Fc Region
Definition
The crystallisable fragment of an antibody, formed by the paired constant domains of the two heavy chains. The Fc region mediates effector functions including complement activation (IgG, IgM) and binding to Fc receptors on phagocytes, and determines the immunoglobulin class.
- Location
- Constant domains of two heavy chains
- Function
- Complement activation, Fc receptor binding
- Determines
- Immunoglobulin class
Common questions
How does the Fc region differ functionally from the Fab region of the same antibody?+
The Fab region, formed by the variable domains, is what binds the specific antigen. The Fc region does not touch the antigen at all; instead it recruits the immune system's effector mechanisms, complement proteins and phagocytic cells, once the Fab has already made the antigen recognition.
Why does the Fc region matter for forensic serology work specifically?+
Because it determines antibody class (IgG, IgM, IgA, etc.), the Fc region underlies class-specific immunoassays used to identify body fluids, such as tests that rely on class-specific secondary antibodies binding a fluid-specific antigen-antibody complex.
Related terms
- Affinity
- The binding strength of a single antigen-binding site for one epitope, expressed as the equilibrium dissociation constant (Kd). A lower Kd indicates...
- Complementarity-Determining Regions (CDRs)
- Six hypervariable loops, three in the heavy-chain variable domain and three in the light-chain variable domain, that together form the antigen-binding site....
- Cross-Reactivity
- The capacity of an antibody raised against one analyte to bind structurally related compounds. In RIA, cross-reactivity is the main driver of...
- Fab Fragment
- The antigen-binding fragment of an antibody, consisting of one complete light chain paired with the variable and first constant domain of a...
- Monoclonal Antibody (mAb)
- An antibody produced by a single hybridoma clone, so that every molecule in the preparation is identical, targets the same epitope, and...