What Is A Secondary Antibody?

Immunolabeling is critical for many areas of basic or clinical research to detect specific cell or tissue components (antigens) in a sample. This approach can be performed with direct and indirect methods by generating antigen-specific antibodies and fusing tags to antibodies.

For direct immunolabeling, the primary antibody is conjugated to a tag and directly binds to the antigen of interest. The indirect approach involves a conjugated secondary antibody that binds indirectly to the target antigen by binding to the antigen-specific primary antibody.

Secondary antibodies are generated and harvested by immunizing a host animal with an antibody from another species. For example, if the primary antibody is a rabbit polyclonal antibody, an anti-rabbit secondary antibody is raised in a different host species such as goat. The produced secondary antibody's specificity is dependent on the immunizing antibody's characteristics, such as species, subclass, fragment, etc.