Tracking of B cells with Cμ deletion in various tissues by PCR. The frequency (%) of positive samples is represented by horizontal columns and the numbers (n) of analyzed individual samples are indicated on the left. Detection of a single or multiple clones was graded according to the number of PCR products revealed (≥ 2 electrophoretic bands, indicated by ▧; see Figure 1B). Of the 4 positive samples (9%) of small bowel mucosa, 3 were histologically normal and 1 had celiac disease. Of the 5 positive samples (28%) of large bowel mucosa, 3 were histologically normal, 1 had Crohn colitis, and 1 had ulcerative colitis.