Peritoneal and splenic B‐1 cells are separable by phenotypic, functional, and transcriptomic characteristics

Abstract

B-1 cells constitute a distinct B cell population with unique phenotypic and functional characteristics. Although the origin of B-1 cells remains controversial, B-1 cells in different locations are generally considered to be part of the same pool. To determine the validity of this assumption, we examined peritoneal and splenic B-1 cells isolated by flow cytometric cell sorting from normal mice for several features. We found that splenic B-1 cells differ from peritoneal B-1 cells in terms of surface antigen expression, viability ex vivo, immunoglobulin secretion in vitro, stimulated cell cycle progression, and expression of Notch family, Notchdependent, and Notch-associated genes. These results indicate that splenic and peritoneal B-1 cells are not the same and thus dispute the notion that B-1 cells are uniform, and may suggest that different subpopulations of B-1 cells arise separately, home individually, and/or are heavily influenced by local environmental factors.

Peritoneal B‐2 cells comprise a distinct B‐2 cell population with B‐1b‐like characteristics

“…4 and depict the means of four independent experiments. We found that the majority of splenic B-2 cells did not survive 3 days in culture, as expected [23], with 36 AE 2.8% (mean AE SEM, n = 4) viability at the end of the incubation. In contrast, peritoneal B-1 cells remained largely viable over the entire culture period (76 AE 6.2%), also as expected [23].…”

“…We found that the majority of splenic B-2 cells did not survive 3 days in culture, as expected [23], with 36 AE 2.8% (mean AE SEM, n = 4) viability at the end of the incubation. In contrast, peritoneal B-1 cells remained largely viable over the entire culture period (76 AE 6.2%), also as expected [23]. In addition to enhanced survival, B-1 cells spontaneously secrete IgM when placed in culture for several days [29].…”

“…Splenic B-1 cells differ from peritoneal B-1 cells in many characteristics, including lack of constitutively activated STAT3 and IL-10 mRNA expression, and failure to respond to PMA [22]. Unlike peritoneal B-1 cells, splenic B-1 cells do not survive well in vitro, nor do they spontaneously secrete IgM [23]. Further, in a transgenic mouse model, splenic B-1 cells were shown to differ from their peritoneal counterparts in antibody repertoire [24].…”

Reciprocal generation of Th1/Th17 and Treg cells by B1 and B2 B cells

“…2D). In contrast, although CD80 expression on B1p cells is greatly increased over that of B2s cells [19], anti-CD80 antibody had much less effect on the capacity of B1p cells to stimulate alloreactive T cells than did anti-CD86 antibody (Fig. 2C) and failed to reverse the poor iT reg induction by B1p and B2p cells (Fig.…”

“…To test this, blocking antibodies for CD80 and CD86 were added during iT reg induction. Although CD86 expression on B1p cells is only modestly increased over that of B2s cells [19], anti-CD86 antibody markedly reduced the capacity of B1p (and B2p) cells to stimulate alloreactive T cells (Fig. 2C); conversely, anti-CD86 antibody dramatically increased the capacity of B1p (and B2p) cells to convert Foxp3 -CD4 + T cells to the Foxp3 + phenotype (Fig.…”