CD1high B cells: a population of mixed origin

Abstract

A specialized subpopulation of T lymphocytes is reactive to the MHC class I-like molecule CD1d. It is not clear which cells are the major antigen-presenting cells in vivo in the activation of CD1-restricted immune responses. We have characterized a subset of B lymphocytes expressing six- to eightfold higher levels of CD1 than the bulk of B cells. The cells have a surface phenotype (CD21(high), CD23(low), IgM(high), IgD(low)) found previously to characterize B cells residing in the splenic marginal zones. CD1(high) B cells localize preferentially to the spleen, and appear late in ontogeny, at 3 - 4 weeks of age. The CD1(high) B cells were present in mice lacking conventional helper T cells, ruling out an exclusive origin from T cell-dependent immune responses. Still, some CD1(high) B cells had been involved in T cell-dependent immune responses as suggested by mutations in their rearranged immunoglobulin gene regions. The population could still be found in mice with severely reduced B cell reactivity to bacterial lipopplysaccharides (C3H / HeJ mice) and in mice unable to respond to thymus-independent type 2 antigens (NFR.Xid mice), as well as in germ-free mice, indicating that bacterial antigens are not major stimuli for the induction of CD1(high) B cells. In contrast, the CD1(high) B cell population was severely reduced in CD19-deficient mice. Taken together, the results imply that the CD1(high) population is heterogenous and of mixed origin, dependent for its development or maintenance on signaling through the CD19 molecule.

Resident enteric microbiota and CD8+ T cells shape the abundance of marginal zone B cells

“…4C and D). This agreed with the preservation of MZ B cells previously reported in GF rodents 17, 18. In contrast, MZ B cells were markedly decreased in RF mice in both percentage and absolute number, suggesting that the innate‐like B‐cell deficiency in RF mice was not due to the lack of products from their resident microbiota.…”

Human splenic marginal zone B cells lack expression of activation‐induced cytidine deaminase

“…However, it has also been shown that memory B cells of T cell‐dependent immune responses home to the MZ, indicating that the MZ B cell population in mice and rats is of mixed origin and function 32. The finding that about 90% of murine and rat MZ B cells carry unmutated V genes, while the remaining 10% are somatically mutated, is in line with this view of a mixed population 33, 34. In humans, the proportions of mutated and unmutated MZ B cells are reversed, with about 90% mutated and 10% unmutated cells 8, 13, 14.…”

PLCγ2 regulates Bcl‐2 levels and is required for survival rather than differentiation of marginal zone and follicular B cells

“…We have also observed a defect in MZ B cells in PLCγ2 –/– mice backcrossed onto a B10.BR background (data not shown). Since the size of the MZ B cell compartment varies considerably between mouse strains and with age 26, 27, we suggest that this may partly account for the discrepancy between the data from different laboratories. In addition, the levels and types of commensal microbial flora in the gut have been shown to influence the size of the MZ pool 28, and these doubtlessly vary between mouse facilities.…”