will be recorded using the SES-CD (simplified endoscopic score for CD) for Crohn's patients and the Mayo score for colitis patients.

Approximately 5 ml blood will be taken to prepare serum. (5.5 ml or 4.9 ml S Monovette or 4.7 ml or 4.9 ml serum gel Monovette).

A second test tube of blood will be taken for CRP determination. In order to measure calprotectin, the patient will be asked to provide a stool sample shortly before or shortly after the endoscopic examination (within one week).

Serum ficolin values are measured by enzyme-linked immune sorbent assay (ELISA) in the laboratory at the Department of Clinical Research, University of Bern; all other values are determined in routine diagnostic laboratories.