Anti-Saccharomyces cerevisiae antibodies (ASCA) are human antibodies that can be detected using an enzyme-linked immunosorbent assay involving a mannose polymer (mannan) extracted from the cell wall of the yeast S. cerevisiae. The ASCA test was developed in 1993 with the aim of differentiating the serological response in two forms of inflammatory bowel disease (IBD), Crohn's disease and ulcerative colitis. The test, which is based on the detection of anti-oligomannosidic antibodies, has been extensively performed worldwide and there have been hundreds of publications on ASCA. The earlier studies concerned the initial diagnostic indications of ASCA and investigations then extended to many human diseases, generally in association with studies on intestinal microorganisms and the interaction of the micro-mycobiome with the immune system. The more information accumulates, the more the mystery of the meaning of ASCA deepens. Many fundamental questions remain unanswered. These questions concern the heterogeneity of ASCA, the mechanisms of their generation and persistence, the existence of self-antigens, and the relationship between ASCA and inflammation and autoimmunity. This review aims to discuss the gray areas concerning the origin of ASCA from an analysis of the literature. Structured around glycobiology and the mannosylated antigens of S. cerevisiae and Candida albicans, this review will address these questions and will try to clarify some lines of thought. The importance of the questions relating to the pathophysiological significance of ASCA goes far beyond IBD, even though these diseases remain the preferred models for their understanding.

This study was designed to assess anti-Saccharomyces cerevisiae antibody positive rate in Behçet's disease and intestinal Behçet's disease and to evaluate whether anti-Saccharomyces cerevisiae antibody expression is associated with clinical findings at diagnosis and clinical course of intestinal Behçet's disease.

One hundred six patients with intestinal Behçet's disease, 30 patients with Behçet's disease, and 45 healthy control subjects were included. Anti-Saccharomyces cerevisiae antibody was detected by indirect immunofluorescence assay. According to anti-Saccharomyces cerevisiae antibody expression, the various parameters at diagnosis, cumulative relapse rates, and cumulative probabilities of operation were analyzed.

Anti-Saccharomyces cerevisiae antibody positive rate was 44.3 percent in intestinal Behçet's disease, 3.3 percent in Behçet's disease, and 8.8 percent in healthy control subjects. In patients with intestinal Behçet's disease, age, gender, distribution of Behçet's disease subtype, symptoms, laboratory tests, and colonoscopic findings at diagnosis were not different according to anti-Saccharomyces cerevisiae antibody expression. Cumulative probability of a first operation was significantly higher in anti-Saccharomyces cerevisiae antibody (+) intestinal Behçet's disease than in anti-Saccharomyces cerevisiae antibody (-) intestinal Behçet's disease: 44.8 and 17.2 percent at one year, and 53 and 24.3 percent at two years after diagnosis, respectively (P=0.006). The number of patients who underwent two or more operations was higher in anti-Saccharomyces cerevisiae antibody (+) intestinal Behçet's disease than in anti-Saccharomyces cerevisiae antibody (-) intestinal Behçet's disease (21.3 vs. 8.5 percent). The cumulative relapse rates were not different between the two groups.

Anti-Saccharomyces cerevisiae antibody positive rate was 44.3 percent in intestinal Behçet's disease. Clinical findings at diagnosis and cumulative relapse rates of intestinal Behçet's disease were not found to be associated with anti-Saccharomyces cerevisiae antibody expression. However, patients with anti-Saccharomyces cerevisiae antibody (+) intestinal Behçet's disease were more likely to receive surgical treatment.

Antibodies directed against oligomannose sequences alpha-1,3 Man (alpha-1,2 Man alpha-1,2 Man)(n) (n = 1 or 2), termed anti-Saccharomyces cerevisiae antibodies (ASCAs) are markers of Crohn's disease (CD). S. cerevisiae mannan, which expresses these haptens, is used to detect ASCA, but the exact immunogen for ASCA is unknown. Structural and genetic studies have shown that Candida albicans produces mannosyltransferase enzymes that can synthesize S cerevisiae oligomannose sequences depending on growth conditions. This study investigated whether C. albicans could act as an immunogen for ASCA.

Sequential sera were collected from patients with CD, systemic candidiasis, and rabbits infected with C. albicans. Antibodies were purified by using chemically synthesized (Sigma) ASCA major epitopes. These affinity-purified antibodies and lectins were then used to analyze the expression of ASCA epitopes on molecular extracts and cell walls of C. albicans and S cerevisiae grown in various conditions.

