Functional expression of single-chain antibody to leukotriene C4

Leukotriene C 4 (LTC 4 ) is synthesized by binding of glutathione to LTA 4 , an epoxide derived from arachidonic acid, and further metabolized to LTD 4 and LTE 4 . We previously prepared a monoclonal antibody with a high affinity and specificity to LTC 4 . To explore the structure of the antigen-binding site of a monoclonal antibody against LTC 4 (mAbLTC), we isolated full-length cDNAs for heavy and light chains of mAbLTC. The heavy and light chains consisted of 461 and 238 amino acids including a signal peptide with molecular weights of 51,089 and 26,340, respectively. An expression plasmid encoding a single-chain antibody comprising variable regions of mAbLTC heavy and light chains (scFvLTC) was constructed and expressed in COS-7 cells. The recombinant scFvLTC showed a high affinity with LTC 4 comparable to mAbLTC. The scFvLTC also bound to LTD 4 and LTE 4 with 48% and 17% reactivities, respectively, as compared with LTC 4 binding, whereas the antibody showed almost no affinity for LTB 4 .