Single cell suspensions were prepared from MB49 and MB49-I tumours growing in vivo in bladders, and analysed by multicolour flow cytometry after surface staining for the presence of CD19+ B cells, NK cells, CD4+ T cells, CD8+ T cells, CD4+/Foxp3+ regulatory T cells (Treg) (Fig 2A), and after intracellular staining for production of cytokines by T cells (Fig 2B). The gene discussed is CD19; the disease is neoplasm.