Anti-Taq antibody binds Taq polymerase and inhibits its activity until the reaction temperature is elevated. At that point, the Taq antibody is denatured and releases its hold on Taq polymerase, allowing DNA synthesis to proceed.
The binding of a Taq antibody to Taq polymerase is the premise of hot-start PCR. By preventing Taq polymerase activity until the dentauration step of PCR is underway, nonspecific amplification due to mispriming and/or formation of primer dimers during PCR assembly is prevented. As a result, experimental background is significantly decreased and reaction specificity is increased.