In humans and rabbits, generation of ASCA was shown to be associated with the generation of anti-C. albicans antibodies resulting specifically from infection. By using affinity-purified antibodies, C. albicans was shown to express ASCA epitopes on mannoproteins similar to those of S. cerevisiae. By changing the growth conditions, C. albicans mannan was also able to mimic S. cerevisiae mannan in its ability to detect ASCA associated with CD. This overexpression of ASCA epitopes was achieved when C. albicans grew in human tissues.

C. albicans is one of several immunogens for ASCA and may be at the origin of an aberrant immune response in CD.

To explore whether there was anti-Saccharomyces cerevisiae antibodies (ASCA) positivity in our patients with biopsy-confirmed celiac disease.

A cohort of patients with inflammatory bowel diseases (42 patients with Crohn's disease and 10 patients with ulcerative colitis) and gluten sensitive enteropathy (16 patients) from Debrecen, Hungary were enrolled in the study. The diagnosis was made using the formally accepted criteria. Perinuclear antineutrophil cytoplasmic antibodies (pANCA) and anti-Saccharomyces cerevisiae antibodies (ASCA), antiendomysium antibodies (EMA), antigliadin antibodies (AGA) and anti human tissue transglutaminase antibodies (tTGA) were investigated.

The results showed that ASCA positivity occurred not only in Crohn's disease but also in Celiac disease and in these cases both the IgG and IgA type antibodies were proved.

It is conceivable that ASCA positivity correlates with the (auto-) immune inflammation of small intestines and it is a specific marker of Crohn's disease.

Elevation of the serum anti-Saccharomyces cerevisiae antibody (ASCA) level has been reported in patients with Crohn's disease. This study investigated the antigenic distribution of S. cerevisiae in human colon and peripheral leukocytes. ASCA was isolated from sera from patients with Crohn's disease using immuno-affinity chromatography and then biotinylated and assayed immunohistologically and immunocytologically to determine the distribution of antigens recognized by ASCA in human colon and peripheral leukocytes. Immunoblot analysis of yeast extract and human peripheral leukocytes was performed. Immunohistological study using biotinylated ASCA revealed the presence of yeast-like particles in the granulation tissue of inflamed colonic mucosa. Biotinylated ASCA also stained lymphocytes and polymorphonuclear cells infiltrating inflamed intestine. Monocytes in epithelioid granulomas of colon with Crohn's disease were also stained. Polymorphonuclear leukocytes in peripheral blood were also stained with biotinylated ASCA. The antigens reactive to ASCA among heat-extracted, non-heat-extracted yeast antigens, and human leukocyte extract differed. The findings of cross-reactivity of polymorphonuclear leukocytes with S. cerevisiae antigen and the presence of S. cerevisiae antigen in Crohn's disease granulomas suggest the possibility of involvement of S. cerevisiae in the pathogenesis of Crohn's disease.

Food antigens may contribute to gut inflammation in Crohn's disease.

To assess in vivo sensitization to food antigens, ascertain whether sensitivity is gut specific, assess food sensitization in vitro, and correlate in vivo changes with histological and blood changes.

Skin testing and rectal exposure to six food antigens (cereal, cabbage, citrus, milk, yeast and peanut) and control saline were assessed double-blind by immediate and 3.5-h laser Doppler blood flowmetry, and rectal biopsies were taken. Peripheral blood lymphocyte proliferation was measured in response to the same antigens.

Ten patients with Crohn's disease and 10 healthy controls were studied. Blood flow increased in 24 of 60 antigen sites in Crohn's disease patients and six of 60 antigen sites in controls (P < 0.0001) after 3.5 h. The Crohn's disease group demonstrated higher rectal blood flow than controls in response to all food antigens, and this was significantly different for the responses to yeast (P = 0.036) and citrus fruits (P = 0.038). Lymphocyte proliferation occurred in 32 of 60 tests in Crohn's disease patients and eight of 60 tests in controls (P < 0.0001). There were no skin responses. Submucosal oedema corresponded to increased mucosal flow.

Crohn's disease patients demonstrate in vivo and in vitro sensitization to food antigens, which is gut specific. Mucosal flowmetry allows the identification of sensitization to gut antigens.

Serology is reported to be helpful in evaluating children for inflammatory bowel disease (IBD), and distinguishing chronic ulcerative colitis (CUC) from Crohn's disease (CD). The markers include perinuclear staining antineutrophil cytoplasmic antibody (pANCA) for CUC and anti-Saccharomyces cerevisiae antibody (ASCA) for CD. In the clinical setting, hemoglobin (Hgb) and erythrocyte sedimentation rate (ESR) are commonly performed for screening symptomatic children for IBD. We examined whether there was an additional benefit of serology in addition to specific symptoms and routine laboratory tests in screening for IBD.

