The Human Marginal Zone B Cell

Abstract

This study describes the features of the marginal zone (MZ) B cells of human tonsils and spleens and compares them with those of the follicular mantle (FM) B cells from the same tissues. The two B cell subpopulations displayed marked differences in phenotype, in response capacity to T cell-independent antigens and polyclonal B cell activators, and in presentation of antigens to T cells. FM B cells expressed surface CD5, and hence should be considered as B1 cells by current nomenclature. Fractionation of MZ B cells according to the presence or absence of surface IgD revealed the presence of two subsets. These subsets were characterized by different properties, including the presence of Ig V(H) gene mutations and the response capacity to TI-2 antigens, this latter property being associated with IgD-positive cells. Comparison of the data with those reported for mice revealed that human MZ B cells had strong analogies with both the murine MZ and B1 cells. In contrast, human B1 cells (that is, CD5-positive FM cells) were considerably different, an observation that should prompt further studies. Indeed, B cells with characteristics analogous to those of murine B1 cells were detected in small but definite proportions in the peripheral blood and tonsils. If the current distinction into B1 and B2 cells has to be maintained also for humans, it is likely that only these CD5-positive cells rather than the FM B cells should be called B1 cells.

Fibromodulin, an extracellular matrix protein: characterization of its unique gene and protein expression in B-cell chronic lymphocytic leukemia and mantle cell lymphoma

“…Tonsil B cells similar to CLL cells do not have the propensity to undergo apoptosis. 57 Tonsil B cells may exhibit other survival factors, making fibromodulin redundant. The functional role of fibromodulin in the pathogenesis of B-CLL and MCL remains to be established.…”

KSHV infects a subset of human tonsillar B cells, driving proliferation and plasmablast differentiation

“…While we do not have direct experimental evidence to the contrary, recent descriptions of a newly defined B cell subset suggest an alternative hypothesis. This subset, termed IgM memory B cells, is present in the spleen, blood, and tonsil and shares phenotypic similarities with murine marginal zone B cells (64)(65)(66). IgM memory B cells provide an immediate line of defense against pathogens by rapidly proliferating and secreting antibody after stimulation by oral or blood-borne pathogens.…”

Immunoregulatory role for a public IgM idiotype in the induction of autoimmune diseases in Mycoplasma pneumoniae infection

“…This repertoire seems to be limited to IgM directed against self antigen that may play a role in homeostasis and tolerance [50][51][52]. The B subpopulation producing such antibodies seems not to enter the germinal centre, nor to be submitted to isotypic switch [53]. Indeed, 1D3 idiotope that we describe here seems to be limited to IgM class and not to undergo switch, probably due to a strong idiotypic/anti-idiotypic regulation, which is in agreement with the conservation at functional and phylogenic levels of this idiotope.…”