Antibodies to Saccharomyces cerevisiae in patients with Crohn's disease and their possible pathogenic importance.

Saccharomyces cerevisiae (baker's yeast) may play an important part in the pathogenesis of Crohn's disease. Because of this the levels of IgG and IgA antibodies against three S cerevisiae strains (NCYC 77, NCYC 79, and NCYC 1108) were assayed in 49 patients with Crohn's disease, 43 with ulcerative colitis, 14 with coeliac disease, and 21 healthy controls. Coded serum samples were tested by ELISA. Similar antibody patterns to all three strains were found. IgG and IgA antibody levels were significantly raised in patients with Crohn's disease compared with healthy controls (p < 0.001 and p < 0.0001 respectively) and with ulcerative colitis patients (p < 0.0001 and p < 0.0006 respectively). Raised IgA, but not IgG, yeast antibody levels were found in two patients with Crohn's disease who were intolerant to yeast, but these values were similar to those in other patients without yeast intolerance. In ulcerative colitis, both IgG and IgA levels were similar to normal controls. Patients with small bowel Crohn's disease had significantly higher IgG antibody levels than those with colonic disease (p < 0.01). High levels of IgG, but not IgA, antibody were present in patients with coeliac disease, the antibody responses being indistinguishable from those found in Crohn's disease. It is concluded that the presence of IgG antibody to S cerevisiae is characteristic but not specific to Crohn's disease. Although raised IgA antibody levels are more frequently found in Crohn's disease, their pathogenic importance remains to be established.