authors request that the following corrections be noted. It was accidentally stated that the studies by Kajita et al. (1) and Lee et al. (2) dealt with cinnamoyl-CoA reductase modified plants when in fact they concerned 4-coumarate:coenzyme A ligase (4CL) transgenic plants. Lignin concentration was reduced by down-regulation of 4CL activity in both studies (1, 2). In a subsequent article, Kajita et al. (3) reported a negligible decrease in lignin concentration and a decreased syringyl-toguaiacyl ratio for lignin composition of a sense-suppressed 4CL transgenic tobacco line. Kajita et al. (1) rather than Kajita et al. (3) was inadvertently cited when this later report was contrasted with the large decreases in lignin concentration and an increased syringyl-to-guaiacyl lignin ratio for anti-sense suppressed 4CL Arabidopsis transgenics (2). The authors apologize for the confusion these errors have created for readers of their Commentary and to the authors of the cited work for misrepresenting their research. November 10, 1998, of Proc. Natl. Acad. Sci. USA (95, 13612-13617), the authors request that the following correction be noted: In Fig. 2 appearing on page 13614, the genotype identification for testicular histology in panels C and D were shown reversed. The correct identification is Ϫ͞Ϫ for panel C and ϩ͞ϩ for panel D. The fifth sentence of the figure legend should read as follows: "Histological sections at lower (E) and higher (D) magnification of the seminiferous tubuli from a wild-type and mutant (F and C) mouse."Cell Biology. In the article "Efficient construction of a large nonimmune phage antibody library: The production of highaffinity human single-chain antibodies to protein antigens" by

We have developed a technetium labeling technology based on a new organometallic chemistry, which involves simple mixing of the novel reagent, a 99m Tc(I)-carbonyl compound, with a His-tagged recombinant protein. This method obviates the labeling of unpaired engineered cysteines, which frequently create problems in large-scale expression and storage of disulfide-containing proteins. In this study, we labeled antibody single-chain Fv fragments to high specific activities (90 mCi/mg), and the label was very stable to serum and all other challenges tested. The pharmacokinetic characteristics were indistinguishable from iodinated scFv fragments, and thus scFV fragments labeled by the new method will be suitable for biodistribution studies. This novel labeling method should be applicable not only to diagnostic imaging with 99mTc, but also to radioimmunotherapy approaches with 186/188 Re, and its use can be easily extended to almost any recombinant protein or synthetic peptide.

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For treatment of patients with prostate cancer (PCa), we developed a novel T cell-engaging (BiTE) antibody designated AMG 212 or BAY2010112 that is bispecific for prostate-specific membrane antigen (PSMA) and the CD3 epsilon subunit of the T cell receptor complex.

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SummaryPlant-based expression systems are attractive for the large-scale production of pharmaceutical proteins. However, glycoproteins require particular attention as inherent differences in the N-glycosylation pathways of plants and mammals result in the production of glycoproteins bearing core-xylose and core-α (1,3)-fucose glyco-epitopes. For treatments requiring large quantities of repeatedly administered glycoproteins, the immunological properties of these non-mammalian glycans are a concern. Recombinant glycoproteins could be retained within the endoplasmic reticulum (ER) to prevent such glycan modifications occurring in the late Golgi compartment. Therefore, we analysed cPIPP, a mouse / human chimeric IgG1 antibody binding to the β -subunit of human chorionic gonadotropin (hCG), fused to a C-terminal KDEL sequence, to investigate the efficiency of ER retrieval and the consequences in terms of N-glycosylation. The KDEL-tagged cPIPP antibody was expressed in transgenic tobacco plants or Agrobacterium -infiltrated tobacco and winter cherry leaves. N-Glycan analysis showed that the resulting plantibodies contained only high-mannose (Man)-type Man-6 to Man-9 oligosaccharides. In contrast, the cPIPP antibody lacking the KDEL sequence was found to carry complex N-glycans containing core-xylose and core-α (1,3)-fucose, thereby demonstrating the secretion competence of the antibody. Furthermore, fusion of KDEL to the diabody derivative of PIPP, which contains an N-glycosylation site within the heavy chain variable domain, also resulted in a molecule lacking complex glycans. The complete absence of xylose and fucose residues clearly shows that the KDEL-mediated ER retrieval of cPIPP or its diabody derivative is efficient in preventing the formation of non-mammalian complex oligosaccharides.

Recombinant TCRs confer specificity to T cells and trigger their activation. Receptors with Ab-derived binding domains have the advantages of MHC-independent Ag recognition and of targeting a variety of chemically different molecules. We explored the impact of the position of a defined epitope within the target molecule on the efficacy of receptor-mediated T cell activation. T cells were grafted with recombinant immunoreceptors that recognize either the membrane distal N or the proximal A3 domain of carcinoembryonic Ag (CEA). Upon binding to isolated, solid-phase immobilized CEA, receptor-mediated T cell activation correlates with the binding efficiency, irrespectively, of the epitope position. Upon binding to CEA expressed on the cell membrane, in contrast, the A3 epitope mediates more efficiently T cell activation than the N epitope, although the N epitope is bound with higher affinity. The CEA N epitope when expressed in a more membrane proximal position, however, activated receptor grafted T cells with higher efficiency than in the distal position. The position of the targeted epitope within the molecule obviously has major impact on the efficacy of T cell activation independently of the binding efficiency of the immunoreceptor.

Passive immunization with recombinant HCG-specific antibodies may have clinical utility as (i) diagnostic and therapeutic tools for HCG-expressing cancers and (ii) contraceptive measures.