Control of lymphocyte function through CD27-CD70 interactions

In contrast to the expression of other TNFR/TNF family members, expression of CD27 and its ligand CD70 is predominantly confined to lymphocytes. High expression levels of CD27 appear to be dependent on proper ligation of anti gen receptors, whereas for the induction of CD70 expression additional (co- stimulatory and/or pro-inflammatory.) signals are required. Next to membran e-bound CD27 also a soluble form of CD27 is produced in the course of the i mmune response. Soluble CD27 (sCD27) is found in body fluids and can be use d to monitor local and systemic immune activation. lit addition, elevated s erum concentrations of sCD27 are found in patients with B cell malignancies and levels of sCD27 strongly correlate with tumor load. Based on functiona l experiments and in vitro expression regulation data, we propose that inte ractions between. activated lymphocytes in vivo can result in CD27-CD70 int eractions that may regulate the size and function of antigen-primed lymphoc yte populations.