Lactoferrin Combined with Retinoic Acid Stimulates B1 Cells to Express IgA Isotype and Gut-homing Molecules.

It is well established that TGF-ß1 and retinoic acid (RA) cause IgA isotype switching in mice. We recently found that lactoferrin (LF) also has an activity of IgA isotype switching in spleen B cells. The present study explored the effect of LF on the Ig production by mouse peritoneal B cells. LF, like TGF-ß1, substantially increased IgA production in peritoneal B1 cells but little in peritoneal B2 cells. In contrast, LF increased IgG2b production in peritoneal B2 cells much more strongly than in peritoneal B1 cells. LF in combination with RA further enhanced the IgA production and, interestingly, this enhancement was restricted to IgA isotype and B1 cells. Similarly, the combination of the two molecules also led to expression of gut homing molecules α4ß7 and CCR9 on peritoneal B1 cells, but not on peritoneal B2 cells. Thus, these results indicate that LF and RA can contribute to gut IgA response through stimulating IgA isotype switching and expression of gut-homing molecules in peritoneal B1 cells.

Lactoferrin Combined with Retinoic Acid Stimulates B1 Cells to Express IgA Isotype and Gut-homing Molecules

It is well established that TGF-beta1 and retinoic acid (RA) cause IgA isotype switching in mice. We recently found that lactoferrin (LF) also has an activity of IgA isotype switching in spleen B cells. The present study explored the effect of LF on the Ig production by mouse peritoneal B cells. LF, like TGF-beta1, substantially increased IgA production in peritoneal B1 cells but little in peritoneal B2 cells. In contrast, LF increased IgG2b production in peritoneal B2 cells much more strongly than in peritoneal B1 cells. LF in combination with RA further enhanced the IgA production and, interestingly, this enhancement was restricted to IgA isotype and B1 cells. Similarly, the combination of the two molecules also led to expression of gut homing molecules alpha4beta7 and CCR9 on peritoneal B1 cells, but not on peritoneal B2 cells. Thus, these results indicate that LF and RA can contribute to gut IgA response through stimulating IgA isotype switching and expression of gut-homing molecules in peritoneal B1 cells.

B-1 Cells Differ from Conventional B (B-2) Cells: Difference in Proliferation

BACKGROUND: B-1 cells differ from conventional B-2 cells both phenotypically and functionally. The aim of this study was to investigate the difference between peritoneal B-1 cells and splenic B-2 cells in proliferation. METHODS: We obtained sorted B-1 cells from peritoneal fluid and B-2 cells from spleens of mice. During the culture of these cells, immunoglobulin secreted into the culture supernatants was evaluated by enzyme- linked immunosorbent assay. Entering of S phase in response to LPS-stimuli was measured by proliferative assay. RESULTS: Spontaneous Immunoglobulin M production occurred in peritoneal B-1 cells but not in splenic B-2 cells. LPS stimulated peritoneal B-1 cells secreted IgM at day 1, but splenic B-2 cells at day 2. In thymidine incorporation, peritoneal B-1 cells entered actively S phase after 24hours LPS-stimulation but splenic B-2 cells entered actively S phase after 48 hours. CONCLUSION: IgM secretion and S phase entering occurred early in peritoneal B-1 cells compared to splenic B-2 cells.