Plasmacytoid dendritic cells are dispensable for non-infectious intestinal IgA responses in vivo.

Intestinal DCs orchestrate gut immune homeostasis by dampening proinflammatory T-cell responses and inducing anti-inflammatory IgA responses. Although no specific DC subset has been strictly assigned so far to govern IgA response, some candidate subsets emerge. In particular, plasmacytoid DCs (pDCs), which notoriously promote anti-viral immunity and T-cell tolerance to innocuous antigens (Ags), contribute to IgA induction in response to intestinal viral infection and promote T-cell-independent IgA responses in vitro. Here, using two transgenic mouse models, we show that neither short-term nor long-term pDC depletion alters IgA class switch recombination in Peyer's patches and frequency of IgA plasma cells in intestinal mucosa at steady state, even in the absence of T-cell help. In addition, pDCs are dispensable for induction of intestinal IgA plasma cells in response to oral immunization with T-cell-dependent or T-cell-independent Ags, and are not required for proliferation and IgA switch of Ag-specific B cells in GALT. These results show that pDCs are dispensable for noninfectious IgA responses, and suggest that various DC subsets may play redundant roles in the control of intestinal IgA responses.