Fig. 7: Retinoic acid-producing dendritic cells facilitate the differentiation of IgA + B lymphocytes within isolated lymphoid follicles in a T cell-independent fashion.
From: The role of retinoic acid in the production of immunoglobulin A
B cell activation within isolated lymphoid follicles (ILFs) is accomplished via multiple steps. Retinoic acid (RA)-producing dendritic cells (RA-DCs) retrieve antigens from microfold cells, which is necessary for B cell receptor (BCR) antigen recognition by B cells. Simultaneously, naïve B cells are stimulated via toll-like receptors (TLRs) and cofactors in the form of BAFF and APRIL produced by tolerogenic DCs and the epithelium. Secondary stimuli are produced after TLR5 activation by tolerogenic DCs. As a result, gut DCs secrete interleukin-4 (IL4), interleukin-5 (IL5) and RA to skew naïve B cells into an IgA isotype. Upon subsequent maturation, B lymphocytes leave the ILFs to become IgA-secreting plasma cells within the lamina propria (LP).
