Prominent role for plasmacytoid dendritic cells in mucosal T cell-independent IgA induction

Hiroyuki Tezuka. et al. immunity. 2011; 34, 247-257

Speaker: Nai-Chi Yeh (葉乃綺)                                      Time: 13:00~14:00, Jun. 1, 2011

Commentator: Dr. Ching-Chuan Liu (劉清泉醫師)       Place: Room 601

Abstract

In our body, naïve B cells would undergo class switch recombination (CSR) to secrete multiple classes of immunoglobulin (Ig) isotypes. There are two different mechanisms of CSR, one is T cell-dependent (TD), and the other is T cell-independent (TI). In this study, the authors wanted to know what kind of cells and molecules induce naïve B cells undergo IgA CSR in the gut-associated lymphoid tissues (GALT). They observed that naïve B cell can express the Aicda gene, a critical enzyme of CSR, and produce IgA at the absence of T cell in the mesenteric lymph nodes (MLNs). They discovered that the plasmacytoid dendritic cells (pDCs), which expression of membrane-bound APRIL and BAFF, induced substantially higher amounts of IgA than the conventional dendritic cells (cDCs). In addition, pCD-induced IgA production was markedly reduced when the TACI-Ig and BCMA-Ig, which blocks the binding of APRIL and BAFF to their corresponding receptors, exist. Then, they detected that type I IFNs play an important role in the expressions of APRIL and BAFF of pDCs. When culturing naïve B cells with the pDCs lacking the type I INF receptor, the IgA production was significantly reduced, and this phenomenon was restored by the addition of APRIL or BAFF. Finally, they found that the stromal cells in MLN can release high amounts of type I IFNs, which could induce pDCs express membrane-bound APRIL and BAFF, then promote naïve B cells to undergo the IgA CSR.

References

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2.      Tezuka H, et al. Prominent role for plasmacytoid dendritic cells in mucosal T cell-independent IgA induction. Immunity. 2011;25;34(2):247-57

3.      Tangye SG. Plasmacytoid DCs induce gutsy plasma cells. Immunity. 2011 Feb 25;34(2):144-6.