The LG.3A10 antibody reacts with CD27, a 45 – 55 kDa member of the tumor necrosis factor receptor superfamily. CD27 is found on peripheral T cells, memory B cells, and NK cells and in mice has been found on most thymocytes, except CD46-CD8- precursors. CD27 and its ligand CD70 are involved in multiple aspects of T cell biology, including the costimulation and expansion of CD4+ and CD8+ T cells and differentiation to memory CD8+ T cells. CD27 interacts with TRAF family members, resulting in enhanced cellular proliferation and the induction of anti-apoptotic proteins. Additionally, CD27 plays important roles in T cell – B cell interactions and the maturation of effector T cells. The expansion of activated B cells and their differentiation to plasma cells is also reported to be enhanced by CD27.