Anti-mannotriose (Man3) antibodies were previously isolated from a Keio phage library displaying human single chain variable fragments (scFvs) using a neoglycolipid, Man3-dipalmitoylphosphatidylethanolamine. Of three genes constructed, the 5A3 clone was expressed in mouse myeloma NS0 cells as a conjugate with human IgG 1 Fc (scFv-Fc) and characterized (Sakai, K., Shimizu, Y., Chiba, T., MatsumotoTakasaki, A., Kusada, Y., Zhang, W., Nakata, M., Kojima, N., Toma, K., Takayanagi, Since the human genome project was completed, our understanding of structure-function relationships among proteins has made significant advances. In contrast, elucidating the role of carbohydrate modification on the functions of glycoproteins, glycolipids, and peptide glycans remains elusive. The project that was to produce a variety of carbohydrate-specific antibodies by the phage display technology was thus launched in 2003 with the hope that the resulting antibodies could not only provide tools for carbohydrate research but also be applied to diagnostic or therapeutic uses. In vitro production of anti-carbohydrate antibodies is seemingly a logical strategy because carbohydrate moieties are self-antigens by nature. Thus far, researchers have most often preferred to use phage display technologies because they have been successful to a certain extent, in producing antibodies against varieties of carbohydrate moieties of glycoconjugates (1-6). The phage display strategy readily provides genes encoding recombinant antibodies against antigens of interest, which then need to be introduced into prokaryotic or eukaryotic cells for translation of the obtained antibody genes to produce proteins. Unless other in vitro translation systems are employed, this technology cannot provide an absolute in vitro system for production of anti-carbohydrate antibodies.Previously, we reported on producing and characterizing anti-mannotriose (Man3) 4 antibodies (7,8). The objectives of our first study (7) were to establish a new methodology so that single chain variable fragments (scFvs) against desired carbohydrate moieties could be readily isolated, and the objectives of our second paper (8) were to produce soluble scFv proteins in quantity so that purification and characterization of isolated scFvs could be readily accomplished.