Title: Subepithelial B cells in the human palatine tonsil. II. Functional characterization
Abstract: Abstract This study investigates the main functional features of subepithelial (SE) B cells and compares them with those of purified germinal center (GC) and follicular mantle (FM) B cells isolated from the same tonsils. Unlike GC B cells, SE B cells failed to produce polyspecific antibodies in vitro ; unlike GC B cells, SE B cells expressed high levels of Bcl‐2 and failed to undergo spontaneous apoptosis in vitro . The most striking function of SE B cells was their ability to produce IgM antibodies to T cell‐independent type‐2 (TI‐2) (but not to TI‐1) antigens (Ag). These antibodies could not be detected when both FM and GC B cells were stimulated with TI‐2 Ag in vitro . Moreover, B cells isolated from peripheral blood were unable to mount a response to TI‐2 Ag. The latter finding is consistent with the observation that B cells with the phenotypic features of SE B cells were virtually absent in the peripheral blood and emphasizes the notion that SE B cells belong to a subset of non‐recirculating B cells. SE B cells were by far superior to FM B cells in mixed lymphocyte reaction (MLR) stimulation of allogeneic T cells in vitro , although they were not as efficient as dendritic cells (DC). In order to stimulate T cells efficiently, SE B cells had to be exposed to anti‐μ antibody, a treatment which induced expression of activation markers such as CD80, CD86, CD69 and CD39, usually absent in resting SE B cells. CD80 and CD86 molecules expressed by SE B cells participated in the chain of events required to promote the proliferation of allogeneic T cells as demonstrated by inhibition tests with the appropriate mAb. The expression of CD80 and CD86 by anti‐μ‐treated SE B cells was not, however, the sole explanation for their good antigen presenting capacities since the exposure of FM B cells to anti‐μ antibody also induced expression of these surface structures. Nevertheless, these cells failed to become good MLR stimulators. Collectively, the above data contribute further to the characterization of a distinct subset of tonsillar B cells which resemble, both phenotypically and functionally, the B cells of the splenic marginal zone.
Publication Year: 1996
Publication Date: 1996-09-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 35
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