Subepithelial B cells in the human palatine tonsil. II. Functional characterization

Mariella Dono, Simona Zupo, Adriano Augliera, Vito L. Burgio, Rosanna Massara, Andrea Melagrana, Mauro Costa, Carlo E. Grossi, Nicholas Chiorazzi, Manlio Ferrarini

Research output: Contribution to journalArticlepeer-review


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 FM 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 Ago 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.

Original languageEnglish
Pages (from-to)2043-2049
Number of pages7
JournalEuropean Journal of Immunology
Issue number9
Publication statusPublished - 1996


  • Extrafollicular
  • Palatine tonsil
  • Subepithelial B cell
  • T-independent antigen

ASJC Scopus subject areas

  • Immunology


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