Circulating granulocyte antibodies in first attacks of colitis

Multidimensional degradomics identifies systemic autoantigens and intracellular matrix proteins as novel gelatinase B/MMP-9 substrates

The action radius of matrix metalloproteinases or MMPs is not restricted to massive extracellular matrix (ECM) degradation, it extends to the proteolysis of numerous secreted and membrane-bound proteins. Although many instances exist in which cells disintegrate, often in conjunction with induction of MMPs, the intracellular MMP substrate repertoire or degradome remains relatively unexplored. We started an unbiased exploration of the proteolytic modification of intracellular proteins by MMPs, using gelatinase B/MMP-9 as a model enzyme. To this end, multidimensional degradomics technology was developed by the integration of broadly available biotechniques. In this way, 100-200 MMP-9 candidate substrates were isolated, of which 69 were identified. Integration of these results with the known biological functions of the substrates revealed many novel MMP-9 substrates from the intracellular matrix (ICM), such as actin, tubulin, gelsolin, moesin, ezrin, Arp2/3 complex subunits, filamin B and stathmin. About 2/3 of the identified candidates were autoantigens described in multiple autoimmune conditions and in cancer (e.g. annexin I, nucleolin, citrate synthase, HMGB1, alpha-enolase, histidyl-tRNA synthetase, HSP27, HSC70, HSP90, snRNP D3). These findings led to the insight that MMPs and other proteases may have novel (immuno)regulatory properties by the clearance of toxic and immunogenic burdens of abundant ICM proteins released after extensive necrosis. In line with the extracellular processing of organ-specific autoantigens, proteolysis might also assist in the generation of immunodominant 'neo-epitopes' from systemic autoantigens. The study of proteolysis of ICM molecules, autoantigens, alarmins and other crucial intracellular molecules may result in the discovery of novel roles for proteolytic modification.

Are anti-neutrophil cytoplasmic antibodies (ANCA) clinically useful in inflammatory bowel disease (IBD)?

Since the first detection of ANCA in IBD, numerous studies have dealt with their prevalence, antigenic specificities, clinical significance, pathophysiological role, and their induction. This review summarizes the information obtained from those studies and shows that ANCA are not directly useful as diagnostic and prognostic factors in IBD. ANCA were detected in 50-85% of patients with ulcerative colitis (UC) and 10-20% of patients with Crohn's disease (CD). Multiple target antigens are recognized by these autoantibodies, including both cytoplasmic and nuclear proteins. A pathophysiological role for ANCA in IBD is far from clear. On the one hand, it is suggested that ANCA are genetic markers of susceptibility for IBD, and on the other hand, the induction of ANCA in those diseases may just be an epiphenomenon of chronic inflammation. We discuss recent evidence that ANCA may be induced by a break-through of tolerance towards bacterial antigens.

Antineutrophil cytoplasmic antibodies in Japanese patients with inflammatory bowel disease: prevalence and recognition of putative antigens

OBJECTIVE

Our aim was to investigate the prevalence of antineutrophil cytoplasmic antibodies (ANCA) in Japanese patients with ulcerative colitis (UC) and Crohn's disease (CD), and the putative antigens recognized by perinuclear staining pattern ANCA (p-ANCA)-positive sera.

METHODS

Sera from UC (n = 52) and CD (n = 43) patients, and from healthy controls (n = 74) were studied. The indirect immunofluorescence (IIF) method was used for the detection of ANCA and its binding pattern. p-ANCA-positive sera were studied further for putative antigens. ELISAs using lactoferrin (Lf), myeloperoxidase (MPO), and cathepsin G (Cat G) as antigens were performed.

RESULTS

ANCA was positive in 40 of the 52 (76.9%) UC (p-ANCA in 33) and in 32 of the 43 (74.4%) CD (p-ANCA in 31) patients. UC and CD patients showed significantly higher titers of p-ANCA than controls; however, no significant difference was observed between UC and CD. In UC, 23, 17, and nine of the 33 patients with p-ANCA-positive sera showed reactivity with Lf, MPO, and Cat-G, respectively. In CD, 21, 20, and 11 of the 31 patients with p-ANCA-positive sera showed reactivity with Lf, MPO, and Cat-G, respectively. Fourteen of the UC and six of the CD patients showed reactivity with two different antigens, and seven of the UC and 11 of the CD patients showed reactivity with all three antigens. The presence of anti-Lf and anti-MPO antibodies was further confirmed by Western blotting.

CONCLUSIONS

ANCA is useful in distinguishing patients with IBD from normal subjects but is not sufficient for the differential diagnosis of CD and UC. p-ANCA reactivity might be derived from the recognition of heterogeneous neutrophil-associated antigens.

The presence of anti-neutrophil antibodies reflects clinical and genetic heterogeneity within inflammatory bowel disease

A detailed investigation of the relationship between anti-neutrophil cytoplasmic antibodies (ANCA) status, HLA genotype, and clinical patterns of inflammatory bowel disease was carried out, involving 236 European patients resident in the United Kingdom [120 had ulcerative colitis (UC), 116 had Crohn's disease (CD)]. ANCA status was determined on coded plasma samples in Los Angeles using a two-stage assay [fixed neutrophil enzyme-linked immunosorbent assay (ELISA) and indirect immunofluorescence], and HLA genotyping was carried out by polymerase chain reaction. The results provide evidence that ANCA reflect clinical and genetic heterogeneity within the inflammatory bowel diseases. In the UC patients, 78.3% were ANCA positive [64.2 perinuclear (pANCA)], but only 46.5% CD patients were ANCA positive (19.3% pANCA). Furthermore, mean ELISA binding was significantly lower in CD (14.5% +/- 18.8% versus 40.5% +/- 41.0% in UC, p = 2.31 x 10(-9)). Only 15 CD samples, all from patients with colonic disease, displayed ELISA > 20%; and the six CD patients with highest ELISA binding had clinical features very similar to ulcerative colitis. Moreover, in UC, significant relationships between ANCA status and genotype were noted. Thus, 92.7% of patients with the DR3 DQ2 TNF2 haplotype were ANCA positive [p = 0.03 versus DR3 DQ2 TNF2-negative patients (73.9%)]. ELISA binding was increased in DR3 DQ2 TNF2-positive patients (56.0 versus 35.7%, p = 0.02). In this population of UC, ANCA was not associated with DR2, DR4, or clinical pattern. These data emphasize the many factors that need to be considered in genetic marker studies in inflammatory bowel disease. Extensive disease heterogeneity, ethnicity, and methodological differences in ANCA detection are all pertinent.