CD40LG and lymphoproliferative syndrome: Moreover, the rise in sCD23 levels during the postpartum period suggests the resumption of B‐cell differentiation into memory B cells, also supported by our previous results.5 Interestingly, in patients with rheumatoid arthritis undergoing rituximab therapy, we (ML and GC) have previously found that rises in sCD23 levels were highly associated with relapse and coincided with the increased production of IgM rheumatoid factor and serum FLC release.28 Elevated concentrations of these fragments have also been frequently associated with inflammatory or lymphoproliferative disorders.44, 45