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Research Article Free access | 10.1172/JCI117089
Division of Immunology, Children's Hospital, Boston, Massachusetts.
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Division of Immunology, Children's Hospital, Boston, Massachusetts.
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Division of Immunology, Children's Hospital, Boston, Massachusetts.
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Division of Immunology, Children's Hospital, Boston, Massachusetts.
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Division of Immunology, Children's Hospital, Boston, Massachusetts.
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Division of Immunology, Children's Hospital, Boston, Massachusetts.
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Division of Immunology, Children's Hospital, Boston, Massachusetts.
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Published March 1, 1994 - More info
The ligand for CD40 is expressed on activated T lymphocytes and delivers contact-dependent activation signals to B lymphocytes. The mechanisms regulating CD40 ligand gene expression are largely unknown. Optimal expression of CD40 ligand required activation of protein kinase C and a rise in intracellular calcium concentration. CD40 ligand expression was inhibited by pretreatment of T cells with cyclosporin A. Cyclosporin A analogues inhibited CD40 ligand expression with a potency mirroring the ability of each compound to inhibit calcineurin activity, indicating that calcineurin plays a key role in CD40 ligand gene expression. Cyclosporin A inhibited IL-4-driven CD40 ligand-dependent IgE isotype switching in PBMC but did not inhibit IgE synthesis induced by CD40 mAb plus IL-4. PBMC derived from transplant patients receiving cyclosporin A failed to express CD40 ligand upon stimulation. These results suggest that patients receiving cyclosporin A may be deficient in CD40 ligand-dependent T cell help.
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