CD27 and immune system disorder: 16 Warnatz Warnatz K K Denz Denz A A Drager Drager R R Braun Braun M M Groth Groth C C Wolff-Vorbeck Wolff-Vorbeck G G Severe deficiency of switched memory B-cells (CD27[+]IgM[–]IgD[–]) in subgroups of patients with common variable immunodeficiency: a new approach to classify a heterogeneous disease Severe deficiency of switched memory B-cells (CD27[+]IgM[–]IgD[–]) in subgroups of patients with common variable immunodeficiency: a new approach to classify a heterogeneous disease Blood.