β-catenin is a 92 kDa intracellular protein that binds to the cytoplasmic tail of E-cadherin to mediate cellular adhesion. In addition, it is a key downstream effector in the Wnt signaling pathway. In the absence of Wnt binding its receptor, β-catenin is phosphorylated and resides in the cytoplasm, where it is eventually targeted for degradation by ubiquitination. Upon Wnt binding, β-catenin becomes dephosphorylated, translocates to the nucleus and modulates gene expression in partnership with the transcription factors T cell factor (TCF) and lymphocyte enhancer binding factor (LEF). Expression of β-catenin is found in a wide variety of nonimmune and immune tissues, including thymocytes and T and B lymphocytes. Clone D13A1 recognizes endogenous β-catenin protein only when residues Ser33, Ser37 and Thr41 are not phosphorylated.