An easy method to quantify plasma cells/plasma cell precursors in normal colonic mucosa, collagenous colitis and Crohn's colitis.

BACKGROUND

The number of round cells that should normally be present in the colonic mucosa remains disputed. Biopsies from patients with chronic diarrhoea, having a slightly increased number of round cells in the lamina propria mucosa (lpm) may be diagnosed as slight chronic colitis by some pathologists, while others may regard these biopsies as being normal.

MATERIALS AND METHODS

The numbers of plasma cells/plasma cell precursors (PC-PCP) were assessed in colonic biopsies from 35 patients by the aid of MUM1 immunostaining. MUM1 (multiple myeloma oncogene 1) is a member of the interferon regulatory family of transcription factors (interferon regulatory factor 4 gene, IRF4).

RESULTS

Many of the round cells considered, as lymphocytes in H&E staining were in fact MUM1-positive PCP. In 6 patients having a priori, a slightly increased number of round cells, the mean number of MUM1-labelled cells was 40.8, in 5 patients with collagenous colitis, it was 81.4 and in 12 patients with Crohn's colitis, 87.6, whereas in 12 normal individuals it was 23.3 (MUM1-positive cells in collagenous-Crohn's colitis vs. normal mucosa, p<0.05).

CONCLUSION

MUM1 was of value in recording a significant increase of PC-PCP in collagenous colitis and Crohn's colitis. The subjective impression of increased cellularity in some colonic biopsies from patients with chronic diarrhoea was substantiated in mathematical terms, by demonstrating that the number of PC-PCP was increased.