Differential transport requirements of HLA and H-2 class I glycoproteins

Abstract

Transport of human and mouse major histocompatibility complex class I glycoproteins has been examined in a transport deficient B-lymphoblastoid cell line X T-lymphoblastoid cell line (B-LCL X T-LCL) hybrid, 174 X CEM.T2 (T2). This cell line expresses no detectable endogenous HLA-B5 and reduced levels of HLA-A2 on its surface although these molecules are synthesized. In order to study this defect further, either HLA-Bw58 or HLA-B7 genomic clones were transfected into T2. Metabolic labeling and immune precipitation demonstrated biosynthesis of the Bw58 or B7 glycoprotein. However, like the endogenous HLA-B5 molecule, neither HLA-Bw58 nor HLA-B7 was expressed at the cell surface. The cloned genes were properly expressed on the surface of C1R, a control B-LCL. To determine if mouse class I alleles had the same transport requirements as the human class I glycoproteins, either mouse H-2Dp or H-2Kb class I genes were introduced into T2. Surprisingly, the H-2 class I glycoproteins were transported to the cell surface normally. These data suggest a fundamental difference between human and mouse histocompatibility antigens in their requirements for intracellular transport.

Tapasin-Mediated Retention and Optimization of Peptide Ligands During the Assembly of Class I Molecules

“…H-2K b is expressed at high levels on the surface of the human TAP-deficient cell line T2, yet it is retained in the ER of the TAPdeficient mouse cell line RMA-S (24,25). This discrepant behavior of H-2K b in human and murine cells may reflect, in part, greater stabilization of K b complexed to human ␤ 2 m relative to K b complexed to murine ␤ 2 m. Therefore, we anticipated that H-2K b would also be expressed on the surface of human cells deficient in tapasin even though H-2K b is expressed at low levels (ϳ15% of wild-type levels) in tapasin knockout mice (A. G. Grandea, unpublished observations; and Ref.…”

“…Thus, murine class I molecules are expressed at high levels when transfected into human APC, whereas some HLA molecules require cotransfection of human ␤ 2 m to permit high levels of surface expression (24). However, in mutant APC there are certain anomalies that remain unexplained.…”

“…However, in mutant APC there are certain anomalies that remain unexplained. For example, the murine H-2K b molecule is expressed on the cell surface of the TAP-deficient human cell line T2, despite failure of TAP-dependent peptide loading (24). This contrasts markedly with the retention of K b in the ER of murine RMA-S cells lacking a functional TAP complex (25).…”

MHC Class I Presentation of Live and Heat‐Inactivated Sendai Virus Antigen in T2Kb Cells Depends on an Intracellular Compartment with Endosomal Characteristics

“…T2 cells are derived from the parental T1 cell line, and have a large deletion in the MHC class II region including genes for the TAP1/2 and LMP2/7 products [30]. T2 cells transfected with H-2K b are designated T2K b [31]. All target cells were cultured in RPMI 1640 medium supplemented with 5% FCS, L-glutamine, penicillin and streptomycin.…”

Conversion of In Vitro Cultured Human Monocytes into Effective Presenters of an HER2/neu‐Encoded CTL Peptide Epitope

“…The presence of these surface markers indicated that the cells cultured by our method fell within accepted criteria used to define purified, classical dendritic cells. Previous investigations have employed the T2 Ag-processing mutant [25,26] to identify CTL epitopes relevant for melanoma [see, for example, References 31,32] and ovarian carcinoma [21,22]. Expression of CD40, CD80 and CD86 costimulatory proteins, HLA-DR (class II), and ICAM-1, ICAM-3 and LFA-3 classical intercellular adhesion proteins, on the surface of DC-like cells prompted a comparative analysis between T2 and DC-like cells for their ability to elicit TNF-a release from anti-ovarian carcinoma CTL.…”