Lee Y, Haas KM, Gor DO, Ding X, Karp DR, Greenspan NS, Poe JC, Tedder TF. Complement component C3d-antigen complexes can either augment or inhibit B lymphocyte activation and humoral immunity in mice depending on the degree of CD21/CD19 complex engagement. J Immunol. 2005 Dec 15; 175(12):8011-23.