Evidence That Glycoprotein 96 (B2), a Stress Protein, Functions as a Th2-Specific Costimulatory Molecule

Abstract

After the engagement of Ag receptor, most of the Th cells for their optimal activation require a second (costimulatory) signal provided by the APCs. We demonstrate the isolation and characterization of a 99- to 105-kDa protein (B2), from LPS-activated B cell surface, and its function as a Th2-specific costimulatory molecule. Appearance of B2 as a single entity on two-dimensional gel electrophoresis and as a distinct peak in reverse-phase HPLC ascertains the fact that B2 is homogeneous in preparation. Electron microscopy as well as competitive binding studies reveal that 125I-labeled B2 specifically binds anti-CD3-activated T cell surface and also competes with its unlabeled form. Internal amino acid sequences of B2 are found to be identical with stress protein gp96. The identity of B2 as gp96 is also revealed by immunological characterization and by confocal microscopic colocalization studies of B2 and gp96 on LPS-activated B cells. Confocal imaging studies also demonstrate that gp96 can be induced on B cell surface without association of MHC molecules. Furthermore, the novel role of gp96 in Th cell proliferation skewing its differentiation toward Th2 phenotype has also been established. Ab-mediated blocking of gp96-induced signaling not only abrogates in vitro proliferation of CD4+ T cells, but also diminishes the secretion of Th2-specific cytokines. Notably, the expression of CD91 (receptor of gp96/B2) is up-regulated on anti-CD3-activated Th cells and also found to be present on Th1 and Th2 subsets.

The stress protein gp96 is not an activator of resting rat bone marrow–derived dendritic cells, but is a costimulator and activator of CD3+ T cells

“…These findings, to some extent at least, confirm a previous study that reported gp96 acts as a Th2-specific costimulatory molecule (Banerjee et al 2002). The receptors and signaling events underlying these effects are currently under investigation, as are the in vivo immunoregulatory consequences of high-dose gp96 administration.…”

“…In this regard, a number of investigators have reported that gp96 induces the maturation of, and cytokine secretion from, these and other APCs and increases their capacity to stimulate the proliferation of T cells (Basu et al 2000;Singh-Jasuja et al 2000a;Zheng et al 2001;Baker-LePain et al 2002;Reed et al 2003). Gp96 might also have direct effects on T cells because a protein expressed on the surface of lipopolysaccharide (LPS)-activated B cells (B2), which has been identified as gp96, has been reported to act as a T-helper 2 (Th2)-specific costimulatory molecule for murine splenic T cells (Banerjee et al 2002).…”

Essential role of CD91 in re-presentation of gp96-chaperoned peptides

“…In independent studies, Habich et al (15) reported that ␣ 2 M competes with gp96 for binding macrophage, as does gp96 itself. Banerjee et al (16) showed that Th cells express CD91 on the cell surface and that gp96 binds CD91 on the T helper (Th) cell surface. Such binding is abrogated by anti-CD91 Abs but not control Abs.…”

Natural Killer andNK-LikeT-Cell Activation in Colorectal Carcinoma Patients Treated with Autologous Tumor-Derived Heat Shock Protein 96

“…The possibility that HSP96 or other members of the HSP family may directly interact with lymphocytes is also supported by recent data reporting the binding of HSP96 and HSP70 to murine CD4 + T lymphocytes (37) or human NK cells (38) 5 However, other receptors, such as CD94, TLR2, and TLR4, which have been found to mediate HSP70 binding to NK cells (38,40) or to be up-regulated in CD56 + NK and T cells on virus or parasite infection (41,42), could also play a role in this phenomenon.…”