Keyhole limpet hemocyanin (KLH) (KLH)

Keyhole limpet hemocyanin (KLH) is a large, multi-subunit, copper-containing metalloprotein derived from the hemolymph of the giant keyhole limpet, Megathura crenulata (Harris & Markl, 1999). It is widely recognized for its exceptional immunogenicity in humans, which stems from its high molecular weight and the presence of foreign carbohydrate and peptide epitopes (Swaminathan et al., 2014). In a clinical context, KLH is not a traditional therapeutic target but rather serves as a potent immunostimulant and carrier protein for haptens and poorly immunogenic antigens. When administered, KLH is internalized by dendritic cells, processed into peptides, and presented on MHC class II molecules to T-cell receptors (TCRs), thereby initiating a comprehensive immune response (Lamm et al., 1982). This property is exploited in the treatment of superficial bladder cancer and in the development of therapeutic vaccines for various cancers and infectious diseases (Gebbia et al., 2008). Its role is primarily to enhance the visibility of associated antigens to the immune system, facilitating the production of high-affinity antibodies and the activation of cellular immunity.

Other names

KLHMegathura crenulata hemocyaninKeyhole limpet haemocyanin

KLH acts as a potent T-cell dependent antigen that is processed by dendritic cells and presented on MHC class II molecules to T-cell receptors, thereby stimulating a robust immune response including the production of cytokines and the activation of both B-cells and cytotoxic T-cells.