Intravesical BCG administration in the guinea pig. II. Immunohistochemical characterization of cellular infiltrate after one or two cycles of intravesical BCG.

The intravesical administration of bacillus Calmette-Guérin (BCG) is used as an adjuvant therapy after transurethral resection for superficial bladder cancer in man. The aim of this study was to characterize with monoclonal antibodies the cellular infiltrates in the bladder wall occurring after one or two cycles, each comprising six weekly intravesical BCG administrations in guinea pigs. BCG-RIVM and BCG-TICE were instilled once a week in undamaged bladders at weeks 1-6 and 11-16, respectively, and retained in the bladder for 1 h. Autopsy was performed 1 week after the last BCG administration at weeks 7 and 17. By routine histology, a single BCG course induced scattered focal infiltrates consisting of minor to severe accumulations of mononuclear cells. After two cycles of BCG, a much more severe inflammatory reaction sometimes occupying almost the total bladder mucosa was noted. The major component of this inflammation was mononuclear cells, mainly lymphocytes, while typical BCG granulomas were occasionally observed. In general, the epithelial layer of the bladder showed no visible alterations. Immunohistochemical staining showed that the majority of mononuclear cells present in the infiltrate were T-cells. Widely scattered B-cells and macrophages were also present, but were much fewer in number than the T-cells. In general, T-helper/inducer cells were more frequent than T-suppressor/cytotoxic cells. Pseudofollicles, also noted after H&E staining, consisted mainly of B-cells. The second series of BCG administrations produced pseudofollicles in the infiltrates in all animals investigated.(ABSTRACT TRUNCATED AT 250 WORDS)