It was first described in 1985 as a bladder tumour antigen (Banchereau et al, 1994) but this was largely overlooked when subsequent investigation revealed its pivotal role in B-cell function, where ligation with CD40 ligand (CD40L or CD154) expressed on activated T-helper cells stimulates cell maturation, proliferation and immunoglobulin class switching. Here, CD40LG is linked to urinary bladder neoplasm.