Ethnic and socio-cultural specificities in Tunisia have no impact on the prevalence of anti-Saccharomyces cerevisiae antibodies in Crohn's disease patients, their relatives or associated clinical factors.

BACKGROUND: In Western Europe and the USA, the presence of anti-Saccharomyces cerevisiae antibodies (ASCAs) in Crohn's disease (CD) patients and their healthy relatives suggests that ASCAs may be influenced by genetic and/or environmental factors.
OBJECTIVES: To assess the prevalence of ASCAs in Tunisian patients with CD or ulcerative colitis (UC), and unaffected family members, in relation to clinical phenotype. Patients and methods. Seventy-seven patients (39 CD, 38 UC), 66 healthy relatives of CD patients, 16 relatives of UC patients and 70 healthy controls were studied. ASCAs were quantified with a new isotype-specific ELISA test involving an antigenic extract from S. cerevisiae strain W303 and by the original test which detects total immunoglobulins against S. cerevisiae Su1 mannan.
RESULTS: The specificity of the two tests was identical (91%). The isotype-specific ASCA W303 test was more sensitive than the ASCA Su1 test for immunoglobulin detection, but some CD patients were positive only with this latter test. A high percentage of patients with CD (72%) and their unaffected family members (35%) were ASCA-positive in contrast to UC patients (16%) and their relatives (0%) and controls (8.6%). ASCAs were shown to be independent of rural or urban living, disease activity, but were associated with ileal location. The antigen of S. cerevisiae strain W303 discriminated patients depending on age at onset or location of the disease.
CONCLUSION: This study confirms the antigenic heterogeneity of S. cerevisiae strains in their ability to detect ASCA. It suggests that ASCAs are markers of immunoregulatory disturbance in CD, independently of ethnic/cultural differences between Europe, the USA and North Africa.