Changes in mucosal immune cells of bladder tumor patient after BCG intravesical immunotherapy

The Bacillus Calmette-Guerin (BCG) is considered to be at least as effectiv e, and perhaps superior to chemotherapy in the prophylaxis of recurrent sup erficial tumors. However, the mechanism of the antitumor effect of BCG is s till not exactly known. We have conducted investigations to examine changes in bladder mucosal immune cells in patients with superficial bladder carci noma treated with a first cycle of BCG. The study group included 15 BCG and 5 doxorubicin instillation patients, most in the intermediate or high risk group for recurrent tumor. Grossly normal bladder mucosal cold cup biopsie s were performed at initial TUR and one week after six consecutive weekly i nstillations of BCG or doxorubicin. All specimens underwent immunohistochem ical staining, both pre-treatment and post-treatment, including CD20, CD45R O, CD8, CD4 and CD57. Immunoreactive cell counts were evaluated from three different microscopic fields (x400) under the grid. The mean duration of fo llow-up was 52.8 months. The post-treatment bladder mucosal B-cells (CD20) and T-cells (CD45RO, CD4, CD8) were significantly increased compared to pre -treatment in patients treated with BCG instillation, but NK-cells (CD57) w ere not changed. However, there was no change in B-cells or T-cells in pati ent treated with doxorubicin. The CD20 cells in pre-treatment specimens did not correlate with any other cells. However, it was a statistically signif icant correlation with CD45RO in post-treatment specimens. The CD4 correlat ed with CD45RO and CD8 in pre-treatment, but it was correlated with CD45RO and CD57 in post-treatment specimens. There was no tumor recurrence in case s with significantly increased B-cells after BCG instillation. The results of these studies suggest that intravesical BCG immunotherapy for superficia l bladder tumor induces a significant increase in T-cells as well as B-cell s and that B-cells have a preventive effect on tumor recurrence. Further st udies with a larger number of patients are needed to confirm the value of t he B-cell increment after BCG instillation as a clinically independent prog nostic factor.