CD27 and systemic lupus erythematosus: However, the latest research reveals that DN B cells in SLE patients are mainly characterized by the lack of C-X-C chemokine receptor type 5 (CXCR5), the follicular homing marker, characterized by CD19+IgD-CD27-CXCR5-, defined as DN2 B cells, and seem to hold an immunopathogenic role in the onset of disease.