Immunoglobulin

An immunoglobulin is a protein family whose members include antibodies and B-cell receptors. Its characteristic domains form regions that bind antigens or support immune-cell signaling.

Immunoglobulin domain: A compact protein domain found in immunoglobulins and many other immune-system proteins. Repeated immunoglobulin domains build the molecule’s binding arms and constant regions.
Antigen: A molecule or molecular structure that can be specifically recognized by an antibody or immune receptor. Immunoglobulin binding depends on molecular features presented by an antigen.
Monoclonal antibody: An antibody population produced from a single clone and directed against one target specificity. Monoclonal antibodies use immunoglobulin structure for targeted diagnosis and treatment.
T-cell receptor: A receptor on T cells that recognizes peptide antigens presented by major histocompatibility complex molecules. It shares an immunoglobulin-like domain fold but is not an immunoglobulin.
Antibody: A soluble immune protein that binds a specific antigen and can help neutralize or eliminate it. Antibodies are secreted immunoglobulins that act independently of B cells.
Complementarity-determining region: A highly variable segment of an antibody or receptor that directly contributes to antigen binding. These loops form much of the immunoglobulin surface that contacts antigen.
Enzyme-linked immunosorbent assay: A plate-based assay that uses enzyme-linked reagents to detect or quantify molecules such as antibodies or antigens. Immunoglobulin binding provides the specific recognition step in many ELISA formats.
Immunoglobulin G: The most abundant antibody class in human blood, with roles in neutralization and immune effector activity. IgG is one specific class within the broader immunoglobulin family.
B-cell receptor: A membrane-bound receptor complex on B cells that recognizes antigen and initiates cellular signaling. The B-cell receptor is an immunoglobulin form displayed on the cell surface.
V(D)J recombination: A DNA rearrangement process that assembles variable gene segments to generate diverse antigen receptors. It creates the varied immunoglobulin variable regions used by developing B cells.

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