Interferon and phorbol esters down-regulate sIgM expression by independent pathways.
We studied the effects of recombinant interferon, 12-0-tetradecanoylphorbol-13-acetate (TPA), and phorbol 12, 13 dibutyrate (PDB) on surface immunoglobulin expression by Daudi cells. Incubation of cells with recombinant alpha 2 interferon (IFN-alpha 2) caused a 2.5-fold (60%) decrease in sIgM expression as measured by relative fluorescence index (RFI) using a flow cytometer. This decrease in sIgM expression was independent of inhibitory effects on proliferation and cell cycle progression. TPA or PDB also caused a threefold (67%) decrease in sIgM expression, while enhancing proliferation and cell cycle progression. Coincubation of cells with IFN-alpha 2 and TPA decreased sIgM expression by more than fourfold (greater than 75%), which was greater than the decrease induced by the optimal concentration of either agent alone. Molecular studies demonstrated that the treatment of cells with IFN-alpha 2 or TPA decreased the steady-state levels of mRNA for the heavy chain of IgM (c mu), suggesting that down-regulation of sIgM occurred at a pretranslational level. Activation of the cell membrane sodium/proton antiport did not play an integral role in the IFN-alpha 2 or phorbol-ester-induced pathway of sIgM down-regulation. Whereas IFN-alpha 2 induced an increase in the activity of 2',5'-oligoadenylate (2-5A) synthetase, the addition of TPA to IFN-alpha 2 caused a significant decrease in the activity of this enzyme. Although IFN-alpha 2 and TPA exhibited additive effects on sIgM expression, they had opposing effects on cell proliferation, cell cycle progression, and induction of 2-5A synthetase activity, suggesting that these agents down-regulate sIgM expression through independent pathways.
Schaffer
F M
FM
Division of Immunology, Hospital for Sick Children, Toronto, Canada.
Benedict
S H
SH
Petsche
D
D
Lau
A
A
Williams
B R
BR
Mills
G B
GB
Gelfand
E W
EW
D015088:2',5'-Oligoadenylate Synthetase / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D007075:Immunoglobulin M / Q000378:metabolism*; D007370:Interferon Type I / Q000494:pharmacology*; D008214:Lymphocytes / Q000166:cytology / Q000378:metabolism; D015240:Phorbol 12,13-Dibutyrate; D010703:Phorbol Esters / Q000494:pharmacology*; D014176:Protein Biosynthesis; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D013936:Thymidine / Q000378:metabolism
D002352:Carrier Proteins; D007075:Immunoglobulin M; D007370:Interferon Type I; D010703:Phorbol Esters; D011947:Receptors, Antigen, B-Cell; D017923:Sodium-Hydrogen Exchangers; D015240:Phorbol 12,13-Dibutyrate; D003513:Cycloheximide; D015088:2',5'-Oligoadenylate Synthetase; D013755:Tetradecanoylphorbol Acetate; D013936:Thymidine