Preferential Generation of Follicular B Helper T Cells from Foxp3+ T Cells in Gut Peyer's Patches

Most of the immunoglobulin A (IgA) in the gut is generated by B cells in the germinal centers of Peyer's patches through a process that requires the presence of CD4(+) follicular B helper T (T-FH) cells. The nature of these T-FH cells in Peyer's patches has been elusive. Here, we demonstrate that suppressive Foxp3(+)CD4(+) T cells can differentiate into T-FH cells in mouse Peyer's patches. The conversion of Foxp3(+) T cells into T-FH cells requires the loss of Foxp3 expression and subsequent interaction with B cells. Thus, environmental cues present in gut Peyer's patches promote the selective differentiation of distinct helper T cell subsets, such as T-FH cells.