Which mechanism explains background staining in adipose tissue during IHC?

• A. Hydrophobic interactions only.
• B. Ionic interactions only.
• C. Hydrophobic and ionic interactions between immunoglobulins and lipoid substances in fatty tissue.
• D. Hydrogen bonding.

Answer: (C)

Background staining in fat tissue comes from the way antibodies can interact with the lipid-rich, non-polar environment of adipocytes. Immunoglobulins can bind non-specifically to the lipid droplets through hydrophobic interactions, since the lipid-packed areas are largely non-polar. At the same time, there are charged lipid components and associated proteins that can engage in ionic (electrostatic) interactions with parts of the antibody. These two types of non-specific contacts together explain why adipose tissue often shows background signal. Hydrogen bonding plays a smaller role here because the lipid-dense environment is largely non-polar, making hydrophobic and ionic interactions the dominant mechanisms.