The A7R34 monoclonal antibody reacts with mouse IL-7Rα also known as CD127. IL-7Rα is a 60-90 kDa type I transmembrane glycoprotein expressed on immature B cells, thymocytes, peripheral T cells, and bone marrow stromal cells. IL-7Rα forms a heterodimer with the common γ chain (γc or CD132) and upon ligation of IL-7 plays important roles in T and B cell development, and T cell homeostasis. Thymic Stromal Lymphopoietin (TSLP) also binds to IL-7Rα as a complex with the TSLPR chain to trigger activation of dendritic cells, and is also involved in B cell development, allergy and autoimmunity. The A7R34 antibody has been shown to block IL-7Rα signaling when administered in vivo.