The MHC class II ligand lymphocyte activation gene-3 is co-distributed with CD8 and CD3–TCR molecules after their engagement by mAb or peptide–MHC class I complexes

Abstract

Previous studies indicated that signaling through lymphocyte activation gene-3 (LAG-3), a MHC class II ligand, induced by multivalent anti-receptor antibodies led to unresponsiveness to TCR stimulation. Here, lateral distribution of the LAG-3 molecules and its topological relationship (mutual proximity) to the TCR, CD8, CD4, and MHC class I and II molecules were studied in the plasma membrane of activated human T cells in co-capping experiments and conventional fluorescence microscopy. Following TCR engagement by either TCR-specific mAb or MHC-peptide complex recognition in T-B cell conjugates, LAG-3 was found to be specifically associated with the CD3-TCR complex. Similarly, following CD8 engagement LAG-3 and CD8 were co-distributed on the cell surface while only a low percentage of CD4-capped cells displayed LAG-3 co-caps. In addition, LAG-3 was found to be associated with MHC class II (i.e. DR, DP and DQ) and partially with MHC class I molecules. The supramolecular assemblies described here between LAG-3, CD3, CD8 and MHC class II molecules may result from an organization in raft microdomains, a phenomenon known to regulate early events of T cell activation.

Maturation and Activation of Dendritic Cells Induced by Lymphocyte Activation Gene-3 (CD223)

“…LAG-3 (also termed CD223) is expressed in activated NK cells (19,24) and CD4 ϩ and CD8 ϩ T cells, where it is associated with the CD3/TCR complex at the cell surface (25,26). LAG-3, like CD4 (27,28), may oligomerize at the cell surface to interact more efficiently with class II (29).…”

“…They serve as platforms for signal transduction and, in clustering, form the TCR-APC contact junction, termed the immunological synapse. LAG-3 was found to be associated with the TCR (25,26) and to be constitutively present in plasma membrane lipid rafts extracted from human activated T cells based on their insolubility in Triton X-100 and low buoyant density in sucrose gradients (32). It was thus possible that in the TCR-APC contact junction LAG-3 and class II collaborate in establishing the clustering of raft platforms.…”

A Soluble Lymphocyte Activation Gene-3 Molecule Used as a Vaccine Adjuvant Elicits Greater Humoral and Cellular Immune Responses to Both Particulate and Soluble Antigens

“…LAG-3 is expressed in activated CD4 ϩ and CD8 ϩ T lymphocytes where it is associated with the CD3/TCR complex at the cell surface (3,4). LAG-3, like CD4 (5), may oligomerize at the cell surface to interact more efficiently with MHC class II molecules, as shown by the finding of three dominant negative mutations in the LAG-3 domain 1 that were able to inhibit the binding of wild-type LAG-3 molecules to class II molecules in a cell-cell adhesion assay (6).…”

MHC Class II Engagement by Its Ligand LAG-3 (CD223) Contributes to Melanoma Resistance to Apoptosis

“…Similar to CD4, LAG-3 oligomerizes at the surfaces of T cells and binds to MHC II on APCs but with significantly higher affinity than CD4 (15). LAG-3 is expressed on activated CD4 + and CD8 + T lymphocytes where it associates with the CD3-TCR complex at the cell surface (16,17) and negatively regulates signal transduction (18,19). As a consequence, it negatively regulates T cell proliferation, function, and homeostasis (14,20,21).…”