Background The distribution of peripheral B cell subpopulations in SLE is unknown, although a variety of humoral abnormalities are known.
Objectives The phenotype and Ig heavy chain gene usage of peripheral B cell subpopulations of patients with active systemic lupus erythematosus (SLE) were examined.
Methods Peripheral B cells were characterised by FACS analysis and B cell subpopulations of one patient were characterised for V(D) J gene rearrangements.
Results In patients with SLE, there was a marked B lymphocytopenia that affected CD19+/CD27- naïve B cells more than CD19+/CD27+ memory B cells leading to a relative predominance of CD27 expressing peripheral B cells. In contrast, CD27high/CD38+/CD19dim/surface Iglow/CD20-/syndecan-1+plasma cells were found at an enhanced frequency in active but not inactive SLE patients. Upon immunosuppressive therapy, CD27high plasma cells and naïve CD27- B cells were markedly decreased in the peripheral blood. Mutational analysis of V gene rearrangements of individual B cells confirmed that CD27+ B cells coexpressing IgD were memory B cells preferentially using VH3 family members with multiple somatic mutations. CD27high plasma cells showed a similar degree of somatic hypermutation, but preferentially employed VH4 family members.
Conclusion These results indicate that there are profound abnormalities in the various B cell compartments in SLE that respond differently to immunosuppressive therapy.