Numerous oligosaccharides are attached to the surface of the KLH molecule and account for about 4% of its molecular mass. With their intricate topology, these oligosaccharides contribute to KLH’s strong immunogenicity. Although not completely elucidated, different mechanisms of action are at play: non-specific stimulation of the immune system, stimulation of cytotoxic T cells and induction of anti-tumoral antibodies. KLH antibodies can bind to the Thomsen-Friedenreich antigens associated with cancer progression and metastasis on bladder carcinoma cells. The reaction of KLH antibody with Thomsen-Friedenreich antigen leads to phagocytosis and dissolution of the tumor cell. Immunocyanin, the main ingredient in IMMUCOTHEL® for the recurrence prevention of superficial urinary bladder carcinoma, is derived from KLH.