Abstract

Next to conventional B cells (or B-2 cells), peritoneal B-1 cells have been shown to contribute significantly to the production of IgA-secreting plasma cells in the gut. Evidence for this was mainly based on studies comprising manipulated animals, including lethally X-irradiated and transgenic mice. To examine the ability of peritoneal B-1 cells from untreated mice to switch actively to IgA in vivo, we performed RT-PCR analysis on FACS-sorted peritoneal B-cell subsets from untreated BALB/c mice in order to examine the presence of germline Cα mRNA and mature Cα mRNA transcripts. Germline Cα and mature Cα transcripts were readily detectable in peritoneal B-1 cells (defined as IgMbright/IgDdull), but not, or very little, in peritoneal B-2 cells (defined as IgMdull/IgDbright). Moreover, by subdividing the B-l-cell population in CD5+ B-1a cells and CD5- B-1b cells, it was shown that in vivo expression of germline Cα and mature Cα transcripts was largely restricted to the B-1b-cell lineage. These results indicate that peritoneal B-1 cells indeed are capable to switch to IgA under normal physiological conditions and hereby further support the view that B-1 cells contribute significantly to the mucosal IgA response, albeit this function appears to be restricted to the B-1b-cell subset.

Highlights

  • The intestinal lamina propria is characterized by a mucosal preponderance of IgA-secreting plasma cells (Van der Heijden et al, 1987)

  • The cells expand, differentiate, and mature into IgA-secreting plasma cells (Tseng, 1984). Another source of progenitor cells that contribute to the pool of lamina propria IgA plasma cells is formed by B-1 cells (Kroese et al, 1989, 1995), which reside abundantly in the murine peritoneal cavity (Herzenberg et al, 1986)

  • The presence of germline Cce mRNA transcripts and mature IgA heavy-chain mRNA transcripts was determined by RT-PCR in unsorted peritoneal cells from 3-month-old untreated BALB/c mice. cDNA was synthesized from mRNA extractions of peritoneal washout cells as well from unsorted Peyer’s patch cells, which already have been shown to express Cce and mature IgA transcripts (Weinstein et al, 1991)

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Summary

Introduction

The intestinal lamina propria is characterized by a mucosal preponderance of IgA-secreting plasma cells (Van der Heijden et al, 1987). To study the ability of peritoneal B-1 cells (both Bl a and B-lb) to switch to IgA under normal physiological conditions, we sorted peritoneal B-cell subpopulations from untreated BALB/c mice and examined those populations for the presence of germline IgA transcripts and full-length IgA mRNA transcripts. The presence of germline Cce mRNA transcripts and mature IgA heavy-chain mRNA transcripts was determined by RT-PCR in unsorted peritoneal cells from 3-month-old untreated BALB/c mice.

Results
Conclusion

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