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A novel anti-apoptosis serum factor that down-regulates fas-mediated apoptosis
H Kikuchi1, S Sugiyama, S Imajoh-Ohmi
1Institute of Medical Science, University of Tokyo.
Abstract:
The Fas antigen (CD95) is a receptor for apoptotic cell death signals. Human T Jurkat cells that express the Fas molecule on the cell surface are sensitive to cytotoxic anti-Fas monoclonal antibodies (mAbs). We report here that fetal calf serum (FCS) contains a novel factor (SAF: Serum Anti-Apoptosis Factor) that suppresses Fas-mediated apoptosis of Jurkat cells. The apoptotic cell death of Jurkat cells induced by an anti-Fas mAb was accelerated when FCS was removed from the medium. Depletion of serum itself did not induce apoptosis without the mAb. The apoptosis-suppressing activity was not seen in neonatal calf or adult bovine serum, suggesting that the SAF activity was developmentally regulated. The anti-apoptosis activity was not detected in any fraction of FCS obtained on gel filtration chromatography. However, the activity was recovered in a certain fraction on the addition of calf serum, suggesting that the anti-apoptotic activity of SAF requires other serum factor(s). We purified SAF from FCS using an assay system reconstituted with calf serum, and raised antibodies (Abs) to it in rabbits. The anti-SAF Ab inhibited the apoptosis-suppressing activity, indicating that SAF is a key factor for the anti-apoptotic activity of FCS.
Insights
Fetal calf serum contains a novel Serum Anti-Apoptosis Factor (SAF) that suppresses Fas-mediated apoptosis in Jurkat cells. This factor
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Fas antigen (CD95) mediates apoptotic cell death signals.
- Human T Jurkat cells are sensitive to anti-Fas monoclonal antibodies (mAbs).
Purpose of the Study:
- To identify and characterize factors in fetal calf serum (FCS) that modulate Fas-mediated apoptosis.
- To investigate the role of serum components in regulating T-cell apoptosis.
Main Methods:
- Jurkat cells were treated with anti-Fas mAbs with or without FCS.
- FCS was fractionated using gel filtration chromatography.
- Serum Anti-Apoptosis Factor (SAF) was purified from FCS.
- Antibodies (Abs) against SAF were generated and tested for inhibitory activity.
Main Results:
- FCS suppressed Fas-mediated apoptosis of Jurkat cells.
- Removal of FCS accelerated anti-Fas mAb-induced apoptosis.
- SAF activity was developmentally regulated and required other serum factors for detection.
- Purified SAF and anti-SAF Abs confirmed SAF's role in suppressing apoptosis.
Conclusions:
- Fetal calf serum contains a novel Serum Anti-Apoptosis Factor (SAF).
- SAF is a key component of FCS that suppresses Fas-mediated apoptosis in T cells.
- SAF's activity is developmentally regulated and may depend on interactions with other serum components.