Lec13 cells, a variant Chinese hamster ovary cell line, were used to produce human IgG1 that were deficient in fucose attached to the Asn 297 -linked carbohydrate but were otherwise similar to that found in IgG1 produced in normal Chinese hamster ovary cell lines and from human serum. Lack of fucose on the IgG1 had no effect on binding to human Fc␥RI, C1q, or the neonatal Fc receptor. Although no change in affinity was found for the His 131 polymorphic form of human Fc␥RIIA, a slight improvement in binding was evident for Fc␥RIIB and the Arg 131 Fc␥RIIA polymorphic form. In contrast, binding of the fucose-deficient IgG1 to human Fc␥RIIIA was improved up to 50-fold. Antibody-dependent cellular cytotoxicity assays using purified peripheral blood monocytes or natural killer cells from several donors showed enhanced cytotoxicity, especially evident at lower antibody concentrations. When combined with an IgG1 Fc protein variant that exhibited enhanced antibody-dependent cellular cytotoxicity, the lack of fucose was synergistic.

The neurotrophins influence survival and maintenance of vertebrate neurons in the embryonic, early post‐natal and post‐developmental stages of the nervous system. Binding of neurotrophins to receptors encoded by the gene family trk initiates signal transduction into the cell. trkA interacts preferably with nerve growth factor (NGF), trkB with brain‐derived neurotrophic factor (BDNF) and neurotrophin‐4/5 (NT‐4/5) and trkC with neurotrophin‐3 (NT‐3). By constructing 17 different chimeras and domain deletions of the human trk receptors and analyzing their binding affinities to the neurotrophins we have shown that an immunoglobulin‐like domain located adjacent to the transmembrane domain is the structural element that determines the interaction of neurotrophins with their receptors. Chimeras of trkC where this domain was exchanged for the homologous sequences from trkB or trkA gained high affinity binding to BDNF or NGF respectively, while deletion of this domain in trkC or trkA abolished binding to NT‐3 or NGF respectively. This domain alone retained affinities to neurotrophins similar to the full‐length receptors and when expressed on NIH 3T3 cells in fusion with the kinase domain showed neurotrophin‐dependent activation.

The neurotrophins form a highly homologous family of growth factors responsible for differentiation, survival, and function of neurons sensitive to their presence (reviewed in Ref.

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