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IMMUNOLOGY

ORIGINAL ARTICLE

Phenotypic and functional characterization of human CD25+ B cells

Mikael Brisslert, Maria Bokarewa, Pia Larsson, Kajsa Wing, L. Vincent Collins and Andrej Tarkowski
Department of Rheumatology and Inflammation Research, Sahlgrenska Academy at ˆ ˆ Goteborg University, Goteborg, Sweden

Summary We demonstrate that humans have a phenotypically and functionallydistinct subset of B lymphocytes that express the interleukin (IL)-2 receptor (IL-2R) a-chain, cluster of differentiation (CD) 25. We found that one-third of the circulating CD20+ B cells expressed CD25 and, using fluorescence-activated cell sorter (FACS) analysis, that these cells were significantly larger and more granulated than B cells not expressing CD25. The simultaneous expression of the othertwo subunits (CD122 and CD132) and the proliferative responses of cells expressing CD25 to IL-2 suggested that, in addition to CD25, functional IL-2 receptors were expressed on this cell population. CD25 expression on B cells was selectively up-regulated by Toll-like receptor 2 (TLR2), TLR4, and TLR9 ligands but not by a TLR3 ligand or Epstein–Barr virus (EBV) stimulation. Blockade of the nuclearfactor (NF)-jB pathway completely abolished CD25 up-regulation by these B cells. Interestingly, CD25+ B cells expressed significantly higher levels of surface immunoglobulins but lacked the ability to secrete immunoglobulin (Ig), as compared with CD25) B cells. Furthermore, CD25+ B cells performed significantly better as antigen-presenting cells in allogeneic mixed lymphocyte reactions (MLR), whichmay be a result of their expression of high levels of the costimulatory molecules CD27 and CD80. Finally, blocking of CD25 on B cells led to an almost total abrogation of MLR. Our results indicate that CD25+ B cells have distinct phenotypic and functional properties, including the ability to contribute to antigen presentation, which is linked to their expression of CD25. Finally, the differentialregulation of CD25 expression via selective TLR ligands suggests a role for CD25+ B cells in bridging innate and acquired immune responses. Keywords: B cells; CD25 expression, human; immunoregulation

doi:10.1111/j.1365-2567.2006.02331.x Received 12 September 2005; revised 9 December 2005; accepted 15 December 2005. Correspondence: Mikael Brisslert, Department of Rheumatology and InflammationResearch, Sahlgrenska ˆ Academy at Goteborg University, ˆ 41346 Goteborg, Sweden. Email: mikael.brisslert@rheuma.gu.se

Abbreviations: APC, allophycocyanin; BCIP, 5-bromo-4-chloro-indolylphosphate toulidine: BSA, bovine serum albumin; CD, cluster of differentiation; ConA, concavalin A; CpG-ODN, oligodeoxynucleotide that contains the CpG motif; poly(dI-dC), poly(deoxyinosine-deoxycytidine); EBV,Epstein–Barr virus; EDTA, ethylenediaminetetraacetic acid; EGTA, ethyleneglycolbis(2-aminoethylether)-N,N,N0 ,N0 -tetraecetic acid; ELISPOT, enzyme-linked immunosorbent spot assay; EMSA, electromobility shift assay; FACS, fluorescence-activated cell sorter; FCS, fetal calf serum; FITC, fluorescein isothiocyanate; GpC-ODN, oligodeoxynucleotide that contains the GpC motif; HEPES,N-(2-hydroxyethyl)piperazine-N0 -(2-ethanesulfonic acid) hemisodium; HLA, human leucocyte antigen; HSA, human serum albumin; Ig, immunoglobulin; IL, interleukin; LPS, lipopolysaccharide; mAb, monoclonal antibody; MFI, mean fluorescence intensity; MHC, major histocompatibility complex; MLR, mixed lymphocyte reaction; NF-jB, nuclear factor kappa B; NK, cell, natural killer cell; NTB, nitro-blue tetrazolium chloride;Pam3Cys, N-palmitoyl-S-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-[R]-cysteinyl-[S]-seryl-[S]-lysyl-[S]-lysyl-[S] -lysyl-[S]-lysine · 3 hydrochloric acid; PBMC, peripheral blood mononuclear cell; PBS, phosphate-buffered saline; PE, phycoerythrin; polyIC, polycytidylic-polyinosinic acid; PWM, pokeweed mitogen; SEB, staphylococcal enterotoxin B; TCR, T-cell receptor; TLR, Toll-like receptor. 548
Ó 2006...
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