Anti–Saccharomyces cerevisiae antibody

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  S. cerevisiae under DIC microscopy
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  C. albicans

Anti–Saccharomyces cerevisiae antibody

Anti–Saccharomyces cerevisiae antibodies (ASCA) are a type of antibody directed against Saccharomyces cerevisiae, a species of yeast commonly used in baking and brewing. These antibodies are of clinical interest because they are often found in patients with certain inflammatory bowel diseases (IBD), particularly Crohn's disease.

Structure and Function

ASCA are typically of the IgA and IgG classes of antibodies. They are produced by the immune system in response to antigens from Saccharomyces cerevisiae. The exact role of ASCA in the pathogenesis of Crohn's disease is not fully understood, but their presence is thought to reflect an abnormal immune response to intestinal microbiota.

Clinical Significance

ASCA are used as a serological marker in the diagnosis and differentiation of IBD. They are more commonly associated with Crohn's disease than with ulcerative colitis. The presence of ASCA can help distinguish Crohn's disease from ulcerative colitis, as ASCA are found in approximately 60-70% of patients with Crohn's disease but are less common in those with ulcerative colitis.

Diagnostic Use

The detection of ASCA is performed using enzyme-linked immunosorbent assay (ELISA) or immunofluorescence. The presence of ASCA, along with other serological markers such as perinuclear anti-neutrophil cytoplasmic antibodies (pANCA), can aid in the diagnosis and classification of IBD. A positive ASCA test, especially when combined with a negative pANCA test, is suggestive of Crohn's disease.

Pathophysiology

The pathophysiology of ASCA in Crohn's disease involves an abnormal immune response to the yeast Saccharomyces cerevisiae. It is hypothesized that in genetically susceptible individuals, exposure to certain antigens from the yeast may trigger an immune response that contributes to the chronic inflammation seen in Crohn's disease. However, the exact mechanisms remain an area of active research.

Limitations

While ASCA are useful in the context of IBD diagnosis, they are not definitive. Not all patients with Crohn's disease will have ASCA, and some healthy individuals may test positive for ASCA without having any symptoms of IBD. Therefore, ASCA testing should be used in conjunction with other diagnostic methods, including clinical evaluation and endoscopy.

Related pages

• Crohn's disease
• Ulcerative colitis
• Inflammatory bowel disease
• Antibody
• Enzyme-linked immunosorbent assay