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Human native soluble CD40L is a biologically active trimer, processed inside microsomes
F Pietravalle1, S Lecoanet-Henchoz, H Blasey
1Glaxo Institute for Molecular Biology, Geneva, Switzerland.
Insights
Soluble CD40 ligand (CD40L), a protein involved in immune responses, is shed from T cells. This soluble form, when combined with interleukin-4, promotes B cell proliferation.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- CD40 ligand (CD40L) is crucial for B cell activation, mediating proliferation, adhesion, and immunoglobulin class switching upon binding to its receptor CD40.
- CD40L is expressed on activated T cells and other immune cells.
Purpose of the Study:
- To identify and characterize soluble cleavage products of human CD40L.
- To investigate the processing and function of soluble CD40L.
Main Methods:
- Stimulation of human T cell clones and collection of supernatant.
- Subcellular fractionation to analyze CD40L processing.
- Biochemical characterization of soluble CD40L (e.g., trimeric structure).
- In vitro assays to assess the effect of soluble CD40L on B cell proliferation, often in combination with interleukin-4.
Main Results:
- Soluble CD40L cleavage products were identified in the supernatant of stimulated T cells.
- Transmembrane CD40L processing occurs within microsomes and is dependent on cell stimulation.
- Native soluble human CD40L exists as a trimer.
- Soluble CD40L, with interleukin-4, effectively induces B cell proliferation.
Conclusions:
- CD40L undergoes stimulation-dependent cleavage, releasing soluble forms.
- Soluble CD40L retains biological activity, capable of inducing B cell proliferation.
- Understanding CD40L processing and function is important for immune regulation research.
Abstract:
CD40 ligand (CD40L) is a glycoprotein expressed on the surface of activated helper T cells, basophils, mast cells, and eosinophils. Binding of CD40L to its receptor CD40 on the B cell surface induces B cell proliferation, adhesion, and immunoglobulin class switching. We have identified soluble cleavage products of human CD40L in the supernatant of a stimulated human T cell clone. Subcellular fractionation experiments have shown that the transmembrane CD40L is processed inside the microsomes and that its cleavage is stimulation-dependent. The native human soluble CD40L is trimeric and, when used in conjunction with interleukin-4, induces B cell proliferation.