Anti-mu treatment suppresses immunoglobulin light-chain gene expression and Peyer's patch development

Antibody is required for protection against virulent but not attenuated Salmonella enterica serovar typhimurium

Resolution of infection with attenuated Salmonella is an active process that requires CD4(+) T cells. Here, we demonstrate that costimulation via the surface molecule CD28, but not antibody production by B cells, is required for clearance of attenuated aroA Salmonella enterica serovar typhimurium. In contrast, specific antibody is critical for vaccine-induced protection against virulent bacteria. Therefore, CD28(+) CD4(+) T cells are sufficient for clearance of avirulent Salmonella in naive hosts, whereas CD4(+) T cells and specific antibodies are required for protection from virulent Salmonella in immune hosts.

Isolation of peritoneal precursors of B-1 cells in the adult mouse

Two weeks of daily peritoneopheresis of adult mice result in the selective depletion of B-1 cells, followed by the appearance of a population of B220+IgM-lymphocytes in the peritoneal cavity. These cells share with bone marrow (BM) pre-B cells expression of lambda 5, VpreB, and RAG-1 genes and a higher fraction of unrearranged V to DJ heavy (H) chain immunoglobulin (Ig) gene segments, when compared with mature B lymphocytes. Upon transfer to SCID recipients, sorted peritoneal B220+IgM- cells fail to colonize the BM, repopulate very few B cells in the spleen, but entirely reconstitute the B-1 cell compartment in the peritoneal and pleuropericardial cavities. In contrast, parallel transfers of sorted BM and pleuropericardial cavities. In contrast, parallel transfers of sorted BM B220+IgM- cells result in reconstitution of the BM and spleen B lineage cell compartments, but in no coelomic B cell repopulation. Both types of pre-B cells reconstitute splenic plasma cells of donor origin, but with markedly distinct efficiencies: the ratio of IgM-plasma cell/B cell numbers in the spleens of peritoneal pre-B cell recipients is more than 500-fold higher than that of recipients reconstituted by BM pre-B cells. We take these data to indicate that (1) differentiative commitment to the B-1 cell population occurs before selection events on mature cells; (2) B-1 precursors exist or may be locally produced in the adult mouse; (3) there is a lineage-related differential ability of mature B cells to undergo terminal differentiation to high-rate Ig secretion.

Effect of anti-Ig on rabbit B cell function and Ig expression

We have examined the effect which xenogeneic anti-Ig has on rabbit B cell function and Ig expression in an effort to understand the phenomenon of antibody mediated suppression. Treatment of rabbit lymphocyte cultures with xenogeneic anti-rabbit Ig causes 2.5-3.8 fold decrease in the level of Ig secreting cells with little or no long-term effect on surface Ig. This suppression in B cell secretory function is not the result of suppression of Ig gene expression since xenogeneic anti-rabbit Ig treatment causes a 1.7-2.7 fold increase in Ig L and H chain mRNA levels. Collectively, these data are consistent with the hypothesis that antibody mediated suppression of B cell function occurs at a post-transcriptional level involving either the secretory pathway of Ig expression and/or blockage in B cell differentiation.