SummaryHuman lymphocytes with natural killer (NK) activity, including most activated 3'/8 + T lymphocytes, recognize and lyse tumor target cells without requiring recognition of major histocompatibility complex antigen. However, unlike 3'/8 + T lymphocytes, NK cells do not express CD3/T cell receptor (TCR) molecules, and the receptors involved in ceU-mediated cytotoxicity are unknown. To further delineate circulating NK cells, we developed monoclonal antibodies (mAbs) against the human NK leukemia YT2C2. We report the isolation of a mAb termed BY55, recognizing at the cell surface a novel 80-kD protein with restricted expression, In addition to the immunizing cell line, this mAb binds to circulating NK cells, 3'/8* cells, and a minor subset of ot/B + T lymphocytes. Expression of the BY55 mAb-reactive epitope/ molecule is regulated by activation, as short-term culture of peripheral blood lymphocytes (PBL) with phorbol ester induced its downmodulation. Furthermore, BY55 mAb reactivity was found neither with the NK nor with the TCR a/B + and 3"/8 + clones tested. Biochemical studies as well as phenotypic analysis revealed that this structure is different from all previously identified molecules on the lymphocyte cell surface. Interestingly, we found that BY55 + cells exert most NK activity obtained with fresh circulating lymphocytes. We report that within fresh E rosette-positive PBL only a subset of the CD16 +, CD56 +, and CD57 + cells coexpressed BY55 molecule, indicating that BY55 mAb defines a unique subset mediating NK activity of circulating PBL.N 'K cells are circulating lymphocytes found within the large granular lymphocyte population (1, 2) and constitute, with CTL (3), the major cytotoxic effector lymphoid elements of the immune system. The characteristic surface markers expressed by NK cells are CD56 (4-6), CD57 (4, 5), CD16 (7-10), CD11b (11), and CDllc (11, 12). Most circulating cells with NK activity express the CD2 molecule but are distinct from the T lineage, as they do not express CD3 and do not rearrange any of the TCR genes (13, 14). In addition, NK cells mediate cytotoxicity without requiring recognition of MHC molecules on target cells. However, most activated TCR 3'/8 lymphocytes (15-18), and under certain circumstances some TCR o~/B cloned lymphocytes (19), can also mediate MHC-unrestricted cytotoxicity. The NK cell receptor(s) participating in target recognition remain(s) largely unknown despite extensive studies (20)(21)(22).In an attempt to define NK cell-specific surface structures, we characterized a mAb obtained by repeated immunization with YT2C2, a human cell line with NK functional characteristics. This cell line was selected for intermediate affinity binding of 12sI-IL-2 with the IL-2R p75 subunit (23). In the present study, we report the isolation ofa mAb, termed BY55, reacting at the cell surface with a novel 80-kD protein structure. BY55 mAb reactivity is observed with 15-25% of circulating lymphocytes. Two-color immunofluorescence staining of fresh E rosette-positive (E +) PBL o...
BCMA is a human gene expressed preferentially in mature B lymphocytes as a 1.2 kb mRNA, which encodes a 184 amino acid peptide (BCMAp). The study of BCMA mRNA expression, using human malignant B cell lines characteristic of different stages of B lymphocyte differentiation, demonstrated that the BCMA mRNA is absent in the pro-B lymphocyte stage. It is expressed faintly at the pre-B cell stage and its expression increases with B lymphocyte maturation. Polyclonal antibodies were used to show, by cellular fractionation and immunoprecipitation, that BCMAp is a non-glycosylated integral membrane protein. Furthermore, BCMAp inserts, in vitro, into canine microsomes, as a type I integral membrane protein. Cell surface labeling showed that BCMAp is not expressed in the plasma membrane of mature B lymphocytes. Immunofluorescence studies revealed that BCMAp lies in a cap-like structure near the nucleus, that was identified as the Golgi apparatus by co-localization of BCMAp with CTR433, a marker of the medial cisternae of the Golgi apparatus. Confocal scanning laser microscopy of U266 plasma cells labeled with markers of various Golgi apparatus subcompartments strongly suggests that BCMAp is located in the cis part of the Golgi apparatus. Thus, BCMAp is the first Golgi resident protein with a tissue specificity and whose expression is linked to the stage of differentiation of B lymphocytes. The location of BCMAp in the Golgi apparatus and its high expression in plasmocytes (secreting large amounts of Ig) suggest that BCMAp is implicated in the intracellular traffic of Ig.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.