We have recently described a murine lymphocyte protein, provisionally termed sgp-60, which is expressed on virtually all lymphocytes of both T-and B-cell origin. A hamster monoclonal antibody to sgp-60 can inhibit interleukin-2 (IL-2) production, IL-2-receptor expression, and T-cell proliferation, events normally observed after stimulation of T cells with an antibody to the T-cell receptor/CD3 complex or with the lectin concanavalin A. Our previous studies did not reveal the molecular nature of the sgp-60 antigen. Purification of sgp-60 and protein sequencing demonstrate that sgp-60 is identical to the CD48 antigen, a ligand for the CD2 antigen, which is also called Blast-i in humans, BCM1 in mice, and OX-45 in rats. The identity of sgp-60 and CD48 was independently confirmed in gene transfection experiments. The antisgp-60 monoclonal antibody was selectively reactive with COS-7 ceUs transfected with a BCM1 cDNA clone but not with Kb-transfected controls. The results of the present report, together with our previous functional studies, may have implications for the role of CD2 and CD48 in murine T-cell activation.Antigen-specific CD4+ T inducer cells are critically involved in the generation of delayed-type hypersensitivity, antibody, and cytotoxic responses. Normally, CD4+ T cells are in a resting state. Most immune responses therefore depend on the prior activation of CD4+ T lymphocytes, their rapid proliferative expansion, and the lymphokines which they secrete (1).The activation of CD4+ T cells depends critically on cognate interactions of the T cell with an antigen-presenting cell (APC). Physiologic activation is imparted by a heterodimeric T-cell receptor (TCR) with specificity for antigenic peptides complexed to major histocompatibility complex (MHC) proteins. The TCR is associated with a set of nonvariable proteins, collectively termed CD3 (T3) (2). Besides the polypeptides forming the TCR/CD3 complex, a number of molecules participate in the T-cell activation process. Some function as cell-cell interaction molecules and some as signal-transducing elements, and some can serve both functions (2).We have recently described a murine glycoprotein, provisionally termed sgp-60, which is expressed on virtually all lymphocytes of both T-and B-cell origin (3-5). Antibody inhibition studies suggest a functional role for sgp-60 in CD4+ T lymphocytes: addition of the anti-sgp-60 monoclonal antibody (mAb) 5-8A10 or of its Fab fragment significantly inhibits the activation of purified T cells by the lectin Con A or by a mitogenic anti-CD3 mAb (3, 4). Proliferation, interleukin 2 (IL-2) production, IL-2 receptor expression, and generation of second messengers are all affected by the anti-sgp-60 mAb (3,4,6). Only a few antibodies affect T-cell function. Our experiments therefore suggest a role for sgp-60 in T-cell activation.Our previous studies did not reveal the molecular identity of the sgp-60 antigen. In the present report, we close this gap. Partial amino acid sequence of the sgp-60 antigen and gene transfe...
We have recently identified a novel murine glycoprotein termed sgp-60, which is expressed on the cell surface of T and B lymphocytes. Because of the profound modulatory effects of sgp-60 on activation through the T cell receptor/CD3 complex, we have examined the membrane attachment domain of the molecule. sgp-60 is not expressed on the surface of variants of a T-T hybridoma cell line that are defective in glycosylphosphatidylinositol (GPI) anchor biosynthesis. In wild-type but not in mutant cells, sgp-60 can be labeled with palmitic acid. Furthermore, the molecule can be removed from the cell surface of both T and B lymphocytes by enzymatic digestion with a phosphatidylinositol-specific phospholipase C. We conclude that the sgp-60 molecule is linked to the plasma membrane via a GPI anchor.
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.