B cell receptors and MHC molecules

The B-cell receptor is a multi-chain complex on the surface of B lymphocytes, responsible for antigen recognition and initiation of immune signaling. Its extracellular component is a membrane-bound immunoglobulin; its intracellular signaling is mediated primarily by accessory proteins Igα and Igβ, which contain ITAM motifs phosphorylated during activation[5]. The B-cell receptor is central to humoral immunity and facilitates the production of antibodies upon antigen binding. Major histocompatibility complex (MHC) molecules are glycoproteins found on cell surfaces; they present processed peptide fragments to T cells, enabling immune recognition. MHC class I is expressed on all nucleated cells and presents endogenous peptides to CD8+ T cells; MHC class II is primarily expressed on antigen-presenting cells and presents exogenous peptides to CD4+ helper T cells[3][4][1]. MHC molecules are highly polymorphic and crucial for transplant compatibility, immunity against pathogens, and susceptibility to autoimmune diseases. Note: Grouping "B cell receptors and MHC molecules" as a single therapeutic target is structurally and functionally incorrect—they are two distinct entities with coordinated, yet fundamentally different, roles in immune response[3][5]. For most therapeutic and biomarker applications, analyses should treat each as a separate target.

Other names

Immunoglobulin receptorsIg (surface immunoglobulin)HLA (human leukocyte antigen, in humans)

B-cell receptors (BCR) function through antibody binding and antigen recognition, leading to downstream phosphorylation via ITAMs in Igα and Igβ, activating or inhibiting B cell functions. Major Histocompatibility Complex (MHC) molecules present peptide antigens to T cells, thereby triggering T cell-mediated immunity.