An immunoglobulin which will bind with the antigen against which it was directed.
Antigen
Any molecule capable of producing an immune response.
Antigen Presenting Cell (APC)
Cells that process antigen and display a fragment on the cell surface in association with the MHC (major histocompatibility complex).
B Cell
Cells of the the adaptive immune system that express cell surface immunoglobulins specific for an epitope on an antigen.
Epitopes
A specific region of an antigen that is recognized by B cells or T cells.
Heavy Chain
The part of an immunoglobulin that determines to which of five classes that it belongs and have a variable region and a constant region.
IgA
An immunoglobulin whose heavy chains are "alpha", and is found primarily in mucosal regions of the body.
IgD
An antibody whose heavy chain is "delta".
IgE
An antibody whose heavy chains are "epsilon" and is associated with mast cells (tissue basophils).
IgG
An antibody whose heavy chain is "gamma" and which is associated with the specific secondary humoral response in inflammation.
IgM
An antibody whose heavy chains are "beta" and are a major part of the primary specific humoral response in inflammation.
Immunogen
Any substance capable of generating an immune response.
Immunoglobulin
The more precise name for the proteins called antibodies, which migrate in the gamma globulin region in a protein electrophoresis.
Light Chain
The portion of an immunoglobulin that is attached to its heavy chains by means of disulfide bonds, and is of either "kappa" or "lambda" type.
Monoclonal Antibodies
Antibodies that are specific for one epitope.
Opsonins
A molecule that attaches to a microbe or other antigen to facilitate its recognition by phagocytic cells.
Opsonization
The attachment process of an opsonin to an antigen.
Phagocytosis
The process by which antigens are engulfed and destroyed.
Polyclonal Antibodies
A mixture of non-identical antibodies which are directed against more than one epitope, even if they are specific for a particular antigen or organism.
Variable Region
The portion of the heavy and light chains of an immunoglobulin that consists of amino acid sequences that are unique for each antibody, and provide its specificity to its corresponding antigen.