Isotype control IgG refers to antibodies that are identical in isotype (e.g., IgG) and subclass (e.g., IgG1, IgG2) to the primary antibody used in an experiment but are directed against an irrelevant antigen. Their primary purpose is to assess the level of non-specific binding that may occur during the experimental process. This helps researchers determine whether observed signals are due to specific interactions with the target antigen or if they arise from background noise caused by non-specific binding.

Characteristics of Isotype Control IgG

To effectively serve as a control, isotype IgG must match several key characteristics of the primary antibody:

• Host Species: The control must be derived from the same species as the primary antibody (e.g., mouse).
• Isotype and Subclass: It should match the immunoglobulin class (e.g., IgG) and subclass (e.g., IgG1, IgG2) of the primary antibody to ensure similar binding properties.
• Conjugation Type: If the primary antibody is conjugated to a fluorophore or enzyme for detection, the control must be conjugated in the same manner.

These characteristics ensure that any non-specific binding observed with the control can be accurately compared to that of the primary antibody.

Mechanism of Action

Isotype control IgG functions by providing a baseline measurement for non-specific binding in assays. When researchers stain cells or tissues with both a primary antibody and its corresponding isotype control, they can compare fluorescence or signal intensity between the two. The difference indicates specific binding due to the primary antibody, while any similarity suggests non-specific interactions.