Major histocompatibility complex class II molecule and T-cell receptor (MHC class II and TCR)

The **major histocompatibility complex class II molecule (MHC class II)** is a cell-surface glycoprotein predominantly expressed on antigen-presenting cells such as dendritic cells, macrophages, and B cells. It presents processed peptide antigens to the **T-cell receptor (TCR)** on CD4+ T lymphocytes, a crucial interaction for activation of the adaptive immune system[1][4][5]. MHC class II molecules are encoded by HLA-DR, HLA-DP, and HLA-DQ loci in humans[6]. The T-cell receptor is a heterodimeric, membrane-bound glycoprotein (usually an αβ dimer) that recognizes peptides in the context of MHC class II or class I molecules, initiating signal transduction via the CD3 complex and resulting in T cell activation[2][5]. The combined recognition of peptide-MHC class II complexes by the TCR is central to immune surveillance, pathogen clearance, development of immune memory, and is involved in the pathogenesis of autoimmunity, graft rejection, and in the mechanisms of cancer immunosurveillance and immunotherapy[1][3][4]. Drugs that target this axis often modulate immune activity either by preventing T cell activation or by altering antigen presentation, but manipulation carries safety risks including immune suppression and triggering of unwanted immune reactions. **Note:** "MHC class II and T-cell receptor" is not a standard single molecular target; rather, it refers to an interacting ligand (MHC class II molecule) and a receptor (TCR) pair. Each is distinct but highly interdependent in biology and therapeutics. If structured data on individual molecules is required, separate entries for "Major histocompatibility complex class II molecule" and "T-cell receptor" are appropriate.

Other names

MHC-II and TCRMHC class II molecule and TCRMHC-II complex and T-cell receptorMHC class II/TCR complex

Inhibition of T-cell activation (e.g., blocking costimulation or peptide presentation) Modulation of antigen presentation (altering MHC class II peptide repertoire) Selective depletion or inactivation of T cells (e.g., antibody-mediated) Immune checkpoint modulation (enhanced or suppressed TCR signaling)