CD21/35 promotes protective immunity to Streptococcus pneumoniae through a complement-independent but CD19-dependent pathway that regulates PD-1 expression.
Haas KM, Poe JC, Tedder TF. CD21/35 promotes protective immunity to Streptococcus pneumoniae through a complement-independent but CD19-dependent pathway that regulates PD-1 expression. J Immunol. 2009 Sep 15; 183(6):3661-71.