CD45RO EXPRESSION ON CIRCULATING CD19(-CELLS IN CROHNS-DISEASE CORRELATES WITH INTESTINAL PERMEABILITY() B)

Background/Aims: Increased intestinal permeability is observed in Croh n's disease and a subset of first-degree relatives. An alteration in i soform expression of the common leukocyte antigen (CD45) is also found in a significant fraction of patients. Because this alteration may be a measure of antigen exposure, the hypothesis of the study was that t his alteration would be observed in both patients and relatives of pat ients with Crohn's disease and that this would correlate with increase d intestinal permeability. Methods: Lactulose and mannitol permeabilit y were defined in healthy controls, patients with Crohn's disease, and their first-degree relatives. Simultaneously, peripheral blood was as sayed using flow cytometry for CD45RO expression on CD19(+) B cells. R esults: A subset of relatives had significantly increased permeability , as did the majority of patients with Crohn's disease. A small fracti on of peripheral B cells from controls expressed the CD45 isoform (<6% ). This fraction was significantly increased for patients with Crohn's disease and their relatives. Relatives with no clinical evidence of C rohn's disease were only found to have increased CD45RO expression if they had increased permeability. Conclusions: Individuals at risk for developing Crohn's disease include a subset with increased intestinal permeability. These people have an associated phenotypic alteration of circulating B cells that is not observed in controls or relatives wit h normal intestinal permeability.