Expression of a novel autoantibody defined by the VH3-15 gene in inflammatory bowel disease and Campylobacter jejuni enterocolitis.

This study newly introduces anti-VH mAbs to assess the role of clonal B cell activity in inflammatory bowel disease. Immunohistochemistry of colonic biopsies in ulcerative colitis (UC) and Crohn's disease (CD), but not unaffected individuals, demonstrated uniform staining of intravascular erythrocytes with BK2, a monoclonal specific for the VH3-15 Ig heavy chain gene product. Staining was caused by erythrocytes opsinized in vivo by anti-erythrocyte Abs present in patient sera and by using the VH3-15 gene product. The erythrocyte Ag was identified by immunoprecipitation as 22- and 28-kDa membrane proteins. A direct flow cytometric assay was developed to measure this serum autoantibody and was tested in 101 individuals with UC, CD, other acute or chronic colitis, and healthy controls. Compared with normal subjects, BK2+ anti-erythrocyte Abs were elevated in most sera from patients with CD and UC (including postcolectomy). BK2+ anti-erythrocyte Abs also were elevated in 10 of 38 noninflammatory bowel disease patients, all of whom had Campylobacter jejuni enterocolitis. These findings suggest that a common immunopathogenetic factor, manifested by VH3-15 B cell activation may be shared in UC, CD, and Campylobacter jejuni enterocolitis.