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Purification and properties of human B cell-activating factor.
Journal of Immunology (Baltimore, Md. : 1950)
|November 1, 1979
Summary
Human monocytes release a B-cell activating factor (BAF) that enhances the IgM response in T-cell depleted splenocytes. This study characterizes BAF
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Human monocytes produce factors that modulate immune responses.
- The IgM response of T-cell depleted murine splenocytes can be enhanced by specific factors.
Purpose of the Study:
- To characterize the biochemical properties of a monocyte-derived B-cell activating factor (BAF).
- To determine the molecular weight, isoelectric point, and stability of BAF.
Main Methods:
- Gel filtration
- Isoelectric focusing
- Ion exchange chromatography
- Isopycnic centrifugation
- Enzyme treatment (papain, trypsin, chymotrypsin)
Main Results:
- BAF is a molecule of approximately 15,000 daltons with an isoelectric point (pI) of 6.5.
- BAF exhibits a density of 1.33 g/ml and low solubility at low ionic strength.
- BAF is stable to acidic conditions, mild heating, and prolonged storage, but inactivated by alkali or boiling.
- Proteolytic enzyme treatments showed papain slightly reduced activity, while trypsin and chymotrypsin had no significant effect.
Conclusions:
- BAF is a distinct monokine with specific biochemical characteristics.
- The properties of BAF are consistent with other reported monokines of similar molecular weight.
- BAF plays a role in stimulating B-cell IgM responses.