Glucocorticoids upregulate CD40 ligand expression and induce CD40L-dependent immunoglobulin isotype switching

Area of Science:

• Immunology
• Molecular Biology

Background:

• Interleukin-4 (IL-4) and CD40 ligation are critical for B cell immunoglobulin E (IgE) synthesis.
• Hydrocortisone (HC) was previously shown to induce IgE synthesis in IL-4-stimulated human B cells.

Discussion:

• HC-induced IgE synthesis is dependent on CD40 ligand (CD40L) interactions, as demonstrated by the failure to induce IgE in CD40L-deficient B cells.
• Soluble CD40-Ig fusion protein and anti-CD40L monoclonal antibody (mAb) blocked HC's capacity to induce IgE synthesis in normal B cells.
• HC upregulates CD40L mRNA and surface expression in peripheral blood mononuclear cells (PBMCs), T cells, and B cells.

Key Insights:

• HC upregulates CD40L mRNA expression in PBMCs within 3 hours, an effect inhibited by actinomycin D.
• The steroid hormone receptor antagonist RU-486 inhibits both HC-induced CD40L mRNA upregulation and IgE synthesis.
• Ligand-mediated activation of the glucocorticoid receptor is responsible for upregulating CD40L expression in human lymphocytes.

Outlook:

• Further research could explore the precise molecular mechanisms linking glucocorticoid receptor activation to CD40L expression.
• Understanding this pathway may offer new therapeutic targets for IgE-mediated allergic diseases.
• Investigating the role of CD40L in other glucocorticoid-regulated immune responses is warranted.