Activation and activation-induced death of human tonsillar B cells and Burkitt lymphoma cells: lack of CD95 (Fas/APO-1) ligand expression and function.
Activation of T cells was shown to up-regulate the Fas ligand (FasL) which binds to the CD95 (APO-1/Fas) antigen and mediates activation-induced cell death (AICD) of activated T cells and T lymphoma cells. A recent report showed that mouse B cells express the FasL upon activation with lipopolysaccharide (LPS). We therefore asked whether activation of human B cells induces expression of FasL and whether AICD is mediated, as in T cells, through autocrine production of the FasL. We used human tonsillar B cells and Burkitt lymphoma cell lines which were activated by CD40 ligand, surface (s)IgM cross-linking, or LPS. Northern and Western blot analysis failed to detect FasL during B cell activation or AICD of both normal and malignant B cells. Low-level expression of FasL was detected by reverse transcriptase-polymerase chain reaction. Functional experiments, however, showed that FasL is not functionally expressed upon activation. IgM-mediated AICD in the tonsillar or Burkitt lymphoma B cells could not be inhibited by FasL blocking. Thus, our data show that, in contrast to T cells, activation of normal or malignant human B cells does not lead to functional FasL expression.
Daniel
P T
PT
Max Delbrück Center for Molecular Medicine, Berlin, Germany. pdaniel@orion.rz.mdc-berlin.de
Oettinger
U
U
Mapara
M Y
MY
Bommert
K
K
Bargou
R
R
Dörken
B
B
D017209:Apoptosis / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D002051:Burkitt Lymphoma / Q000276:immunology*; D018920:Coculture Techniques; D053222:Fas Ligand Protein; D006801:Humans; D019169:Jurkat Cells; D008024:Ligands; D008213:Lymphocyte Activation; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000502:physiology*; D014066:Palatine Tonsil / Q000166:cytology / Q000276:immunology; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000096:biosynthesis* / Q000502:physiology*
C505661:FASLG protein, human; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D008024:Ligands; D008562:Membrane Glycoproteins; D019014:fas Receptor