Identification of hybrid-type carbohydrate chains on the light chain of human monoclonal antibody specific to lung adenocarcinoma.

The carbohydrate chains on the light chains of human monoclonal antibody HB4C5 reactive to human lung adenocarcinoma tissue have been characterized. The HB4C5 antibody consists of two kinds of light chains (30 kDa and 32 kDa). Each chain has different carbohydrates of varying molecular masses linked to the variable regions. The 30 kDa light chain has been confirmed to be the active species for antibody binding. The carbohydrates on the light chains were characterized by lectin blot analysis combined with glycosidase treatment. A carbohydrate chain linked to the active 30 kDa light-chain species, and one of a few carbohydrate phenotypes on the 32 kDa light-chain species is characterized as "hybrid type". A sialylated complex-type carbohydrate could also bind to the 32 kDa light-chain species. Nucleotide sequence analysis revealed that one potential N-glycosylation site is located in the complementarity determining region 1 of the light chain, although no such site was found in the variable region of the heavy chain.