The proximity ligation assay differs from other antibody-based in situ applications by the use of two antibodies (rather than a single antibody). The use of two antibodies against different epitopes of the same protein results in increased assay specificity. In addition, use of two antibodies against different proteins allows both localization and quantification of protein-protein interactions. The unique amplification of signal provided by the detection steps provides a unique capability to study both stable and transient interactions at endogenous expression levels of the target protein(s). Paired with various image-capture & analysis systems, the proximity ligation assay is highly amenable to high-throughput, cell-based screens. Please refer to the PROTOCOL section of our website for additional information involving development and trouble-shooting for the proximity ligation assay.