B1a lymphocytes in the rectal mucosa of ulcerative colitis patients

To assess B1a cell expression in the rectal mucosa of ulcerative colitis (UC) patients in comparison with healthy controls.

Rectal mucosa biopsies were collected from 15 UC patients and 17 healthy controls. CD5(+) B cells were analysed by three colour flow cytometry from rectal mucosal samples after mechanical disaggregation by Medimachine(®). Immunohistochemical analysis of B and T lymphocytes was also performed. Correlations between, on the one hand, rectal B1a cell concentrations and, on the other, erythrocyte sedimentation rate and C-reactive protein levels and clinical, endoscopic and histological disease activity indices were evaluated.

Rectal B-lymphocyte (CD19(+)/CD45(+)) rate and concentration were higher in UC patients compared with those in healthy controls (47.85% ± 3.12% vs 26.10% ± 3.40%, P = 0.001 and 501 ± 91 cells/mm(2) vs 117 ± 18 cells/mm(2), P < 0.001); Rectal B1a cell density (CD5(+)CD19(+)) was higher in UC patients than in healthy controls (85 ± 15 cells/mm(2) vs 31 ± 6.7 cells/mm(2), P = 0.009). Rectal B1a cell (CD5/CD19(+)) rate correlated inversely with endoscopic classification (Rs = -0.637, P < 0.05).

B1a lymphocytes seem to be involved in the pathogenesis of UC, however, the role they play in its early phases and in disease activity, have yet to be defined.