PDCA Expression by B Lymphocytes Reveals Important Functional Attributes

We have demonstrated in this study the existence of a PDCA-expressing functional B cell population (PDCA(+) B lymphocytes), which differentiates from activated conventional B (PDCA(-)IgM(+)) lymphocytes. Stimulation with anti-mu, LIPS, CpG oligodeoxynucleotide, HSV-1, or CTLA-4 Ig activates the PDCA(+) B lymphocytes, leading to cell division and induction of type I IFNs and IDO. Notably, the PDCA(+) B lymphocytes are capable of Ag-specific Ab production and Ig class switching, which is corroborated by transfer experiments in B- and PDCA(+) B lymphocyte-deficient mu MT mice. Importantly, in lupus-prone MRL-Fas(lpr) mice, PDCA(+) B lymphocytes remain the principal source of autoantibodies. The PDCA(+) B lymphocytes have phenotypes with plasmacytoid dendritic cells, but are a distinct cell population in that they develop from C-kit(+)B220(+) pro-B precursors. Thus, our data suggest that not all PDCA(+) cells are dendritic cell-derived plasmacytoid dendritic cells and that a significant majority is the PDCA(+) B lymphocyte population having distinct phenotype and function. The Journal of Immunology, 2010, 184: 807-815.