Antibody

An antibody is a protein made by B cells that binds a specific antigen. This binding can neutralize the target or mark it for removal by immune defenses.

Antigen-binding site: The variable region of an antibody that makes direct contact with an antigen. Its shape and chemistry determine which molecular features the antibody recognizes.
B cell: A lymphocyte that can develop into an antibody-secreting plasma cell or a memory B cell. B cells produce antibodies and undergo selection during adaptive immune responses.
Monoclonal antibody: An antibody preparation whose molecules share one antigen specificity and arise from a single B-cell lineage. Monoclonal antibodies can be designed or selected to target specific molecules in disease.
Immunoglobulin M: An antibody class often secreted as a pentamer during early immune responses. Its multimeric structure gives it high overall binding strength and efficient complement activation.
Immunological memory: The capacity of adaptive immunity to respond more rapidly or effectively after prior exposure to an antigen. Memory B cells can produce antibodies quickly during later encounters with the same target.
Immunoglobulin domain: A compact protein fold found in antibodies and other immune-system proteins. Repeated domains form antibody chains and provide their characteristic structure.
Antigen: A molecule or molecular feature recognized by an antibody or immune receptor. Antibodies bind specific antigen features, called epitopes.
Polyclonal antibody: A mixture of antibodies that recognize multiple epitopes, typically produced by different B-cell clones. Unlike a monoclonal preparation, it can bind several sites on the same antigen.
Immunoglobulin G: The most abundant antibody class in blood, with several roles in systemic immunity. It illustrates the long-lived, versatile antibody responses often associated with class switching.
Antibody-dependent cellular cytotoxicity: The killing of antibody-coated target cells by immune cells, especially natural killer cells. Antibodies can recruit killer cells through their constant regions.

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