Activated CD19+ B cell lamina propria lymphocytes in ulcerative colitis.

Although isotype differences in lamina propria lymphocyte (LPL) immunoglobulin production has been recognized between normal, ulcerative colitis (UC) and Crohn's patients, differences in B cell activation between these conditions has not been described. Using flow cytometry, we studied B cell LPL activation using the CD71 (transferrin receptor), CD25 (interleukin-2 receptor) and 4F2 (early B and T cell activation marker) monoclonal antibodies. CD19+ B cells from patients with UC had relatively increased expression of CD71, CD25 and 4F2 compared with patients with Crohn's disease or normal mucosa. This finding corresponds to an increased proportion of transitional (activated) B cells as defined by the co-expression of CD45RA and CD45RO found in UC LPL compared with normal or Crohn's patient LPL. Such data may identify an important link between the cellular state of activation of UC LPL B cells and the differences in immunoglobulin production between the inflammatory bowel diseases and normal intestine. Such findings may have further diagnostic or pathophysiologic importance in the study of these diseases. This work also provides further support for the CD45 transition of CD19 B cells from the high to low molecular weight isoform.