Physical association between the CD8 and HLA class I molecules on the surface of activated human T lymphocytes.

Abstract

Immune recognition by cytotoxic effector T cells requires participation of the CD8 and major histocompatibility complex class I antigens. We found that the CD8 molecule is noncovalently associated with the HLA class I heavy chain on the surface of human T cells activated by Con A. Accordingly, anti-CD8 monoclonal antibodies precipitated a heterodimer containing polypeptides of32 and 43 kDa from the lysates of activated T cells. tigen and polymorphic MHC determinants (5-8). This recognition appears to be a complex process, and at least one additional cell surface component, the CD8 molecule, is implicated (4, 9-11). CD8 has been characterized as a 32-to 34-kDa integral membrane protein in its reduced form (12,13). Under nonreducing conditions, CD8 has been identified in a series of multimeric forms differing in inter-or intrachain disulfide bonding (13). Studies have suggested (1-4, 14-16) that CD8 can bind to MHC class I molecules and thereby increase T-cell-target or T-cell-accessory-cell avidity that allows recognition of antigen and T-cell activation. To date, however, the actual physical interaction between CD8 and MHC class I molecules on T-cell surface is not well understood. This report demonstrates a noncovalent association between CD8 and HLA heavy chain molecules on the surface of activated human T cells.MATERIALS AND METHODS Cells. Human thymocytes and peripheral blood T cells isolated by forming rosettes with sheep erythrocytes (17) were used directly for radioiodination. For Con A activation, T cells were incubated at 106 cells per ml with 10' non-T cells per ml in complete medium [RPMI 1640 medium with 5% (vol/vol) fetal bovine serum, glutamine (0.06 mg/ml), streptomycin (100 tg/ml), and penicillin (100 units/ml)] with Con A (10 pkg/ml) for 2 days. Before radioiodination, the Con A-activated T cells were washed once with 50 mM a-methyl mannoside (Sigma) and twice with isotonic phosphatebuffered saline (pH 7.2). For allogeneic activation of T cells, unseparated peripheral blood lymphocytes from two healthy donors were incubated in complete medium at 2 x 106 cells per ml for 5 days. A natural killer (NK)-enriched cell population obtained by discontinuous Percoll gradient centrifugation (18) was 80% positive for CD16, recognized by monoclonal antibody B73.1 (19). A cloned CTL line (CD3 +, CD4 -, CD8 '), derived from peripheral blood lymphocytes sensitized with irradiated allogeneic non-T cells, was maintained in RPMI 1640 medium with 20% (vol/vol) pooled human AB serum (Flow Laboratories) and human interleukin 2 (20 units/ml) (Boehringer Mannheim). The human T-cell leukemia line HPB-ALL was from J. Minowada (Roswell Park Memorial Institute, Buffalo, NY) and was maintained in complete medium.Antibodies. The monoclonal antibodies OKT8A (Ortho Diagnostics), anti-Leu-2a (Becton Dickinson), and C8 (20) (a gift of C. Y. Wang, United Biomedical, Lake Success, NY) recognize CD8. The anti-HLA-A, -B, and -C monoclonal antibodies W6/32 (21) and A1.4 (22) The publication costs of this article were defr...

Misfolding of Major Histocompatibility Complex Class I Molecules in Activated T Cells Allows cis-Interactions with Receptors and Signaling Molecules and Is Associated with Tyrosine Phosphorylation

“…Moreover, we have demonstrated that the temporal co-existence of two conformational states allows misfolded MHC-I molecules to associate with other molecules and receptors, such as CD8␣␤. Early studies reporting the physical association between CD8␣␤ and MHC-I molecules used crosslinking reagents and antibodies against the CD8␣ chain (20,21). In our studies we also used anti-CD8␣ antibodies, and the levels of co-precipitated MHC-I molecules were very similar to these earlier studies even in the absence of cross-linking reagents.…”

HLA-C is the inhibitory ligand that determines dominant resistance to lysis by NK1- and NK2-specific natural killer cells.

“…This model is supported by previous detection of class I-associated molecules, including peptide hormone receptors (insulin and epidermal growth factor receptors) (29)(30)(31), CD25 (32), and CD8 (33 ----cr--v -Aw68, and -B27 suggest that these residues are located in the peptide binding cleft of HLA-C and, more specifically, in or near the F pocket, which binds the C-terminal amino acid residue of a peptide nonamer (34). Thus, HLA-C may bind peptides capable of mediating NK inhibition.…”

Clustering of Class I HLA Oligomers with CD8 and TCR: Three-Dimensional Models Based on Fluorescence Resonance Energy Transfer and Crystallographic Data

“…It was also demonstrated that CD8 molecules could increase the apparent affinity of MHC-peptide ligands for the TCR (49,50). Earlier works definitely supported the close cooperation and molecular proximity of peptide-MHC and CD8 (51), also at the interface of target and effector cells probed directly by intercellular FRET measurements between Ag-presenting and effector cells (47). Considering the CD8-class I HLA interaction, the present model of HLA tetramer was further expanded with the 3D structural entities of the connecting CD8 and TCR molecules.…”