Description: This J3-129 monoclonal antibody reacts with human CD19, a 95-kDa transmembrane glycoprotein. CD19 is expressed by B cells during all stages of development, excluding terminally differentiated plasma cells. However, follicular dendritic cells express CD19. CD21, CD81, Leu13, MHC class II, and CD19 together form a multi-molecular complex that associates with the B cell receptor. Signaling through CD19 induces tyrosine phosphorylation, calcium flux and B cell proliferation.