Fig. 5: Retinoic acid-producing dendritic cells facilitate the differentiation of IgA + B lymphocytes within Peyer’s patches.
From: The role of retinoic acid in the production of immunoglobulin A
Specialized microfold cells (M cells) transport microbes and luminal antigens to intestinal retinoic acid-producing dendritic cells (RA-DCs). These RA-DCs present antigenic peptides on major histocompatibility complex-2 (MHCII) to T lymphocytes, promoting their differentiation into T-helper 2 (Th2) cells. Th2 cells express CD40 ligand, which further activates B cells that have recognized their cognate antigen with the B cell receptor (BCR). Moreover, Th2 cells secrete multiple cytokines, including interleukin-4 (IL4), to facilitate B cell activation. Within PPs, the most predominant mechanism of IgA differentiation in B cells involves TD activation. It is suggested that local RA-DCs together with CD40 costimulation provided by T cells skew naïve B cells into an IgA isotype. Additionally, a fraction of TI IgA induction is also reported within PPs, but whether this requires the involvement of RA is still unclear.