Medical record data was reviewed on children investigated for IBD from February 1999 to April 2001. Children were included if they had blood analyzed for pANCA and ASCA, Hgb, ESR, and colonoscopy as part of their assessment.

Of 177 cases reviewed, 51 were diagnosed with CUC, 39 with CD, and 26 other inflammatory conditions. Visible rectal bleeding was the most discriminating symptom (occurred in 60/90 cases of IBD and 5/61 without IBD). There was a significant difference between the proportion with CUC positive for pANCA (42/51) and those with abnormal Hgb and ESR (30/51) (p < 0.05), but not between children with CD who were ASCA positive (18/39) and those with abnormal Hgb and ESR (26/39) (p = 0.27). The sensitivity and specificity of combined pANCA and ASCA was 68% and 92%, respectively. For the combination of Hgb, ESR, and the presence of rectal bleeding the respective values were 86% and 67%. Serology combined with Hgb and ESR and rectal bleeding as independent factors significantly (p < 0.05) improved sensitivity (89%) but reduced specificity (60%). Screening with the combination of rectal bleeding, Hgb, and ESR identified 86% (77/90) patients with IBD prior to an endoscopic procedure. A further 3 of 90 (3.3%) screened positive with the addition of serology.

Serology tests have a high degree of specificity for IBD while routine laboratory test have a higher sensitivity. When serology is combined with rectal bleeding, Hgb, and ESR, the sensitivity of screening children for IBD is significantly improved. However the large majority of children with IBD can be identified with a clinical history and routine laboratory tests as needing an endoscopic procedure with little benefit of adding serology.

The heat-stable and soluble glycoprotein gp200 (molecular weight 200 kDa) is part of the cell wall of S. cerevisiae. Recently, an association was shown between IgA and IgG against gp200 and inflammation in Crohn's disease. Gp200 is able to induce a proliferation of human lymphocytes in vitro, together with a natural killer cell associated cytotoxicity. Specific IgE against Saccharomyces cerevisiae (baker's or brewer's yeast) may be detected in approximately 73%, against Candida albicans in 68% of those patients suffering from severe atopic dermatitis. The aim of this study was to elucidate the possible role of an anti-gp200 immune response for the pathogenesis of atopic dermatitis by immunoblot analysis. Anti-gp200 IgE was found in 55% of healthy individuals, in 67% of individuals with atopic predisposition without eczema, in 63% of the patients with mild atopic dermatitis, and in 86% of patients with severe atopic dermatitis, respectively. On the contrary, anti-gp200 IgG could be shown in 55% of healthy individuals, in 89% of individuals with atopic predisposition but without eczema, in 100% of patients with mild atopic dermatitis, and in 79% with severe atopic dermatitis, respectively. No immunoreactivity was found when an extract of Arxula adeninivorans was used as antigen. These results underline the specificity of the immunoblot results with gp200 from Saccharomyces cerevisiae. It can be concluded that occurrence of specific IgE against Saccharomyces cerevisiae cannot be explained by a cross reactivity, e.g., against Candida albicans allergens. Further investigations with the recombinant gp200 will give information on the role of this glycoprotein both in atopic dermatitis and Morbus Crohn.

Antibodies to Saccharomyces cerevisiae (ASCA) have been described as specific markers for Crohn disease (CD). The reason for this disease specific generation of antibodies is not clear. Therefore, a family study was performed to evaluate whether the antibody production was due to genetic or environmental factors.

Seventy-one patients with CD, 25 patients with ulcerative colitis (UC), their 282 first-degree relatives, and 32 spouses were included. As controls, 43 sera from healthy persons and 69 sera from patients with various autoimmune disorders were tested for ASCA by indirect immunofluorescence and ELISA.

ASCA were detected in 68% of the patients with CD and in none of the controls, UC patients included. Forty-eight (25%) first-degree relatives of patients with CD were ASCA-positive. ASCA status of relatives was not related to the fact whether these persons lived in the same household with the patients or not. However, one of the spouses of CD patients (4%) was found to be ASCA-positive and the antibody was also found in 5 (6%) of the relatives of UC patients.

ASCA are specific markers for CD. Since these antibodies are found in 25% of first-degree relatives, the generation of ASCA may be mainly related to genetic influences although environmental factors may also play a certain role.