Two distinctive pathways for recruitment of naïve and primed IgM⁺B cells to the gut lamina propria

Delivery strategies to enhance oral vaccination against enteric infections

“…1). Thus specific DC populations and local factors result in preferential generation of IgA-producing B cells in the GALT and MLNs and imprinting of lymphocytes with the specific gut homing receptors α4β7 integrin, CCR9 and CCR10 [66,71]. In support of the idea of a common mucosal immune system, lung DCs have also been shown to be capable of imprinting a GIT homing phenotype on T cells allowing for their migration to the gut where they facilitated protection against an intestinal Salmonella infection [79].…”

“…As in the case of PPs, a follicle associated epithelium with M cells is present on the lumen facing side of ILFs. Uptake of pathogens including S. typhimurium, leads to the formation of germinal centers (GCs) in mature ILFs [64][65][66]. Interestingly, it was found that the presence or absence of GCs in ILFs did not influence the active class switching of naïve B cells to active IgA secreting B cells [67].…”

“…Once primed, lymphocytes exit the PPs and the MLNs via the thoracic duct and blood and finally migrate back to the gut via homing receptors and cognate ligands expressed only in the gut tissue. The integrin α4β7 allows lymphocytes to specifically attach to the mucosal addressin, cell adhesion molecule-1 (MADCAM-1) [74,80] expressed on endothelial cells of the post capillary venules in the gut lamina propria (LP) thus guiding lymphocytes toward these key gut effector sites [66]. The chemokine receptors CCR9 and CCR10 allow lymphocyte homing to the small or large intestine where endothelial cells produce CCL25 and CCL28 respectively, adding further gut homing specificity [81,82].…”

The regulation of IgA class switching

“…Although still debated 130 , the presence of IgA CSR in the lamina propria is in agreement with compelling evidence showing that CSR is not restricted to lymphoid follicles, but also occurs in extrafollicular lymphoid areas 131 , including subepithelial areas 99 . In both mice and humans, lamina-propria-derived IgA CSRinducing signals may target multiple IgM + B-cell subsets that originate from various sites, including the peritoneum, mucosal follicles and bone marrow 26,31,73,129,132 . A full characterization of these IgM + B-cell subsets is made more difficult by the fact that they may rapidly modify their phenotype on entering the microenvironment of the lamina propria.…”

Villous B Cells of the Small Intestine Are Specialized for Invariant NK T Cell Dependence

“…Due to the dependence of NF-B-interacting kinase in LT␤R signaling, SLP B cells would seem to be distinguished from the IgM ϩ lamina propria population that forms in aly/aly mice, a strain naturally deficient in this kinase (26) A novel feature shared by SLP (this study) and ILF (18) B cells is their reduced formation in the absence of cognate Ag receptor function. In this study, we also show that their formation was substantially reduced in Btk Ϫ/Ϫ and G␣i2 Ϫ/Ϫ mice.…”